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Nerve repair and regeneration are still challenging issues in the world, mainly due to the complex anatomic structure and limited regeneration ability of natural nerves. Tissue engineering provides a structure and function similar to nerve tissue through scaffold materials, seed cells, and active factors, which is a promising method to treat nerve injury. Gelatin methacrylate (GelMA) hydrogel is a kind of gelatin modified by methacrylamide, which possesses adjustable mechanical properties, convenient processability, and excellent biocompatibility, has been widely used in nerve tissue engineering. In this paper, the research progress of GelMA-based hydrogel in nerve repair and regeneration in recent five years is reviewed, with emphasis on the advanced manufacturing technologies of three-dimensional (3D) GelMA scaffold and the application systems that can effectively promote nerve repair and regeneration. We also evaluated the challenges and prospects of GelMA-based hydrogels in the field of nerve repair and regeneration, which is of guiding significance to the research of nerve tissue engineering. [ABSTRACT FROM AUTHOR]

Safe and accurate in situ delivery of biocompatible materials is a fundamental requirement for many biomedical applications. These include sustained and local drug release, implantation of acellular biocompatible scaffolds, and transplantation of cells and engineered tissues for functional restoration of damaged tissues and organs. The common practice today includes highly invasive operations with major risks of surgical complications including adjacent tissue damage, infections, and long healing periods. In this work, a novel non‐invasive delivery method is presented for scaffold, cells, and drug delivery deep into the body to target inner tissues. This technology is based on acousto‐sensitive materials which are polymerized by ultrasound induction through an external transducer in a rapid and local fashion without additional photoinitiators or precursors. The applicability of this technology is demonstrated for viable and functional cell delivery, for drug delivery with sustained release profiles, and for 3D printing. Moreover, the mechanical properties of the delivered scaffold can be tuned to the desired target tissue as well as controlling the drug release profile. This promising technology may shift the paradigm for local and non‐invasive material delivery approach in many clinical applications as well as a new printing method – "acousto‐printing" for 3D printing and in situ bioprinting. [ABSTRACT FROM AUTHOR]

Highlights: This review provides a comprehensive summary associated with recent progress in the preparation and application of microgels. The characteristics and applications of microgels and microgel-based scaffolds for cell culture and delivery are elaborated with an emphasis on the advantages of these carriers in cell therapy. This review expounds on the ongoing and foreseeable applications and current limitations of microgels and their aggregate in the field of biomedical engineering. Through stimulating innovative ideas, the present review paves new avenues for expanding the application of microgels in cell delivery techniques. Microgels prepared from natural or synthetic hydrogel materials have aroused extensive attention as multifunctional cells or drug carriers, that are promising for tissue engineering and regenerative medicine. Microgels can also be aggregated into microporous scaffolds, promoting cell infiltration and proliferation for tissue repair. This review gives an overview of recent developments in the fabrication techniques and applications of microgels. A series of conventional and novel strategies including emulsification, microfluidic, lithography, electrospray, centrifugation, gas-shearing, three-dimensional bioprinting, etc. are discussed in depth. The characteristics and applications of microgels and microgel-based scaffolds for cell culture and delivery are elaborated with an emphasis on the advantages of these carriers in cell therapy. Additionally, we expound on the ongoing and foreseeable applications and current limitations of microgels and their aggregate in the field of biomedical engineering. Through stimulating innovative ideas, the present review paves new avenues for expanding the application of microgels in cell delivery techniques. [ABSTRACT FROM AUTHOR]

Allogeneic tumor cell vaccines provide off‐the‐shelf convenience but lack patient specificity due to heterogeneity in tumor antigens. Here, allogeneic tumor cell corpses are converted into "zombie cells" capable of assimilating heterogeneous tumor by seizing cancer cells and spreading adjuvant infection. This causes pseudo‐oncolysis of tumors, transforming them into immunogenic targets for enhanced phagocytosis. It is shown that in postoperative tumor models, localized delivery of premade "zombie cells" through stepwise gelation in resection cavity consolidates tumor surgery. Compared to analogous vaccines lacking "seizing" or "assimilating" capability, "zombie cell" platform effectively mobilizes T cell response against residual tumors, and establishes immunological memory against tumor re‐challenge, showing less susceptibility to immune evasion. Despite using allogeneic sources, "zombie cell" platform functions as generalizable framework to produce long‐term antitumor immunity in different tumor models, showing comparable effect to autologous vaccine. Together, with the potential of off‐the‐shelf availability and personalized relevance to heterogenous tumor antigens, this study suggests an alternative strategy for timely therapy after tumor surgery. [ABSTRACT FROM AUTHOR]

Mesenchymal stromal cells (MSCs) have displayed potential in regenerating organ function due to their anti-fibrotic, anti-inflammatory, and regenerative properties. However, there is a need for delivery systems to enhance MSC retention while maintaining their anti-fibrotic characteristics. This study investigates the feasibility of using alginate hydrogel microstrands as a cell delivery vehicle to maintain MSC viability and phenotype. To accommodate cell implantation needs, we invented a Syringe-in-Syringe approach to reproducibly fabricate microstrands in small numbers with a diameter of around 200 µm and a porous structure, which would allow for transporting nutrients to cells by diffusion. Using murine NIH 3T3 fibroblasts and primary embryonic 16 (E16) salivary mesenchyme cells as primary stromal cell models, we assessed cell viability, growth, and expression of mesenchymal and fibrotic markers in microstrands. Cell viability remained higher than 90% for both cell types. To determine cell number within the microstrands prior to in vivo implantation, we have further optimized the alamarBlue assay to measure viable cell growth in microstrands. We have shown the effect of initial cell seeding density and culture period on cell viability and growth to accommodate future stromal cell delivery and implantation. Additionally, we confirmed homeostatic phenotype maintenance for E16 mesenchyme cells in microstrands. [ABSTRACT FROM AUTHOR]

Poly(lactic-glycolic acid) (PLGA) is a biocompatible bio-scaffold material, but its own hydrophobic and electrically neutral surface limits its application as a cell scaffold. Polymer materials, mimics ECM materials, and organic material have often been used as coating materials for PLGA cell scaffolds to improve the poor cell adhesion of PLGA and enhance tissue adaptation. These coating materials can be modified on the PLGA surface via simple physical or chemical methods, and coating multiple materials can simultaneously confer different functions to the PLGA scaffold; not only does this ensure stronger cell adhesion but it also modulates cell behavior and function. This approach to coating could facilitate the production of more PLGA-based cell scaffolds. This review focuses on the PLGA surface-modified materials, methods, and applications, and will provide guidance for PLGA surface modification. [ABSTRACT FROM AUTHOR]

Stem cells play critical roles in cell therapies and tissue engineering for nerve repair. However, achieving effective delivery of high cell density remains a challenge. Here, a novel cell delivery platform termed the hyper expansion scaffold (HES) is developed to enable high cell loading. HES facilitated self‐promoted and efficient cell absorption via a dual driving force model. In vitro tests revealed that the HES rapidly expanded 80‐fold in size upon absorbing 2.6 million human amniotic epithelial stem cells (hAESCs) within 2 min, representing over a 400% increase in loading capacity versus controls. This enhanced uptake benefited from macroscopic swelling forces as well as microscale capillary action. In spinal cord injury (SCI) rats, HES–hAESCs promoted functional recovery and axonal projection by reducing neuroinflammation and improving the neurotrophic microenvironment surrounding the lesions. In summary, the dual driving forces model provides a new rationale for engineering hydrogel scaffolds to facilitate self‐promoted cell absorption. The HES platform demonstrates great potential as a powerful and efficient vehicle for delivering high densities of hAESCs to promote clinical treatment and repair of SCI. [ABSTRACT FROM AUTHOR]

Cell-based therapeutics are novel therapeutic strategies that can potentially treat many presently incurable diseases through novel mechanisms of action. Cell therapies may benefit from the ease, safety, and efficacy of administering therapeutic cells. Despite considerable recent technological and biological advances, several barriers remain to the clinical translation and commercialization of cell-based therapies, including low patient compliance, personal handling inconvenience, poor biosafety, and limited biocompatibility. Microneedles (MNs) are emerging as a promising biomedical device option for improved cell delivery with little invasion, pain-free administration, and simplicity of disposal. MNs have shown considerable promise in treating a wide range of diseases and present the potential to improve cell-based therapies. In this review, we first summarized the latest advances in the various types of MNs developed for cell delivery and cell sampling. Emphasis was given to the design and fabrication of various types of MNs based on their structures and materials. Then we focus on the recent biomedical applications status of MNs-mediated cell delivery and sampling, including tissue repair (wound healing, heart repair, and endothelial repair), cancer treatment, diabetes therapy, cell sampling, and other applications. Finally, the current status of clinical application, potential perspectives, and the challenges for clinical translation are also highlighted. [Display omitted] [ABSTRACT FROM AUTHOR]

Cell transplants in therapeutic studies do not preserve their long-term function inside the donor body. In mesenchymal stem cell (MSC) transplants, transplanted cells disperse through the body and are prone to degradation by immune cells after the transplant process. Various strategies, such as usage of the immunosuppressive drugs to eliminate allograft rejection, are designed to increase the efficiency of cell therapy. Another strategy is the construction of biomimetic encapsulates using polymeric materials, which isolate stem cells and protect them from environmental effects. In this study, fibroblasts (L929) and MSCs were investigated for their improved viability and functionality once encapsulated inside the alginate microbeads under in vitro conditions for up to 12 days of incubation. Thus, uniform and injectable (<200 µm) cell-loaded microbeads were constructed by the electrostatically assisted spraying technique. Results showed that both L929 and MSCs cells continue their metabolic activity inside the microbeads during the incubation periods. Glucose consumption and lactic acid production levels of both cell lines were consistently observed. The released cell number on day 12 was found to be increased compared to day 0. Protein expression levels of both groups increased every day with the expected doubling rate. Hence, this strategy with a simple yet clever design to encapsulate either MSCs or L929 cells might outstand as a potential cell delivery platform for cell therapy-based tissue engineering. [ABSTRACT FROM AUTHOR]

Gene delivery has emerged as a promising alternative to conventional treatment approaches, allowing for the manipulation of gene expression through gene insertion, deletion, or alteration. However, the susceptibility of gene delivery components to degradation and challenges associated with cell penetration necessitate the use of delivery vehicles for effective functional gene delivery. Nanostructured vehicles, such as iron oxide nanoparticles (IONs) including magnetite nanoparticles (MNPs), have demonstrated significant potential for gene delivery applications due to their chemical versatility, biocompatibility, and strong magnetization. In this study, we developed an ION-based delivery vehicle capable of releasing linearized nucleic acids (tDNA) under reducing conditions in various cell cultures. As a proof of concept, we immobilized a CRISPR activation (CRISPRa) sequence to overexpress the pink1 gene on MNPs functionalized with polyethylene glycol (PEG), 3-[(2-aminoethyl)dithio]propionic acid (AEDP), and a translocating protein (OmpA). The nucleic sequence (tDNA) was modified to include a terminal thiol group and was conjugated to AEDP's terminal thiol via a disulfide exchange reaction. Leveraging the natural sensitivity of the disulfide bridge, the cargo was released under reducing conditions. Physicochemical characterizations, including thermogravimetric analysis (TGA) and Fourier-transform infrared (FTIR) spectroscopy, confirmed the correct synthesis and functionalization of the MNP-based delivery carriers. The developed nanocarriers exhibited remarkable biocompatibility, as demonstrated by the hemocompatibility, platelet aggregation, and cytocompatibility assays using primary human astrocytes, rodent astrocytes, and human fibroblast cells. Furthermore, the nanocarriers enabled efficient cargo penetration, uptake, and endosomal escape, with minimal nucleofection. A preliminary functionality test using RT-qPCR revealed that the vehicle facilitated the timely release of CRISPRa vectors, resulting in a remarkable 130-fold overexpression of pink1. We demonstrate the potential of the developed ION-based nanocarrier as a versatile and promising gene delivery vehicle with potential applications in gene therapy. The developed nanocarrier is capable of delivering any nucleic sequence (up to 8.2 kb) once it is thiolated using the methodology explained in this study. To our knowledge, this represents the first MNP-based nanocarrier capable of delivering nucleic sequences under specific reducing conditions while preserving functionality. [ABSTRACT FROM AUTHOR]

This work aims to engineer a new stable injectable Mn-based methacrylated gellan gum (Mn/GG-MA) hydrogel for real-time monitored cell delivery into the central nervous system. To enable the hydrogel visualization under Magnetic Resonance Imaging (MRI), GG-MA solutions were supplemented with paramagnetic Mn2+ ions before its ionic crosslink with artificial cerebrospinal fluid (aCSF). The resulting formulations were stable, detectable by T1-weighted MRI scans and also injectable. Cell-laden hydrogels were prepared using the Mn/GG-MA formulations, extruded into aCSF for crosslink, and after 7 days of culture, the encapsulated human adipose-derived stem cells remained viable, as assessed by Live/Dead assay. In vivo tests, using double mutant MBPshi/shi/rag2 immunocompromised mice, showed that the injection of Mn/GG-MA solutions resulted in a continuous and traceable hydrogel, visible on MRI scans. Summing up, the developed formulations are suitable for both non-invasive cell delivery techniques and image-guided neurointerventions, paving the way for new therapeutic procedures. [ABSTRACT FROM AUTHOR]

Marine organisms provide novel and broad sources for the preparations and applications of biomaterials. Since the urgent requirement of bio‐hydrogels to mimic tissue extracellular matrix (ECM), the natural biomacromolecule hydrogels derived from marine sources have received increasing attention. Benefiting from their outstanding bioactivity and biocompatibility, many attempts have been made to reconstruct ECM components by applying marine‐derived natural hydrogels. Moreover, marine hydrogels have been successfully applied in biomedicine by means of microfluidics, electrospray, and bioprinting. In this review, the classification and characteristics of marine‐derived hydrogels are summarized. In particular, their role in the development of biomaterials is also introduced. Then, the recent advances in bio‐fabrication strategies for various hydrogel materials are focused upon. Besides, the influences of hydrogel types on their functions in biomedical applications are discussed in depth. Finally, critical reflections on the limitations and future development of marine‐derived hydrogels are presented. [ABSTRACT FROM AUTHOR]

[Display omitted] • Temperature-responsive microparticle swimmers for cell manipulation. • Bio-friendly surface assembly with morphology induction and temperature cycling. • Temperature sensitivity enables controlled gelatin layer manipulation and cell interaction. • Creation of time-specific, shape-specific, and patterned heterotypic cell co-culture models.. Developing biocompatible and flexible cell manipulation tools is crucial for effective cell delivery in tissue engineering. Herein, thermo-responsive microparticle swimmers, composed of an alginate core and a rough gelatin surface, are developed as a tool for remote cell manipulation and the construction of patterned cell models. The microparticles are fabricated using a novel bio-friendly surface assembly strategy, which leverages morphology-induced gelatin adsorption combined with temperature-cycling crosslinking to deposit multiple gelatin layers onto microfluidic-derived rough microparticles. Gelatin molecules can adsorb onto the rough surface at 25 °C and become cross-linked at 4 °C to form a stable coating layer while preserving the coarse morphology for additional assembly cycles. The gelatin layers remain intact at room temperature for cell loading and transport, but rapidly dissipate at 37 °C, enabling cell release. Moreover, complex manipulations of living cell populations, such as remote tweezing, can be achieved by the introduction of magneto-responsive moieties. These versatile microparticles provide an efficient tool for the in vitro construction of flexible and dynamic patterned cell models, with promising applications in tissue engineering, drug screening, and organoid development. [ABSTRACT FROM AUTHOR]

Mesenchymal stem cells (MSC) are currently being investigated for their therapeutic applications in a wide range of diseases. Although many studies examined peripheral venous administration of MSC, few have investigated the detailed intravenous administration procedures of MSC from their preparation until they enter the body. The current study therefore aimed to explore the most efficient infusion procedure for MSC delivery by preparing and infusing them under various conditions. Canine adipose-derived mesenchymal stem cells (cADSC) were infused using different infusion apparatuses, suspension solutions, allogenic serum supplementation, infusion time and rates, and cell densities, respectively. Live and dead cell counts were then assessed by manual measurements and flow cytometry. Efficiency of live- and dead-cell infusion and cell viability were calculated from the measured cell counts and compared under each condition. Efficiency of live-cell infusion differed significantly according to the infusion apparatus, infusion rate, and combination of cell density and serum supplementation. Cell viability after infusion differed significantly between the infusion apparatuses. The optimal infusion procedure resulting in the highest cell delivery and viability involved suspending cADSC in normal saline supplemented with 5% allogenic serum at a density of 5 × 105 cells/mL, and infusing them using an automatic infusion device for 15 min. This procedure is therefore recommended as the standard procedure for the intravenous administration of ADSC in terms of cell-delivery efficiency. [ABSTRACT FROM AUTHOR]

In this study, we present an in situ microfluidic system to precisely control highly porous polycaprolactone microspheres as tissue templates for tissue engineering. The porosity of the microspheres was controlled by adjusting the flow rates of the polymer phase and the pore-generating material phase in the dispersed phase. The microfluidic flow-focusing technique was adopted to manufacture porous microspheres using a relatively highly viscous polymer solution, and the device was fabricated by conventional photolithography and PDMS casting. The fabricated in situ microfluidic system was used to precisely control the pore size of monodispersed polycaprolactone microspheres. The porous microspheres with controlled pore sizes were evaluated by culturing HDF cells on the surface of porous microspheres and injection into the subcutaneous tissue of rats. We found that the increased pore size of the microspheres improved the initial proliferation rate of HDF cells after seeding and relieved the inflammatory response after the implantation of porous microspheres in the subcutaneous tissue of rats. [ABSTRACT FROM AUTHOR]

Albumin is a natural biomaterial that is abundantly available in blood and body fluids. It is clinically used as a plasma expander, thereby increasing the plasma thiol concentration due to its cysteine residues. Albumin is a regulator of intervascular oncotic pressure, serves as an anti-inflammatory modulator, and it has a buffering role due to its histidine imidazole residues. Because of its unique biological and physical properties, albumin has also emerged as a suitable biomaterial for coating implantable devices, for cell and drug delivery, and as a scaffold for tissue engineering and regenerative medicine. As a biomaterial, albumin can be used as surface-modifying film or processed either as cross-linked protein gels or as electrospun fibers. Herein we have discussed how albumin protein can be utilized in regenerative medicine as a hydrogel and as a fibrous mat for a diverse role in successfully delivering drugs, genes, and cells to targeted tissues and organs. The review of prior studies indicated that albumin is a tunable biomaterial from which different types of scaffolds with mechanical properties adjustable for various biomedical applications can be fabricated. Based on the progress made to date, we concluded that albumin-based device coatings, delivery of drugs, genes, and cells are promising strategies in regenerative and personalized medicine. [ABSTRACT FROM AUTHOR]

Human-adipose-derived mesenchymal stem cells (hADMSCs) are adult stem cells and are relatively easy to access compared to other sources of mesenchymal stem cells (MSCs). They have shown immunomodulation properties as well as effects in improving tissue regeneration. To better stimulate and preserve the therapeutic properties of hADMSCs, biomaterials for cell delivery have been studied extensively. To date, hyaluronic acid (HA)-based materials have been most widely adopted by researchers around the world. PGmatrix is a new peptide-based hydrogel that has shown superior functional properties in 3D cell cultures. Here, we reported the in vitro and in vivo functional effects of PGmatrix on hADMSCs in comparison with HA and HA-based Hystem hydrogels. Our results showed that PGmatrix was far superior in maintaining hADMSC viability during prolonged incubation and stimulated expression of SSEA4 (stage-specific embryonic antigen-4) in hADMSCs. hADMSCs encapsulated in PGmatrix secreted more immune-responsive proteins than those in HA or Hystem, though similar VEGF-A and TGFβ1 release levels were observed in all three hydrogels. In vivo studies revealed that hADMSCs encapsulated with PGmatrix showed improved skin wound healing in diabetic-induced mice at an early stage, suggesting possible anti-inflammatory effects, though similar re-epithelialization and collagen density were observed among PGmatrix and HA or Hystem hydrogels by day 21. [ABSTRACT FROM AUTHOR]

• Live Cell delivery of Cell-penetrating peptides was investigated with Hela cells. • In terms of charge, the number of arginines (R5) or lysine (K2R3) was varied. • Presence of -OH in the aliphatic backbone (S2R3) or aromatic backbone (Y2R3) was also considered. • The influence of aromaticity (F2R3) was considered, and R5 was the best among them. Cell-penetrating peptides (CPPs) are handy tools for protein/peptide delivery, thus helping in protein therapeutics, understanding versatile protein mechanisms etc. Indeed, CPP attached to the target protein, which is otherwise not cell permeable, can be delivered to the cell. To explore the role of CPPs in cell delivery, this work will investigate the effect of different CPP scaffolds on cellular uptake. Thus, a poly-arginine (Arg, R) based small CPP is synthesised. Linear R5 was chosen as the model CPP modified to K2R3 (Lys, K) to explore the influence of Arg-within the scaffold. G2R3 (Gly, G) probs the influence of charge as it failed to pass the membrane. To investigate the effect of aromaticity in cellular uptake, F2R3 (Phe, F) was synthesised, which was later modified to Y2R3 (Tyr, Y) to explore the effect of aromaticity along with active -OH groups. S2R3 (Ser, S) was designed to investigate the sole influence of -OH groups in cell delivery. Experiments suggest that R5 outperforms other peptides in cell delivery and was further examined at 37 °C and 4 °C. Successful cell delivery of R5 at 4 °C rules out chances of any energy-dependent cellular uptake pathway, including endocytosis. The probable structural influence of R5 and K2R3 was also investigated using DFT calculation. [Display omitted] [ABSTRACT FROM AUTHOR]

BACKGROUND: Self-healing hydrogels are scaffold materials with superior self-healing capability and biocompatibility, and are widely used in bone tissue engineering. OBJECTIVE: To introduce the gelatin mechanism and composition of self-healing hydrogels and summarize their applications in bone tissue engineering. METHODS: The first author searched both Chinese and English articles with key words "self-healing hydrogels; bone tissue engineering; bone regeneration" on CNKl, Wanfang, VIP, PubMed, Embase and Web of Science databases published from 2000 to 2020. Totally 69 eligible articles were selected for review. RESULTS AND CONCLUSION: The gelation mechanisms of self-healing hydrogels include dynamic covalent bonds, supramolecular bonds and multi-mechanism cross-links. Self-healing hydrogels can be composed of natural polymers, synthetic polymers and nanocomposites. Self-healing hydrogels have been found to be applied in bone tissue engineering through scaffold modification as stem cells delivery vehicle. The application of self-healing hydrogels in bone tissue engineering can be broaden by enhancing the mechanical properties of the hydrogel while maintaining its self-healing capability. Additionally, the specific mechanism for better superiority of self-repairing hydrogels over traditional hydrogels in bone tissue engineering is still unclear. [ABSTRACT FROM AUTHOR]

Micro/nanorobots have attracted significant interest in the biomedical field due to their micro/nano scale sizes and autonomously untethered motions. Meanwhile, stem cell‐based therapy has emerged as a promising approach to cure previously irreparable degenerative diseases by virtue of the stem cells' differentiation and regeneration. To ensure the efficiency of the stem cell delivery, developing suitable and reliable cell‐transport systems is essential. Micro/nanorobots aimed at cell transport have progressed in recent years, which can perform this crucial step of cell delivery accurately and noninvasively during cell‐based therapy. Herein, a review of the design and fabrication technologies and actuation mechanisms of cell‐transport microrobots is presented. The applications of the micro/nanorobotic cell‐manipulation and cell‐transport platforms are discussed, as well as the current challenges and the future perspectives in translation of microrobots from research stage to clinical applications. [ABSTRACT FROM AUTHOR]

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system. This disorder may cause progressive and permanent impairment, placing significant physical and psychological strain on sufferers. Each progress in MS therapy marks a significant advancement in neurological research. Hydrogels can serve as a scaffold with high water content, high expansibility, and biocompatibility to improve MS cell proliferation in vitro and therapeutic drug delivery to cells in vivo. Hydrogels may also be utilized as biosensors to detect MS-related proteins. Recent research has employed hydrogels as an adjuvant imaging agent in immunohistochemistry assays. Following an overview of the development and use of hydrogels in MS diagnostic and therapy, this review discussed hydrogel's advantages and future opportunities in the diagnosis and treatment of MS. [ABSTRACT FROM AUTHOR]

Chimeric antigen receptor T cell (CAR T) therapy was a milestone in the treatment of relapsed and refractory B cell malignancies. However, beneficial effects of CAR T cells have not been obtained in solid tumors yet. Herein, we implement a porous microneedle patch that accommodates CAR T cells and allows in situ penetration-mediated seeding of CAR T cells when implanted in the tumor bed or in the post-surgical resection cavity. CAR T cells loaded in the pores of the microneedle tips were readily escorted to the tumor in an evenly scattered manner without losing their activity. Such microneedle-mediated local delivery enhanced infiltration and immunostimulation of CAR T cells as compared to direct intratumoral injection. This tailorable patch offers a transformative platform for scattered seeding of living cells for treating a variety of tumors. [ABSTRACT FROM AUTHOR]

Cell delivery of therapeutic macromolecules and nanoparticles is a critical drug development challenge. Translocation through lipid raft-mediated endocytic mechanisms is being sought, as it can avoid rapid lysosomal degradation. Here, we present a set of short α/β-peptide tags with high affinity to the lipid raft-associated ganglioside GM1. These sequences induce effective internalization of the attached immunoglobulin cargo. The structural requirements of the GM1-peptide interaction are presented, and the importance of the membrane components are shown. The results contribute to the development of a receptor-based cell delivery platform. [ABSTRACT FROM AUTHOR]

Mesenchymal stem cells (MSCs) are so far the most widely researched stem cells in clinics and used as an experimental cellular therapy module, particularly in cardiac regeneration and repair. Ever since the discovery of cardiomyogenesis induction in MSCs, a wide variety of differentiation protocols have been extensively used in preclinical models. However, pre differentiated MSC-derived cardiomyocytes have not been used in clinical trials; highlighting discrepancies and limitations in its use as a source of derived cardiomyocytes for transplantation to improve the damaged heart function. Therefore, this review article focuses on the strategies used to derive cardiomyocytes-like cells from MSCs isolated from three widely used tissue sources and their differentiation efficiencies. We have further discussed the role of MSCs in inducing angiogenesis as a cellular precursor to endothelial cells and its secretory aspects including exosomes. We have then discussed the strategies used for delivering cells in the damaged heart and how its retention plays a critical role in the overall outcome of the therapy. We have also conversed about the scope of the local and systemic modes of delivery of MSCs and the application of biomaterials to improve the overall delivery efficacy and function. We have finally discussed the advantages and limitations of cell delivery to the heart and the future scope of MSCs in cardiac regenerative therapy. [ABSTRACT FROM AUTHOR]

This paper presents a new thermal sensitive hydrogel system based on cystamine-functionalised sodium alginate-g-pluronic F127 (ACP). The introduction of cystamine to the alginate backbone not only creates a covalent bond with pluronic F127 but also provides intrinsic anti-bacterial activity for the resultant hydrogel. The amount of water uptake inside the hydrogel remained ~200% for 6 days and the degradation was completed in 12 days in physiological media. The ACP copolymer solution could form a hydrogel at body temperature (~37 °C) and could return to the solution phase if the temperature decreased below 25o °C. Fibroblast encapsulated in situ in the ACP hydrogel maintained their viability (≥90% based on the live/dead assay) for 7 days, demonstrating the good biocompatibility of the ACP hydrogel for long-term cell cultivation. In addition, three-dimensional (3D) culture showed that fibroblast attached to the hydrogels and successfully mimicked the porous structure of the ACP hydrogel after 5 days of culture. Fibroblast cells could migrate from the cell-ACP clusters and form a confluent cell layer on the surface of the culture dish. Altogether, the obtained results indicate that the thermal-responsive ACP hydrogel synthesised in this study may serve as a cellular delivery platform for diverse tissue engineering applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Microfluidic hydrogel microspheres have been broadly studied across a wide range of industries and applications, and their use in the medical field, including control cells and drug delivery, is increasing. The usual design of these materials is intended to enable the efficient and smart encapsulation of cells and/or drugs in microspheres in which the functionalities and features are effectively controlled, lending itself some unique properties. These characteristics promote exchanges and cooperation in multiple disciplines and boost the development of precision medicine, new manufacturing technologies, and applied materials. This review begins with a discussion of microfluidic hydrogel microspheres and then introduces the preparation equipment, main principles, and related characteristics of the microspheres. Furthermore, the medical applications of microfluidic hydrogel microspheres for delivering cells and drugs are emphasized. Finally, this review discusses perspectives and future directions for accelerating the development and application of microfluidic hydrogel microspheres for controlled delivery. [ABSTRACT FROM AUTHOR]

Immunotherapy is leading a paradigm shift in the treatment of various diseases, including tumors, auto‐immune diseases, and infectious diseases. However, the limited response rate and systemic side effects significantly impede the clinical applications of immunotherapy. As natural carriers for proteins and molecules, cells with low immunogenicity and toxicity have attracted considerable attention for biomedical applications and have achieved encouraging progress especially in immunotherapy. The convergence of multiple disciplines has equipped cell‐based delivery systems with control over their spatiotemporal distribution to enhance treatment efficacy and reduce side effects. Here, an overview of the fundamentals and design principles of cell‐based delivery systems followed by a perspective that includes the most recent advances of various cells as delivery carriers, with a special focus on the implications of cell‐based delivery systems for immunotherapy is offered. [ABSTRACT FROM AUTHOR]

Adipose-derived stem cells (ADSCs) have been widely researched and used as a drug therapy in many fields like disease treatment and tissue engineering. However, ADSCs are susceptible to the surrounding environment. The emergence of acellular extracellular matrix provides a solution, which can serve as biomaterial scaffold as well as original ecological niche for the stem cells. Therefore, we propose the hypothesis that human decellularized adipose tissues (hDAT) are processed into injectable hydrogels and then mixed evenly with ADSCs. So that the ADSCs embedded-hydrogels could directly carry the stem cells to the appropriate sites. The hDAT hydrogel could provide microenvironmental protection for ADSCs. In this study, we successfully made human decellularized adipose tissue hydrogel (hDAT-gel), which was temperature-sensitive, liquid at 4°C and semi-solid at 37°C. When the ADSCs were embedded in hDAT-gel, they survived well and continued to grow well in layers. When the pre-gel containing ADSCs was injected subcutaneously into nude mice, the sample results after 15 min showed gelation occurred in situ. These results suggested that hDAT-gel could provide a culture platform for ADSCs delivery. [ABSTRACT FROM AUTHOR]

Background: Mesenchymal stem cell transplantation is an emerging therapy for treating acute and chronic I iver diseases as an alternative for patients who are not transplant candidates. The potential of this treatment depends on its therapeutic efficiency and safety, which have been investigated and evaluated in both preclinical and clinical settings. However, there are still some risks associated with the delivery methods, such as low long-term retention rate and the possibility of arousing cancer or rejection. Methods: During the review process, previous papers mentioning "stem cell treatment"and "liver diseases" were searched. We described different up-to-date approaches for stem cells from various origins to be delivered to the liver and compared respectively their pros and cons for clinical applications. We also proposed several potential techniques for future studies. Summary: An efficient and safe stem cell delivery could be enabled via Alginate-Polylysine-Alginate (APA) microencapsulation, lipid-conjugated coating or the use of nanoparticles. Their efficacy will be improved through tissue engineering and microrobots as the delivery is sustained and targeted with fewer rejection responses. [ABSTRACT FROM AUTHOR]

Background: In recent years, adipose-derived stromal cells (ASCs) have been heavily studied for soft tissue regeneration, augmentation, and dermal wound healing. Methods: In this review, we investigated the trends in injectable scaffolds for ASC delivery in the dermis, and injectable or implantable scaffolds for ASC delivery in the subcutis. A total of 547 articles were screened across three databases; of these, 22 studies were found to be eligible and were included. The scaffolds were subdivided and analyzed based on their tissue placement (dermis or subcutis), delivery method (injected or implanted), and by the origin of the materials (natural, synthetic, and combinatory). Results: ASCs embedded in scaffolds generally showed improved viability. Neovascularization in the transplanted tissue was greater when undifferentiated ASCs were embedded in a combinatory scaffold or if differentiated ASCs were embedded in a natural scaffold. ASCs embedded in natural materials underwent more adipogenic differentiation than ASCs embedded in synthetic scaffolds, indicating an etiologically unknown difference that has yet to be described. Increased mechanical strength of the scaffold material correlated with improved outcome measurements in the investigated studies. Wound healing studies reported reduced healing time in all except one article due to contraction of the control wounds. Conclusions: In future clinical trials, we recommend embedding ASCs in injectable and implantable scaffolds for enhanced protection, retained viability, and improved therapeutic effects. Trial registration: This review was registered with PROSPERO: ID=CRD42020171534. The use of scaffolds as a vehicle for ASC delivery generally improved cell viability, angiogenesis, and wound healing in vivo compared to utilizing ASCs alone. ASCs embedded in natural materials induced more adipogenesis than ASCs embedded in synthetic materials. Adipogenic-induced ASCs further increased this effect. The included studies indicate that the seeded scaffold material influences the differentiation of ASCs in vivo. All studies investigating the mechanical strength of ASC scaffolds reported improved outcome measurements with improved mechanical strength. The results suggest that scaffolds, in general, are favorable for ASC delivery. We recommend initiating clinical studies using scaffolds based on mechanical properties and tunability to improve ASC viability. For fat regeneration, natural scaffolds are recommended. [ABSTRACT FROM AUTHOR]

Adipose-derived stem cells (ADSCs) have been widely researched and used as a drug therapy in many fields like disease treatment and tissue engineering. However, ADSCs are susceptible to the surrounding environment. The emergence of acellular extracellular matrix provides a solution, which can serve as biomaterial scaffold as well as original ecological niche for the stem cells. Therefore, we propose the hypothesis that human decellularized adipose tissues (hDAT) are processed into injectable hydrogels and then mixed evenly with ADSCs. So that the ADSCs embedded-hydrogels could directly carry the stem cells to the appropriate sites. The hDAT hydrogel could provide microenvironmental protection for ADSCs. In this study, we successfully made human decellularized adipose tissue hydrogel (hDAT-gel), which was temperature-sensitive, liquid at 4°C and semi-solid at 37°C. When the ADSCs were embedded in hDAT-gel, they survived well and continued to grow well in layers. When the pre-gel containing ADSCs was injected subcutaneously into nude mice, the sample results after 15 min showed gelation occurred in situ. These results suggested that hDAT-gel could provide a culture platform for ADSCs delivery. [ABSTRACT FROM AUTHOR]

Despite excellent processing and biological properties of gelatin for use as a cell carrier, none of the gelatin‐based hydrogel cell carriers reported to date offer all characteristics including quick formation, injectability, self‐healing, and durability, which are simultaneously required for an ideal system. Here, a gelatin‐based hydrogel with dynamic Schiff base linkages, so‐called "dynamic hydrogel," as an injectable cell carrier consisting of gelatin and amylopectin multiple aldehyde (AMPA), with all the required characteristics is reported. Biocompatibility and osteoinductivity of the hydrogel are verified through the culture of human bone marrow‐derived mesenchymal stem cells (hBMSCs). As live/dead results show, hBMSCs are alive and highly viable ≈85–90% within the hydrogel after 5 days. According to bromodeoxyuridine cell proliferation assay, a significant increase in the number of the cells seeded in the hydrogel confirms its clinical significance for cell therapy. Most importantly, histological visualization using Mason's Trichrome staining indicates secretion of extracellular matrix around the cells loaded in the hydrogel and also expression level evaluation of the crucial osteogenic markers, confirms that the hydrogel can provide osteoinductive support for osteocyte differentiation of hBMSCs after 14 days. Therefore, this hydrogel provides more progress on the path toward bone tissue engineering and further treatment of bone diseases. [ABSTRACT FROM AUTHOR]

There is a pressing need to develop ways to deliver therapeutic macromolecules to their intracellular targets. Certain viral and bacterial proteins are readily internalized in functional form through lipid raft‐mediated/caveolar endocytosis, but mimicking this process with protein cargoes at therapeutically relevant concentrations is a great challenge. Targeting ganglioside GM1 in the caveolar pits triggers endocytosis. A pentapeptide sequence WYKYW is presented, which specifically captures the glycan moiety of GM1 (KD = 24 nm). The WYKYW‐tag facilitates the GM1‐dependent endocytosis of proteins in which the cargo‐loaded caveosomes do not fuse with lysosomes. A structurally intact immunoglobulin G complex (580 kDa) is successfully delivered into live HeLa cells at extracellular concentrations ranging from 20 to 160 nm, and escape of the cargo proteins to the cytosol is observed. The short peptidic WYKYW‐tag is an advantageous endocytosis routing sequence for lipid raft‐mediated/caveolar cell delivery of therapeutic macromolecules, especially for cancer cells that overexpress GM1. [ABSTRACT FROM AUTHOR]

Soft organisms such as earthworms can access confined, narrow spaces, inspiring scientists to fabricate soft robots for in vivo manipulation of cells or tissues and minimally invasive surgery. We report a super‐soft and super‐elastic magnetic DNA hydrogel‐based soft robot (DNA robot), which presents a shape‐adaptive property and enables magnetically driven navigational locomotion in confined and unstructured space. The DNA hydrogel is designed with a combinational dynamic and permanent crosslinking network through chain entanglement and DNA hybridization, resulting in shear‐thinning and cyclic strain properties. DNA robot completes a series of complex magnetically driven navigational locomotion such as passing through narrow channels and pipes, entering grooves and itinerating in a maze by adapting and recovering its shape. DNA robot successfully works as a vehicle to deliver cells in confined space by virtue of the 3D porous networked structure and great biocompatibility. [ABSTRACT FROM AUTHOR]

Spinal cord injury (SCI) is a serious trauma, which often results in a permanent loss of motor and sensory functions, pain and spasticity. Despite extensive research, there is currently no available therapy that would restore the lost functions after SCI in human patients. Advanced treatments use regenerative medicine or its combination with various interdisciplinary approaches such as tissue engineering or biophysical methods. This review summarizes and critically discusses the research from specific interdisciplinary fields in SCI treatment such as the development of biomaterials as scaffolds for tissue repair, and using a magnetic field for targeted cell delivery. We compare the treatment effects of synthetic non-degradable methacrylate-based hydrogels and biodegradable biological scaffolds based on extracellular matrix. The systems using magnetic fields for magnetically guided delivery of stem cells loaded with magnetic nanoparticles into the lesion site are then suggested and discussed. [ABSTRACT FROM AUTHOR]

Magnetically guided cell delivery systems would be valuable to achieve effective macrophage-based cell therapy for colonic inflammatory diseases. In the current study, we developed a method for the efficient and simultaneous introduction of superparamagnetic iron oxide nanoparticles (SPIONs) and plasmid DNA (pDNA) into RAW264 murine macrophage-like cells using SPION-incorporated cationic liposome/pDNA complexes (magnetic lipoplexes). SPIONs and pDNA were introduced for magnetization and functionalization of the macrophages, respectively. We also evaluated the adhesive properties of magnetized RAW264 cells using magnetic lipoplexes in the murine colon under a magnetic field. Significant cellular association and gene expression without cytotoxicity were observed when magnetic cationic liposomes and pDNA were mixed at a weight ratio of 10:1, and SPION concentration and magnetic field exposure time was 0.1 mg/mL and 10 min, respectively. We also observed that cytokine production in magnetized RAW264 cells was similar to that in non-treated RAW264 cells, whereas nitric oxide production was significantly increased in magnetized RAW264 cells. Furthermore, magnetized RAW264 cells highly adhered to a Caco-2 cell monolayer and colon in mice, under a magnetic field. These results suggest that this magnetic cell delivery system can improve the colonic delivery of macrophages and its therapeutic efficacy against colonic inflammatory diseases. [ABSTRACT FROM AUTHOR]

The present study delineates the preparation, characterization, and application of (3-Aminopropyl)triethoxysilane (APTES)/Caprine liver-derived extracellular matrix (CLECM) coated paper matrix for cell delivery. Here, we exploited positively charged surface of the paper matrix (as imparted by APTES derivatization) to improve the biological responses of the cells. Our results demonstrated that the functionalized paper matrixes favored the adhesion, growth, and proliferation of multiple cell types including normal, transformed, cancerous, and stem cells as compared to the pristine paper matrix. Upon implantation into the mice model, the developed paper matrix supported infiltration of the host cells and vasculature without showing any evidence of significant systemic toxicity. Moreover, the cells cultured on the paper matrix, when delivered to the CAM and mouse models, showed an enhanced vascular network around the substrate, thereby confirming its potential to deliver the cells in vivo. Together, the study confirms that the reported paper-based platform is easy to fabricate, cheap, portable and could efficiently be applied to cell delivery applications for either tissue repair or the development of humanized animal model. • Paper matrix was amino-functionalized using APTES (AF) and coated with CLECM (CAF) • AF matrix supported higher protein adsorption and cell adhesion than untreated group. • CAF matrix supported long-term viability and functionality of HepG2 cells. • CAF matrix successfully delivered the cells in vivo marked by intense angiogenic network. [ABSTRACT FROM AUTHOR]

To fully exploit the potential of hydrogel micro-fibers in the design of regenerative medicinal materials, we designed a simple, easy to replicate system for cell embedding in degradable fibrous scaffolds, and validated its effectiveness using alginate-based materials. For scaffold fabrication, cells are suspended in a hydrogel-precursor and injected in a closed-loop circuit, where a pump circulates the ionic cross-linking solution. The flow of the cross-linking solution stretches and solidifies a continuous micro-scaled, cell-loaded hydrogel fiber that whips, bends, and spontaneously assembles in a self-standing, spaghetti-like patch. After investigation and tuning of process- and solution-related parameters, homogeneous microfibers with controlled diameters and consistent scaffolds were obtained from different alginate concentrations and blends with biologically favorable macromolecules (i.e., gelatin or hyaluronic acid). Despite its simplicity, this coaxial-flow encapsulation system allows for the rapid and effortless fabrication of thick, well-defined scaffolds, with viable cells being homogeneously distributed within the fibers. The reduced fiber diameter and the inherent macro-porous structure that is created from the random winding of fibers can sustain mass transport, and support encapsulated cell survival. As different materials and formulations can be processed to easily create homogeneously cell-populated structures, this system appears as a valuable platform, not only for regenerative medicine, but also, more in general, for 3D cell culturing in vitro. [ABSTRACT FROM AUTHOR]

• Delivery of biomolecules and cells to the CNS remains a challenge. • Hyaluronan/methylcellulose (HAMC) hydrogel promotes cell survival in vivo. • HAMC is a versatile delivery vehicle for controlled biomolecule delivery directly to CNS tissue. • Efficacy of HAMC can be seen in models of retinal degeneration, stroke, and spinal cord injury. Regenerative medicine strategies rely on exogenous cell transplantation and/or endogenous cell stimulation. Biomaterials can help to increase the regenerative potential of cells and biomolecules by controlling transplanted cell fate and provide a local, sustained release of biomolecules. In this review, we describe the use of a hyaluronan/methylcellulose (HAMC)-based hydrogel as a delivery vehicle to the brain, spinal cord, and retina to promote cellular survival and tissue repair. We discuss various controlled release strategies to prolong the delivery of factors for neuroprotection. The versatility of this hydrogel for a diversity of applications highlights its potential to enhance cell- and biomolecule-based treatment strategies. [ABSTRACT FROM AUTHOR]

Highlights • Natural lipids DAG and PS enhanced cell association of CPP-liposomes to VSMCs and VECs in a cell-type specific manner. • Inclusion of DAG decreased octaarginine-mediated liposome toxicity in VSMCs, while no protective effect was observed in VECs. • Inclusion of DAG or PS did not affect liposome properties including size, homogeneity, or siRNA encapsulation efficiency. Abstract Liposomal delivery systems (LDSs) have been at the forefront of medicinal nanotechnology for over three decades. Increasing LDS association to target cells and cargo delivery is crucial to bolstering overall nanodrug efficacy. Our laboratory aims to develop LDSs for molecular therapeutics aimed at vascular pathology. We have previously established a liposome platform that is an effective delivery system for RNA interference in vascular cell types by using polyethylene glycol (PEG) decorated liposomes bearing an octa-arginine (R8) cell penetrating peptide (CPP). Further tailoring liposome membranes to mimic vascular cell membrane lipid constituents may be a promising strategy for increasing cargo delivery. Here we aimed to develop liposomal formulations that could make use of diacylglycerol (DAG) and phosphatidylserine (PS), naturally occurring lipid species that are known to influence vascular cell function, as a facile and efficient means to increase nanodrug efficacy without compromising clinical viability. We investigated the ability of DAG and PS to amplify the cellular uptake of our previously established LDS platform loaded with small interfering ribonucleic acid (siRNA) cargo. Cellular fluorescence microscopy experiments were performed in conjunction with quantitative cell association assays and cytotoxicity assays to analyze the effect of DAG/PS on the differential delivery of fluorescently-tagged liposomes to vascular smooth muscle cells (VSMCs) and vascular endothelial cells (VECs) and on liposomal-mediated toxicity. In these studies, significant, dose-dependent increases in association to target cells were observed, as well as cell-type specific effects on cell viability. The stability and encapsulation-efficiency of the DAG/PS-modified LDSs were analyzed by standard nanoparticle characterization methods, and siRNA transfection efficacy was quantified to gauge delivery potential as a function of DAG/PS modification. Our results suggest that the signaling lipids tested here imbue our LDS architectures with increased therapeutic potential, without compromising stability, encapsulation efficiency, or biocompatibility, thus presenting a natural strategy to increase nanodrug efficacy and specificity. [ABSTRACT FROM AUTHOR]

Abstract The design of tissue engineered scaffolds based on polymerized high internal phase emulsions (polyHIPEs) has emerged as a promising bone grafting strategy. We previously reported the ability to 3D print emulsion inks to better mimic the structure and mechanical properties of native bone while precisely matching defect geometry. In the current study, redox-initiated hydrogel carriers were investigated for in situ delivery of human mesenchymal stem cells (hMSCs) utilizing the biodegradable macromer, poly(ethylene glycol)-dithiothreitol. Hydrogel carrier properties including network formation time, sol-gel fraction, and swelling ratio were modulated to achieve rapid cure without external stimuli and a target cell-release period of 5–7 days. These in situ carriers enabled improved distribution of hMSCs in 3D printed polyHIPE grafts over standard suspension seeding. Additionally, carrier-loaded polyHIPEs supported sustained cell viability and osteogenic differentiation of hMSCs post-release. In summary, these findings demonstrate the potential of this in situ curing hydrogel carrier to enhance the cell distribution and retention of hMSCs in bone grafts. Although initially focused on improving bone regeneration, the ability to encapsulate cells in a hydrogel carrier without relying on external stimuli that can be attenuated in large grafts or tissues is expected to have a wide range of applications in tissue engineering. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Transplantation of progenitor cells can accelerate tissue healing and regenerative processes. Nonetheless, direct cell delivery fails to support survival of transplanted cells or long-term treatment of vascular related diseases due to compromised vasculature and tissue conditions. Using injectable hydrogels that cross-link in situ, could protect cells in vivo , but their sol-gel transition is time-dependent and difficult to precisely control. Hydrogels with self-healing properties are proposed to address these limitations, yet current self-healing hydrogels lack bio-functionality, hindering the morphogenesis of delivered cells into a tissue structure. Here we establish a gelatin (Gtn)-based self-healing hydrogel cross-linked by oxidized dextran (Odex) as an injectable carrier for delivery of endothelial progenitors. The dynamic imine cross-links between Gtn and Odex confer the self-healing ability to the Gtn-l-Odex hydrogels following syringe injection. The self-healing Gtn-l-Odex not only protects the progenitors from injected shear force but it also allows controllable spatial/temporal placement of the cells. Moreover, owing to the cell-adhesive and proteolytic sites of Gtn, the Gtn-l-Odex hydrogels support complex vascular network formation from the endothelial progenitors, both in vitro and in vivo. This is the first report of injectable, self-healing hydrogels with biological properties promoting vascular morphogenesis, which holds great promise for accelerating the success of regenerative therapies. [ABSTRACT FROM AUTHOR]

Carrageenan is a class of naturally occurring sulphated polysaccharides, which is currently a promising candidate in tissue engineering and regenerative medicine as it resemblances native glycosaminoglycans. From pharmaceutical drug formulations to tissue engineered scaffolds, carrageenan has broad range of applications. Here we provide an overview of developing various forms of carrageenan based hydrogels. We focus on how these fabrication processes has an effect on physiochemical properties of the hydrogel. We outline the application of these hydrogels not only pertaining to sustained drug release but also their application in bone and cartilage tissue engineering as well as in wound healing and antimicrobial formulations. Administration of these hydrogels through various routes for drug delivery applications has been critically reviewed. Finally, we conclude by summarizing the current and future outlook that promotes the seaweed-derived polysaccharide as versatile, promising biomaterial for a variety of bioengineering applications. [ABSTRACT FROM AUTHOR]

The objective of this study was to design an injectable biomaterial system that becomes porous in situ to deliver and control vascular progenitor cell release. Alginate hydrogels were loaded with outgrowth endothelial cells (OECs) and alginate lyase, an enzyme which cleaves alginate polymer chains. We postulated and confirmed that higher alginate lyase concentrations mediated loss of hydrogel mechanical properties. Hydrogels incorporating 5 and 50 mU/mL of alginate lyase experienced approximately 28% and 57% loss of mass as well as 81% and 91% reduction in storage modulus respectively after a week. Additionally, computational methods and mechanical analysis revealed that hydrogels with alginate lyase significantly increased in mesh size over time. Furthermore, alginate lyase was not found to inhibit OEC proliferation, viability or sprouting potential. Finally, alginate hydrogels incorporating OECs and alginate lyase promoted up to nearly a 10 fold increase in OEC migration in vitro than nondegradable hydrogels over the course of a week and increased functional vasculature in vivo via a chick chorioallantoic membrane (CAM) assay. Overall, these findings demonstrate that alginate lyase incorporated hydrogels can provide a simple and robust system to promote controlled outward cell migration into native tissue for potential therapeutic revascularization applications. [ABSTRACT FROM AUTHOR]

Cell-hydrogel based therapies offer great promise for wound healing. The specific aim of this study was to assess the viability of human hepatocellular carcinoma (HepG2) cells immobilized in atomized alginate capsules (3.5% (w/v) alginate, d = 225 μm ± 24.5 μm) post-extrusion through a three-dimensional (3D) printed methacrylate-based custom hollow microneedle assembly (circular array of 13 conical frusta) fabricated using stereolithography. With a jetting reliability of 80%, the solvent-sterilized device with a root mean square roughness of 158 nm at the extrusion nozzle tip (d = 325 μm) was operated at a flowrate of 12 mL/min. There was no significant difference between the viability of the sheared and control samples for extrusion times of 2 h (p = 0.14, a = 0.05) and 24 h (p = 0.5, a = 0.05) post-atomization. Factoring the increase in extrusion yield from 21.2% to 56.4% attributed to hydrogel bioerosion quantifiable by a loss in resilience from 5470 (J/m3) to 3250 (J/m3), there was no significant difference in percentage relative payload (p = 0.2628, a = 0.05) when extrusion occurred 24 h (12.2 ± 4.9%) when compared to 2 h (9.9 ± 2.8%) post-atomization. Results from this paper highlight the feasibility of encapsulated cell extrusion, specifically protection from shear, through a hollow microneedle assembly reported for the first time in literature. [ABSTRACT FROM AUTHOR]

A covalently cross-linked injectable hybrid hydrogel, namely, alginate/poly(amidoamine) (PAMAM), with the objective of cell delivery was innovatively designed and synthesized using tetra-amino-functional PAMAM dendrimer as the cross-linker. With the increase in percentage of PAMAM cross-linker, the pore size and swelling ratio of hydrogels were in the range of 57 ± 18 μm to 88 ± 25 μm and 110 ± 16 to 157 ± 20, respectively. The study of attachment and proliferation of MC3T3-E1 pre-osteoblasts using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay through indirect and direct contact methods indicated a continuous increase in metabolically active live cells with time, implying non-cytotoxicity of the synthesized hydrogel. The live–dead assay showed >95% of live cells for alginate/PAMAM hydrogels, suggesting viability of the encapsulated cells. When the percentage of PAMAM cross-linker in alginate/PAMAM hydrogel was increased from 5 to 25, the percentage degradation rate decreased from 1.1 to 0.29%/day. Given that the poly(ethylene glycol) is commonly used cross-linker for hydrogel syntheses, we compared the behavior with poly(ethylene glycol). The incorporation of poly(ethylene glycol) in alginate/PAMAM hydrogel reduced the activity of MC3T3-E1 cells and their viability compared to the alginate/PAMAM hydrogels. The protonation of amino groups in alginate/PAMAM injectables under physiological conditions led to the formation of cationic hydrogels. These cationic hydrogels showed enhanced cell encapsulation and attachment ability because of electrostatic interaction with negatively charged cell surface as determined by cell adhesion and extensions from scanning electron microscope and vinculin assay and ability of in situ calcium phosphate mineralization. These observations point toward the potential use as an injectable scaffold for cell delivery and tissue engineering applications. [ABSTRACT FROM AUTHOR]

Injectable hydrogels, which are used as scaffolds in cell therapy, provide a minimally invasive strategy to enhance cell retention and survival at injection site. However, till now, slow in situ gelation, undesired mechanical properties, and weak cell adhesion characteristics of reported hydrogels, have led to improper results. Here, we developed an injectable fully-interpenetrated polymer network (f-IPN) by integration of Diels-Alder (DA) crosslinked network and thermosensitive injectable hydrogel. The proposed DA hydrogels were formed in a slow manner showing robust mechanical properties. Interpenetration of thermosensitive network into DA hydrogel accelerated in situ gel-formation and masked the slow reaction rate of DA crosslinking while keeping its unique features. Two networks were formed by simple syringe injection without the need of any initiator, catalyst, or double barrel syringe. The DA and f-IPN hydrogels showed comparable viscoelastic properties along with outstanding load-bearing and shape-recovery even under high levels of compression. The subcutaneous administration of cardiomyocytes-laden f-IPN hydrogel into nude mice revealed high cell retention and survival after two weeks. Additionally, the cardiomyocyte's identity of retained cells was confirmed by detection of human and cardiac-related markers. Our results indicate that the thermosensitive-covalent networks can open a new horizon within the injection-based cell therapy applications. [ABSTRACT FROM AUTHOR]

A micropatterned heparin-based hydrogel system that can provide sustained release of multiple growth factors upon one time loading was prepared via photopolymerization and lithography and it was employed as a culture matrix for differentiating hADSCs into hepatic lineage. Mature differentiation of hADSCs into hepatic lineage in terms of gene expression and immunofluorostaining of hepatic markers, and functional characteristics such as glycogen storage ability and production of albumin and urea was observed on the soft hydrogel (∼400 Pa) when the gel elasticity was modulated. This optimal heparin-based hydrogel was used to prepare micropatches containing hepatic-differentiated cells by 1) micropatterning of the gel on a polyelectrolyte multilayer (PEM), 2) seeding of hADSCs and inducing hepatic differentiation, and 3) electrochemical retrieval of cell-attached micropatches. Upon i.v. injection, the retrieved cell micropatches showed a prolonged retention in the liver and promoted function compared to single cell injection in a rat model. In conclusion, this injectable and detachable miropatterned heparin-based hydrogel system could serve as a total platform for the stem cell differentiation under well-controlled microenvironment in vitro and for targeted delivery of the differentiated cells in vivo . [ABSTRACT FROM AUTHOR]

Abstract: Live‐cell labeling, super‐resolution microscopy, single‐molecule applications, protein localization, or chemically induced assembly are emerging approaches, which require specific and very small interaction pairs. The minimal disturbance of protein function is essential to derive unbiased insights into cellular processes. Herein, we define a new class of hexavalent N‐nitrilotriacetic acid (hexaNTA) chelators, displaying the highest affinity and stability of all NTA‐based small interaction pairs described so far. Coupled to bright organic fluorophores with fine‐tuned photophysical properties, the super‐chelator probes were delivered into human cells by chemically gated nanopores. These super‐chelators permit kinetic profiling, multiplexed labeling of His6‐ and His12‐tagged proteins as well as single‐molecule‐based super‐resolution imaging. [ABSTRACT FROM AUTHOR]

Corneal blindness is a worldwide problem, plagued by insufficient amount of high-quality donor tissue. Cell therapy using human adipose stem cells (hASCs) has risen as an alternative to regenerate damaged corneal stromal tissue, the main structural and refractive layer of the cornea. Herein we propose a method to deliver hASCs into corneal defects in hyaluronan (HA)-based hydrogels, which form rapidly in situ by hydrazone crosslinking. We fabricated two different HA-based hydrazone-crosslinked hydrogels (HALD1-HACDH and HALD2-HAADH), and characterized their swelling, degradation, mechanical, rheological and optical properties and their ability to support hASC survival. To promote hASC attachment and survival, we incorporated collagen I (col I) to the more stable HALD1-HACDH hydrogel, since the HALD2-HAADH hydrogel suffered swift degradation in culture conditions. We then used an organ culture model with excised porcine corneas to study the delivery of hASCs in these three hydrogels for stromal defect repair. Although all hydrogels showed good hASC survival directly after encapsulation, only the collagen-containing HALD1-HACDH-col I hydrogel showed cells with elongated morphology, and significantly higher cell metabolic activity than the HALD1-HACDH gel. The addition of col I also increased the stiffness and reduced the swelling ratio of the resulting hydrogel. Most importantly, the corneal organ culture model demonstrated these hydrogels as clinically feasible cell delivery vehicles to corneal defects, allowing efficient hASC integration to the corneal stroma and overgrowth of corneal epithelial cells. [ABSTRACT FROM AUTHOR]