Search

As a biodegradable and biocompatible protein derived from collagen, gelatin has been extensively exploited as a fundamental component of biological scaffolds and drug delivery systems for precise medicine. The easily engineered gelatin holds great promise in formulating various delivery systems to protect and enhance the efficacy of drugs for improving the safety and effectiveness of numerous pharmaceuticals. The remarkable biocompatibility and adjustable mechanical properties of gelatin permit the construction of active 3D scaffolds to accelerate the regeneration of injured tissues and organs. In this Review, we delve into diverse strategies for fabricating and functionalizing gelatin-based structures, which are applicable to gene and drug delivery as well as tissue engineering. We emphasized the advantages of various gelatin derivatives, including methacryloyl gelatin, polyethylene glycol-modified gelatin, thiolated gelatin, and alendronate-modified gelatin. These derivatives exhibit excellent physicochemical and biological properties, allowing the fabrication of tailor-made structures for biomedical applications. Additionally, we explored the latest developments in the modulation of their physicochemical properties by combining additive materials and manufacturing platforms, outlining the design of multifunctional gelatin-based micro-, nano-, and macrostructures. While discussing the current limitations, we also addressed the challenges that need to be overcome for clinical translation, including high manufacturing costs, limited application scenarios, and potential immunogenicity. This Review provides insight into how the structural and chemical engineering of gelatin can be leveraged to pave the way for significant advancements in biomedical applications and the improvement of patient outcomes.

Amorphous iron-calcium phosphate (Fe-ACP) plays a vital role in the mechanical properties of teeth of some rodents, which are very hard, but its formation process and synthetic route remain unknown. Here, the synthesis and characterization of an iron-bearing amorphous calcium phosphate in the presence of ammonium iron citrate (AIC) are reported. The iron is distributed homogeneously on the nanometer scale in the resulting particles. The prepared Fe-ACP particles can be highly stable in aqueous media, including water, simulated body fluid, and acetate buffer solution (pH 4). In vitro study demonstrates that these particles have good biocompatibility and osteogenic properties. Subsequently, Spark Plasma Sintering (SPS) is utilized to consolidate the initial Fe-ACP powders. The results show that the hardness of the ceramics increases with the increase of iron content, but an excess of iron leads to a rapid decline in hardness. Calcium iron phosphate ceramics with a hardness of 4 GPa can be achieved, which is higher than that of human enamel. Furthermore, the ceramics composed of iron-calcium phosphates show enhanced acid resistance. This study provides a novel route to prepare Fe-ACP, and presents the potential role of Fe-ACP in biomineralization and as starting material to fabricate acid-resistant high-performance bioceramics.

Introduction: The conventional treatment for irreversibly inflamed or necrotic teeth is root canal treatment or apexification. Regenerative endodontics aims to regenerate the damaged “pulp-like” tissue, which can preserve the teeth' vitality and sensitivity while avoiding necrosis. The main clinical benefit is root maturation. The “pulp-like” tissue does not refer to regenerated pulp tissue with an odontoblastic layer or the formation of pulp-dentin complexes. The cell homing technique is built on endogenous stem cells and their capacity to regenerate tissue. Cell homing refers to endogenous cells’ migration or infiltration into the cite when stimulated by physiochemical or biological stimuli or by passive flow with a blood clot from the apical tissue. Its Regenerative Endodontic Procedures success criteria are defined by the American Association of Endodontists. The purpose of this article is to provide an overview of vital pulp tissue and various strategies to promote regeneration of damaged pulp tissue. The cell homing technique will be reviewed through clinical trials. Methods: We performed a comprehensive literature review on a total of nine clinical trials of regenerative endodontics using the cell-homing technique based on three databases and duplicate manuscripts were removed. Results: Regenerative endodontics using the cell-homing technique shows promising results that can be translated into clinical practice. However, a favorable result was observed in immature teeth, and the results are contradictory in mature teeth. Conclusion: Regeneration therapy is an attractive new alternative to conventional endodontic treatments. Preservation of vitality and continuation of root development in damaged teeth would be a clear advantage., QC 20230615

Mucus is a self-healing gel that lubricates the moist epithelium and provides protection against viruses by binding to viruses smaller than the gel’s mesh size and removing them from the mucosal surface by active mucus turnover. As the primary nonaqueous components of mucus (≈0.2%–5%, wt/v), mucins are critical to this function because the dense arrangement of mucin glycans allows multivalence of binding. Following nature’s example, bovine submaxillary mucins (BSMs) are assembled into “mucus-like” gels (5%, wt/v) by dynamic covalent crosslinking reactions. The gels exhibit transient liquefaction under high shear strain and immediate self-healing behavior. This study shows that these material properties are essential to provide lubricity. The gels efficiently reduce human immunodeficiency virus type 1 (HIV-1) and genital herpes virus type 2 (HSV-2) infectivity for various types of cells. In contrast, simple mucin solutions, which lack the structural makeup, inhibit HIV-1 significantly less and do not inhibit HSV-2. Mechanistically, the prophylaxis of HIV-1 infection by BSM gels is found to be that the gels trap HIV-1 by binding to the envelope glycoprotein gp120 and suppress cytokine production during viral exposure. Therefore, the authors believe the gels are promising for further development as personal lubricants that can limit viral transmission., QC 20221216

Hydrogel biomaterials have found use in various biomedical applications partly due to their biocompatibility and tuneable viscoelastic properties. The ideal rheological properties of hydrogels depend highly on the application and should be considered early in the design process. Rheometry is the most common method to study the viscoelastic properties of hydrogels. However, rheometers occupy much space and are costly instruments. On the other hand, quartz crystal resonators (QCRs) are devices that can be used as low-cost, small, and accurate sensors to measure the viscoelastic properties of fluids. For this reason, we explore the capabilities of a low-cost and compact QCR sensor to sense and characterise the gelation process of hydrogels while using a low sample amount and by sensing two different crosslink reactions: covalent bonds and divalent ions. The gelation of covalently crosslinked mucin hydrogels and physically crosslinked alginate hydrogels could be monitored using the sensor, clearly distinguishing the effect of several parameters affecting the viscoelastic properties of hydrogels, including crosslinking chemistry, polymer concentrations, and crosslinker concentrations. QCR sensors offer an economical and portable alternative method to characterise changes in a hydrogel material's viscous properties to contribute to this type of material design, thus providing a novel approach., QC 20221206

Osteoclast (OC) abnormalities represent osteoporosis's critical mechanism (OP). OCs undergo multiple processes that range from monocytic to functional. Different drugs target OCs at different developmental stages; however, almost no Suitable drug-targeted delivery systems exist. Therefore, we designed two dual-targeting nanoparticles to target OCs at different functional stages. Using the calcitonin gene-related peptide receptor (CGRPR), which OC precursors highly express, and specific TRAPpeptides screened in the bone resorption lacuna, where mature OCs function, respectively, two types of dual-targeted nanoparticles were constructed. Afterwards, nanoparticles were grafted with hyaluronic acid (HA), which specifically binds to CD44 on the surface of the OCs. In vivo and in vitro experiments show that both nanoparticles have noticeable targeting effects on OCs. This suggests that dual-targeting nanoparticles designed for different functional periods of OC can be well targeted to the corresponding OC, and further promote the more precise delivery of drugs used to treat OP., QC 20221214

Mitochondrial damage is one of the primary causes of neuronal cell death in Parkinson's disease (PD). In PD patients, the mitochondrial damage can be repaired or irreversible. Therefore, mitochondrial damage repair becomes a promising strategy for PD treatment. In this research, hyaluronic acid nanoparticles (HA-NPs) of different molecular weights are used to protect the mitochondria and salvage the mild and limited damage in mitochondria. The HA-NPs with 2190 k Dalton (kDa) HA can improve the mitochondrial function of SH-SY5Y cells and PTEN induced putative kinase 1 (PINK1) knockout mouse embryo fibroblast (MEF) cells. In cases of irreversible damage, NPs with ubiquitin specific peptidase 30 (USP30) siRNA are used to promote mitophagy. Meanwhile, by adding PINK1 antibodies, the NPs can selectively target the irreversibly damaged mitochondria, preventing the excessive clearance of healthy mitochondria., QC 20220706

Immune-modulating biomaterials used to encapsulate cells and microtissue transplants can be engineered to dampen the immune reaction and increase treatment efficacy. Mucin-derived materials have gained attention for their ability to modulate macrophage and dendritic cell activity, and to trigger mild foreign body response when implanted in vivo. In this study, the potential of mucin hydrogels (Muc-gels) as cell-encapsulating materials is investigated. When placed in contact with blood, Muc-gels trigger significantly lower complement activation, compared to clinical grade alginate hydrogels. Muc-gel is a size-selective barrier strongly hindering the diffusion of molecules with a hydrodynamic radius larger than 6 nm such as immunoglobulins. Muc-gels support the growth of MIN6m9 insulin-secreting cells into islet-like organoids and the survival of primary human pancreatic islets, which maintained glucose responsiveness. Muc-gels can be shaped into microdroplets in which MIN6m9 cells or cell aggregates can be encapsulated without loss of viability. Microdroplet encapsulation will allow transplants to be easily injected and improve their survival by favoring mass transport through the capsule. The combination of strong immune modulatory properties, appropriate selective barrier profile, biocompatibility for embedded cells Muc-gels of particular value for microencapsulating cells or microtissues for transplantation.

Hydrogels made of crosslinked macromolecules used in regenerative medicine technologies can be designed to affect the fate of surrounding cells and tissues in defined ways. Their function typically depends on the type and number of bioactive moieties such as receptor ligands present in the hydrogel. However, the detail in how such moieties are presented to cells can also be instrumental. In this work, how the crosslinking architecture of a hydrogel can affect its bioactivity is explored. It is shown that bovine submaxillary mucins, a highly glycosylated and immune-modulating protein, exhibit strikingly different bioactivities whether they are crosslinked through their glycans or their protein domains. Both the susceptibility to enzymatic degradation and macrophage response are affected, while rheological properties and barrier to diffusion are mostly unaffected. The results suggest that crosslinking architecture affects the accessibility of the substrate to proteases and the pattern of sialic acid residues exposed to the macrophages. Thus, modulating the accessibility of binding sites through the choice of the crosslinking strategy appears as a useful parameter to tune the bioactivity of hydrogel-based systems., QC 20211110

In vitro cancer models that can largely mimic the in vivo microenvironment are crucial for conducting more accurate research. Models of three-dimensional (3D) culture that can mimic some aspects of cancer microenvironment or cancer biopsies that can adequately represent tumor heterogeneity are intensely used currently. Those models still lack the dynamic stress stimuli in gastric carcinoma exposed to stomach peristalsis in vivo. This study leveraged a lab-developed four-dimensional (4D) culture model by a magnetic responsive alginate-based hydrogel to rotating magnets that can mimic stress stimuli in gastric cancer (GC). We used the 4D model to culture human GC cell line AGS and SGC7901, cells at the primary and metastasis stage. We revealed the 4D model altered the cancer cell growth kinetics mechanistically by altering PCNA and p53 expression compared to the 3D culture that lacks stress stimuli. We found the 4D model altered the cancer spheroids stemness as evidenced by enhanced cancer stem cells (CD44) marker expression in AGS spheroids but the expression was dampened in SGC7901 cells. We examined the multi-drug resistance (MDR1) marker expression and found the 4D model dampened the MDR1 expression in SGC7901 cell spheroids, but not in spheroids of AGS cells. Such a model provides the stomach peristalsis mimic and is promising for conducting basic or translational GC-associated research, drug screening, and culturing patient gastric biopsies to tailor the therapeutic strategies in precision medicine., QC 20210524

Cancer stem cells (CSCs) are self-renewing and constitute the primary cause of cancer relapse post-cancer therapy. The CSC niche is composed of various nonmalignant stromal cells that support CSCs' survival during cancer chemoradiotherapy. Understanding the cross-talk between CSCs and stromal cells could pave the way for developing therapeutic strategies to eradicate CSCs. Traditionally, CSC research has been relying on animal models, which can give rise to complications and poor translation in clinical practice. An efficient model to co-culture CSCs and stromal cells is urgently needed. Hence, we leveraged our expertise in enriching CSCs from in vitro cell lines with a 3D alginate-based platform, as reported previously. We established a 3D co-culture system that allowed us to study the interactions between stromal cells and CSCs over an extended period. We showed that the self-renewal capacity and stemness of CSCs were significantly enhanced when co-cultured with 3D cultured human umbilical vein endothelial cells (HUVECs) or a human monocyte cell line (THP1). Strikingly, the expression of MDR1 in 3D co-cultured CSCs was upregulated, leading to enhanced chemotoxic drug tolerance. We suggest that our in vitro co-culture model can impact CSC research and clinical practice when the goal is to develop therapeutics that target and eradicate CSCs by targeting stromal cells., QC 20210525

Gaining control over the delivery of therapeutics to a specific disease site is still very challenging. However, especially when cytotoxic drugs such as chemotherapeutics are used, the importance of a control mechanism that can differentiate "sick" target cells from the surrounding healthy tissue is pivotal. Here, we designed a nanoparticle-based drug delivery process, which releases an active agent only in the presence of a specific trigger DNA sequence. With this strategy, we are able to initiate the release of therapeutics into the cytosol with high efficiency. Furthermore, we demonstrate how an endogenous marker (e.g., a specific miRNA sequence) that is overexpressed in the initial phases of certain cancer types can be used as a stimulus to autonomously initiate intracellular drug release-and only in cells where this pathophysiological marker is present. We expect that this precisely controlled delivery mechanism can facilitate the design of site-specific treatments for such diseases, where an overexpression of signature oligonucleotide sequences has been identified., QC 20210415

Mucins are multifunctional glycosylated proteins that are increasingly investigated as building blocks of novel biomaterials. An attractive feature is their ability to modulate the immune response, in part by engaging with sialic acid binding receptors on immune cells. Once assembled into hydrogels, bovine submaxillary mucins (Muc gels) were shown to modulate the recruitment and activation of immune cells and avoid fibrous encapsulation in vivo. However, nothing is known about the early immune response to Muc gels. This study characterizes the response of macrophages, important orchestrators of the material-mediated immune response, over the first 7 days in contact with Muc gels. The role of mucin-bound sialic acid sugar residues was investigated by first enzymatically cleaving the sugar and then assembling the mucin variants into covalently cross-linked hydrogels with rheological and surface nanomechanical properties similar to nonmodified Muc gels. Results with THP-1 and human primary peripheral blood monocytes derived macrophages showed that Muc gels transiently activate the expression of both pro-inflammatory and anti-inflammatory cytokines and cell surface markers, for most makers with a maximum on the first day and loss of the effect after 7 days. The activation was sialic acid-dependent for a majority of the markers followed. The pattern of gene expression, protein expression, and functional measurements did not strictly correspond to M1 or M2 macrophage phenotypes. This study highlights the complex early events in macrophage activation in contact with mucin materials and the importance of sialic acid residues in such a response. The enzymatic glyco-modulation of Muc gels appears as a useful tool to help understand the biological functions of specific glycans on mucins which can further inform on their use in various biomedical applications., QC 20200714

The immune-mediated foreign body response to biomaterial implants can trigger the formation of insulating fibrotic capsules that can compromise implant function. To address this challenge, the intrinsic bioactivity of the mucin biopolymer, a heavily glycosylated protein that forms the protective mucus gel covering mucosal epithelia, is leveraged. By using a bioorthogonal inverse electron demand Diels-Alder reaction, mucins are crosslinked into implantable hydrogels. It is shown that mucin hydrogels (Muc-gels) modulate the immune response driving biomaterial-induced fibrosis. Muc-gels do not elicit fibrosis 21 days after implantation in the peritoneal cavity of C57Bl/6 mice, whereas medical-grade alginate hydrogels are covered by fibrous tissues. Further, Muc-gels dampen the recruitment of innate and adaptive immune cells to the gel and trigger a pattern of very mild activation marked by a noticeably low expression of the fibrosis-stimulating transforming growth factor beta 1 cytokine. Macrophages recruited to Muc-gels upregulate the gene expression of the protein inhibitor of activated STAT 1 (PIAS1) and SH2-containing phosphatase 1 (SHP-1) cytokine regulatory proteins, which likely contributes to their low cytokine expression profiles. With this advance in mucin materials, an essential tool is provided to better understand mucin bioactivities and to initiate the development of new mucin-based and mucin-inspired "immune-informed" materials for implantable devices subject to fibrotic encapsulation.

The many interesting properties of chitosan polysaccharides have prompted their extensive use as biomaterial building blocks, for instance as antimicrobial coatings, tissue engineering scaffolds, and drug delivery vehicles. The translation of these chitosan-based systems to the clinic still requires a deeper understanding of their safety profiles. For instance, the widespread claim that chitosans are spermicidal is supported by little to no data. Herein, we thoroughly investigate whether chitosan oligomer (CO) molecules can impact the functional and structural features of human spermatozoa. By using a large number of primary sperm cell samples and by isolating the effect of chitosan from the effect of sperm dissolution buffer, we provide the first realistic and complete picture of the effect of chitosans on sperms. We found that CO binds to cell surfaces or/and is internalized by cells and affected the average path velocity of the spermatozoa, in a dose-dependent manner. However, CO did not affect the progressive motility, motility, or sperm morphology, nor did it cause loss of plasma membrane integrity, reactive oxygen species production, or DNA damage. A decrease in spermatozoa adenosine triphosphate levels, which was especially significant at higher CO concentrations, points to possible interference of CO with mitochondrial functions or the glycolysis processes. With this first complete and in-depth look at the spermicidal activities of chitosans, we complement the complex picture of the safety profile of chitosans and inform on further use of chitosans in biomedical applications., QC 20200205

Synthetic scaffolds that possess an intrinsic capability to protect and sequester sensitive growth factors is a primary requisite for developing successful tissue engineering strategies. Growth factors such as recombinant human bone morphogenetic protein-2 (rhBMP-2) is highly susceptible to premature degradation and to provide a meaningful clinical outcome require high doses that can cause serious side effects. We discovered a unique strategy to stabilize and sequester rhBMP-2 by enhancing its molecular interactions with hyaluronic acid (HA), an extracellular matrix (ECM) component. We found that by tuning the initial protonation state of carboxylic acid residues of HA in a covalently crosslinked hydrogel modulate BMP-2 release at physiological pH by minimizing the electrostatic repulsion and maximizing the Van der Waals interactions. At neutral pH, BMP-2 release is primarily governed by Fickian diffusion, whereas at acidic pH both diffusion and electrostatic interactions between HA and BMP-2 become important as confirmed by molecular dynamics simulations. Our results were also validated in an in vivo rat ectopic model with rhBMP-2 loaded hydrogels, which demonstrated superior bone formation with acidic hydrogel as compared to the neutral counterpart. We believe this study provides new insight on growth factor stabilization and highlights the therapeutic potential of engineered matrices for rhBMP-2 delivery and may help to curtail the adverse side effects associated with the high dose of the growth factor., De två första författarna delar förstaförfattarskapet.

Mucins are high molar mass glycoproteins that assume an extended conformation and can assemble into mucus hydrogels that protect our mucosal epithelium. In nature, the challenging task of generating a mucus layer, several hundreds of micrometers in thickness, from micrometer-sized cells is elegantly solved by the condensation of mucins inside vesicles and their on-demand release from the cells where they suddenly expand to form the extracellular mucus hydrogel. We aimed to recreate and control the process of compaction for mucins, the first step toward a better understanding of the process and creating biomimetic in vivo delivery strategies of macromolecules. We found that by adding glycerol to the aqueous solvent, we could induce drastic condensation of purified mucin molecules, reducing their size by an order of magnitude down to tens of nanometers in diameter. The condensation effect of glycerol was fully reversible and could be further enhanced and partially stabilized by cationic cross-linkers such as calcium and polylysine. The change of structure of mucins from extended molecules to nano-sized particles in the presence of glycerol translated into macroscopic rheological changes, as illustrated by a dampened shear-thinning effect with increasing glycerol concentration. This work provides new insight into mucin condensation, which could lead to new delivery strategies mimicking cell release of macromolecules condensed in vesicles such as mucins and heparin., QC 20190109

Embryonic microenvironments can reverse the metastatic phenotype of aggressive tumors by inhibiting the Nodal signaling pathway. Here, we hypothesize that embryonic microenvironments can be transplanted for the purpose of oncotherapy. We report the development of an injectable bioactive hydrogel system containing the key antagonists of Nodal signaling-Cripto-1 receptor antibodies (2B11)-for the creation of embryonic microenvironments and the examination of their effect on tumor reversion treatment using a mouse model. Our in vitro results show that the hydrogel system can reduce the mitochondrial membrane potential of MDA-MB-231 and MCF-7, promote cell apoptosis, and reduce the invasive ability of cells. Our in vivo results illustrate that the hydrogel system can significantly inhibit tumor growth in both breast cancer and melanoma tumor-bearing mouse models, as well as transform the cell morphology of melanoma B16 cells to melanin-like cells. Furthermore, the results of the up-regulation of tumor suppressor genes and the down-regulation of oncogenes by high-throughput sequencing confirm that the developed system can also selectively turn on some tumor suppressor genes and turn off certain oncogenes so as to prompt the benign reversion of the tumor phenotype. Taken together, our results demonstrate the injectable biomaterial system is able to create an effective microenvironment for melanoma and breast tumor therapy.

This thesis presents deeper insights into bone applicable biomaterials’ design. Poor affinity of BMP-2 towards scaffolds required supra-physiological dose administration. Though molecules containing sulfate could sustain BMP-2 release, side effects occurred due to BMP-2 supra-dose, or these sulfate-containing biomolecules. Improved affinity between BMP-2 and scaffolds was first witnessed by using an acidic carrier (paper I). Hyaluronic acid (HA) hydrazone derived hydrogels having a pH of 4.5-loaded BMP-2 showed sustained release of bioactive BMP-2 in vitro and enhanced bone formation in vivo, while pH 7 HA hydrogels showed Fickian behavior and less bone formation in vivo. Computational evaluation revealed stronger electrostatic interactions between BMP-2, and HA were predominant at pH 4.5, whereas, weaker Van der Waals interactions played a key role at pH 7. During the pre-bone formation phase, endogenous cell responses to pH 4.5 and 7 with or without BMP-2 were investigated. HA hydrogels exhibited extraordinary biocompatibility and recruitment of neutrophils, monocytes, macrophages and stromal cells regardless of hydrogels’ pH and BMP-2 presence. The different inflammatory responses to HA hydrogels were observed (Appendix). Thiol derivatives can cleave the disulfide bond of BMP-2 to generate inactive monomeric BMP-2. In paper II, thiol-acrylate chemistry-based HA hydrogels (HA-SH) were compared to hydrazone-based HA hydrogels as BMP-2 carriers. Thiol modified HA disrupted BMP-2 integrity and bioactivity. HA-SH hydrogels with BMP-2 exhibited less bioactive BMP-2 release in vitro and induced less bone formation in vivo. Accumulated evidence has shown great osteogenic potential of lithium ions (Li). In paper III, we coordinated Li onto HA-PVA hydrazone hydrogels (Li-gel); Li-gel enhanced 3D cultured hMSCs osteogenic differentiation and induced higher bone formation in CAM defect model. Instead of BMP-2 protein, delivery of BMP-2-coding-plasmid can produce BMP-2 over

Degradation of plasmid DNA (pDNA) in the endosome compartment and its release to the cytosol are the major hurdles for efficient gene transfection. This is generally addressed by using transfection reagents that can overcome these limitations. In this article, the first report is presented which suggests that controlling the release of pDNA from endosome is the key for achieving efficient transfection. In this study, chondroitin sulfate (CS)-coated DNA-nanoplexes are developed using a modular approach where CS is coated post-pDNA/PEI nanoplex formation. To ensure good stability of the nanoplexes, imine/enamine chemistry is exploited by reacting aldehyde-modified chondroitin sulfate (CS-CHO) with free amines of pDNA/PEI complex. This supramolecular nanocarrier system displays efficient cellular uptake, and controlled endosomal pDNA release without eliciting any cytotoxicity. On the contrary, burst release of pDNA from endosome (using chloroqine) results in significant reduction in gene expression. Unlike pDNA/PEI-based transfection, the nanoparticle design presented here shows exceptional stability and gene transfection efficiency in different cell lines such as human colorectal cancer cells (HCT116), human embryonic kidney cells (HEK293), and mouse skin-derived mesenchymal stem cells (MSCs) using luciferase protein as a reporter gene. This new insight will be valuable in designing next generation of transfection reagents.

Aldehydes have been used as an important bioorthogonal chemical reporter for conjugation of large polymers and bioactive substances. However, generating aldehyde functionality on carbohydrate-based biopolymers without changing its native chemical structure has always persisted as a challenging task. The common methods employed to achieve this require harsh reaction conditions, which often compromise the structural integrity and biological function of these sensitive molecules. Here we report a mild and simple method to graft aldehydes groups on glycosaminoglycans (GAGs) in a site-selective manner without compromising the structural integrity of the biopolymer. This regio-selective modification was achieved by conjugating the amino-glycerol moiety on the carboxylate residue of the polymer, which allowed selective cleavage of pendent diol groups without interfering with the C2C3 diol groups of the native glucopyranose residue. Kinetic evaluation of this reaction demonstrated significant differences in second-order reaction rate for periodate oxidation (by four-orders of magnitude) between the two types of vicinal diols. We employed this chemistry to develop aldehyde modifications of sulfated and nonsulfated GAGs such as hyaluronic acid (HA), heparin (HP), and chondroitin sulfate (CS). We further utilized these aldehyde grafted GAGs to tailor extracellular matrix mimetic injectable hydrogels and evaluated its rheological properties. The composition of the hydrogels was also found to modulate release of therapeutic protein such as FGF-2, demonstrating controlled release (60%) for over 14 days. In short, our result clearly demonstrates a versatile strategy to graft aldehyde groups on sensitive biopolymers under mild conditions that could be applied for various bioconjugation and biomedical applications such as drug delivery and regenerative medicine., De två (2) första författarna delar förstaförfattarskapet.

Site-specific administration of bone morphogenetic protein-2 (BMP-2) at the site of a bone fracture via scaffolds can minimise systemic side-effects and exhibit sustained biological effects. While this method requires sufficient scaffolds to preserve the BMP-2 structure and tuned release patterns, the incorporation of thiol-acrylate chemistry has shown great success in scaffold synthesis. However, thiolates attack the sulphur atoms of disulphide bonds, displacing the other sulphur atom and forming a new disulphide bond, hence at physiological conditions, thiol-modified scaffold components could potentially attack inter-chain disulphide bonds of BMP-2 by thiol-exchange reactions. This therefore led us to compare hyaluronic acid (HA) hydrogels synthesised via thiol-acrylate (HA-S) and hydrazone crosslinking chemistry (HA-H) formed BMP-2 carriers. The study revealed the integrity of BMP-2 dimer structures can be disrupted and reveals the osteogenic capacity of BMP-2 by HA derivatives (HA-SH). BMP-2 bioactivity released from HA-S hydrogels are decreased when compared to HA-H hydrogels. This was further confirmed via the rat ectopic bone model, showing that bone volume was significantly higher when induced by HA-H hydrogels with BMP-2 than compared to HA-S hydrogel with BMP-2. This study gives new insights into scaffolds synthesis, showing that biomolecule bioactivity needs to be considered when choosing a chemistry for scaffolds synthesis.

Lithium is a clinical drug for bipolar disorders and can enhance bone mass, promote osteogenesis of MSCs through inhibiting the Wnt/β-catenin signalling inhibitor GSK 3β. However, the systemic administration of lithium can trigger severe side-effects. Local administration has been attempted in the treatment of bone defects in animal models with positive outcomes. In this study, we explored a pre-manufactured hydrogel system containing the Li ion (Li-gel) in bone applications. Human MSCs cultured in this Li-gel exhibited enhanced osteogenic differentiation. Furthermore, this Li-gel was used to treat chick embryo chorioallantoic membrane (CAM) femur defects and enhanced the bone healing process.

The poor affinity of rhBMP-2 to the scaffolds leads to high dose administration requirement resulted in massive side effects has been the hurdle for successful clinic translation for treating delayed unions or remained non-union at bone defect. Optimizing the scaffolds with the purpose of obtaining optimal BMP2 dose and release have been addressed as critical for BMP-2 administration, however, the results are contradictory concerning whether bone formation is more beneficial from burst or controlled release of BMP2. While this might be due to these studies incorporated other bioactive molecules onto scaffolds to immobilize BMP-2. In this study, we report the affinities of rhBMP-2 to the scaffolds can be improved by only tuning the pH of hyaluronic acid (HA) hydrazone crosslinking hydrogel without addition of other molecules. Neo bone induced by BMP-2 showed significantly higher volume with more impact structure and vascularization in pH 4.5 HA hydrogel compared to that in pH7 HA hydrogel. The mechanisms were demonstrated by In vitro BMP-2 release followed by diffusion quantitative calculation and computational simulation methods. Initial burst release of BMP-2 from pH 7 HA hydrogels with the fitting of Fickian behavior while sustained release from pH 4.5 HA hydrogel was observed. Computational stimulation revealed this is due to the protonation state of BMP2 at pH 4.5 resulted in stronger electrostatic interaction with negatively charged groups along the backbone of hyaluronic acid molecules compared to at pH 7. This study gives new direction to scaffolds designing for basic bioactive protein applications in future.