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Poly(aspartic acid) (PASP) is an environmentally friendly biopolymer used as a fertilizer synergist and known to increase agricultural yields. The mechanism of PASP enhancement has, however, not been established, although the general hypothesis is that the polymer functions to hold nutrients closer to the root zone. The objective of this study was to determine the physiological and molecular changes that occur when plants are exposed to PASP, with future directions leading to a proposed mode of action. A whole genome transcriptome study was conducted. Arabidopsis thaliana seeds were germinated and grown in sterile plates treated with 250 ppm PASP under continuous light. Total RNA was extracted from whole seedlings and sequenced. The results revealed 462 differentially expressed genes (DEGs), 245 of which were upregulated and 217 downregulated. Gene Ontology, KEGG and MAPman analyses revealed DEGs involved in photosynthesis with 11 light harvesting complexes upregulated (e.g. LHCB1.1, LHCB2.2, LHCA1, LHCB4.2, LHCB2.1, LHCA4, LHCB1.1, LHCB3, LHCA3); the peroxisome pathway had 6 DEGs (CAT1, KAT1 and XDH2) upregulated (CSD1, CSD2 and FSD2) downregulated, the phenylpropanoid biosynthesis pathway had 7 DEGs upregulated. Other key DEGs were associated with the amino acid (e.g. ASN1) and nitrogen metabolism pathways. Physiology assessment results showed significant differences between control and treated plants with a 33 % increase in leaf area, 25 % increase chlorophyll content (p ≤ 0.05) and a 4-fold increase in photosynthetic rate (p ≤ 0.001). This information helps to increase our understanding of the key genes and metabolic pathways associated with plant response to PASP.

Poly(aspartic acid) (pAsp)-based fiber networks were developed via electrospinning and photo-crosslinking. Fiber networks hold the advantage that they exhibit a high surface-to-volume ratio, giving rise to a high water uptake and retention capacity, along with the ability to release moisture under desired circumstances (e.g. reduced relative humidity, mechanical pressure, etc.). Herein, polysuccinimide (PSI), the precursor of pAsp, was modified with 5-norbornene-2-methylamine to obtain crosslinkable norbornene-modified PSI (PSI-NB) with two different degrees of substitution, i.e. 19% and 46%. These derivatives were electrospun into thin uniform fibers after optimization of the processing parameters. The fiber sheets were crosslinked via a thiol-ene step-growth mechanism with three different thiol crosslinkers exploiting UV-A irradiation in the presence of TPO-L as photo-initiator. Using this strategy, fiber networks with diameters ranging between 1.27 ± 0.29 and 2.20 ± 1.05 µm were obtained, as visualized with scanning electron microscopy (SEM). Successful crosslinking was evidenced by a dissolution test in dimethylformamide and through X-ray photoelectron spectroscopy. Finally, the PSI-NB fiber networks were hydrolyzed to obtain pAsp-NB fiber networks by alkaline hydrolysis in a carbonate buffer solution, as confirmed by Fourier-transform infrared spectroscopy. The morphology of the fibers following hydrolysis was visualized by SEM and the average fiber diameters were calculated and compared to the diameters before hydrolysis, generally showing a diameter increase due to swelling of the fibers in aqueous solution. In conclusion, pAsp-based fiber networks were successfully developed and stabilized via photo-crosslinking.

The adsorption mechanism of different polymers containing ionic polyamino acids monomers in the chain structure at the solid–liquid interface was investigated. Initially, the influence of molecular weight and solution pH on simple polyamino acids (poly(L-aspartic acid) and poly(L-lysine) binding was determined. Considering the obtained dependencies, the polymer adsorption layer conformation was proposed in the systems containing block copolymers (both diblock and symmetrical triblock) consisting of polypeptide as well as poly(ethylene glycol) fragments. The presented studies focused on the application of two experimental methods. The polymer adsorption was carried out using the batch method and the adsorbate concentration was determined spectrophotometrically. Then, the turbidimetric measurements were taken. The analysis of the obtained results showed that the adsorption process of block copolymers depends on two factors. Firstly, the solution pH determines both the nature of the interactions of the copolymer structural units with the solid surface and the conformation of the polypeptide chains. The second parameter influencing the adsorption layer structure is the ratio of the lengths of both blocks. Introducing a short PEG fragment into the polymer main chain may improve the polymer adsorption properties by increasing the number of interactions with the adsorbent surface. [ABSTRACT FROM AUTHOR]

With biocompatibility and biodegradability, self-healing hydrogels prepared from biopolymers show great advantages in bioengineering and bioscience as drug delivery carrier. In this research, the biodegradable hydrogel was constructed based on poly(amino acid) of poly(aspartic acid) (PAsp) and pectin for in vivo antitumor applications as DOX release carrier. The PAsp bearing hydrazide groups and isopropyl groups (PAPH) was synthesized by ring opening of polysuccinimide (PSI) by isopropylamine and hydrazine, and used to fabricate fully biodegradable hydrogel with oxidized pectin (OPec) through dynamic acylhydrazone bond cross-linking. The regulatable mechanical strength of the hydrogel could adapt its bioapplication, and the excellent biocompatibility ensured biosafety in biomedical areas. Furthermore, the pectin backbone and the PAsp endowed the hydrogel with biodegradability both by enzyme and in vivo. The PAPH/Opec hydrogel as DOX carrier inhibited the tumor growth with the tumor weight 80% lower than the control group and reduced the in vivo toxicity of the DOX. As a result, this biodegradable PAPH/Opec hydrogel could find show great potential as sustained drug delivery vehicle in biomedical areas. [ABSTRACT FROM AUTHOR]

The onset of osteoporosis leads to a gradual decrease in bone density due to an imbalance between bone formation and resorption. To achieve optimal drug efficacy with minimal side effects, targeted drug delivery to the bone is necessary. Previous studies have utilized peptides that bind to hydroxyapatite, a mineral component of bone, for bone‐targeted drug delivery. In this study, a hydroxyapatite binding (HAB) tag is fused to 30Kc19α‐Runt‐related transcription factor 2 (RUNX2) for bone‐targeting. This recombinant protein can penetrate the nucleus of human mesenchymal stem cells (hMSCs) and act as a master transcription factor for osteogenesis. The HAB tag increases the binding affinity of 30Kc19α‐RUNX2 to mineral deposition in mature osteoblasts and bone tissue, without affecting its osteogenic induction capability. In the osteoporosis mouse model, intravenous injection of HAB‐30Kc19α‐RUNX2 results in preferential accumulation in the femur and promotes bone formation while reducing toxicity in the spleen. These findings suggest that HAB‐30Kc19α‐RUNX2 may be a promising candidate for bone‐targeted therapy in osteoporosis. [ABSTRACT FROM AUTHOR]

Concrete is currently the most used man-made construction material. Unfortunately it is prone to defects, such as cracks. Crack repair is possible by incorporation of superabsorbent polymers (SAPs) which can fill a crack by swelling and promote formation of healing products. However, SAPs are usually acrylate-based and not biodegradable. Present work focuses on development of SAPs based on poly(aspartic acid) (PASP), which is a biobased and biodegradable alternative of acrylate-based polymers. The developed SAP was incorporated in mortar and the effect on the mortar properties was studied. When adding 1 m% SAP, a decrease in strength was observed, similar to commercially available acrylate-based SAPs. The SAPs showed an efficient and immediate sealing effect in cracked mortar, reflected by a reduction in water permeability over 50%. Hence, the developed biobased SAP shows good sealing properties and could be used as a sustainable alternative for acrylic SAPs in concrete repair. [ABSTRACT FROM AUTHOR]

In this work, nanoparticles of the chitosan-poly((α,β)-DL-aspartic acid) polyelectrolyte complex (PEC) were synthesized. The purpose is to develop a biodegradable, biocompatible, and non-toxic polymeric platform as a vehicle for the encapsulation of hydrophilic drugs. The ionotropic gelation method, using solutions of chitosan and poly((α,β)-DL-aspartic acid sodium salt), allowed synthesizing particles with diameters of 142.1 ± 2.9 nm determined by DLS, while by FESEM particle diameters in the 60–200 nm range were observed. A preliminary trial showed that encapsulation of isoniazid, a hydrophilic drug to treat tuberculosis, is possible with encapsulation efficiency in the range of 5.3–5.8%. [ABSTRACT FROM AUTHOR]

Vanillin (VLN) is generally used in bakery food products as an aroma enhancer and flavoring agent. Hence it is important to develop a powerful and rapid tool to monitor the concentration of VLN levels concerning food safety. In this paper, a simple sensor was proposed by electropolymerized Aspartic acid (ASP) modified on Graphene and Graphite composite paste electrode (PASPMGN/CPE) for the detection of VLN by differential pulse voltammetry (DPV). PASPMGN/CPE ranked to have high electrocatalytic kinetics towards electro‐oxidation of VLN, in optimized conditions. The electrochemical process of VLN is portrayed to be irreversible and adsorption‐controlled kinetics by the cyclic voltammetry (CV) method. The surface features were studied using Field Emission Scanning Electron Microscopy (FE‐SEM), Energy Dispersive X‐ray Spectroscopy (EDX), Electrochemical Impedance Spectroscopy (EIS) and CV. From DPV results, the oxidative peak current showed linear growth toward the concentration of VLN ranging from 1.0 μM to 15.0 μM with a limit of detection and quantification of 4.85 μM and 16.2 μM. The modified sensor attained to be highly selective with common possible interferents. PASPMGN/CPE was efficient in detecting VLN in vanilla pods, essence and bakery product samples. [ABSTRACT FROM AUTHOR]

The innovation of N fertilizer and N management practices is essential to maximize crop yield with fewer N inputs. A long-term field fertilization experiment was established in 2015 on the North China Plain (NCP) to determine the effects of a control treatment (CN) and the eco-friendly material poly(aspartic acid)-coated urea (PN), applied as a one-time basal application method, on winter wheat yield and N use efficiency at four N application rates: 0 (N0), 63 (N63), 125 (N125), and 188 (N188) kg N ha1. The results indicated that compared to CN, PN resulted in a significant increase in wheat yield by 9.6% and 9.2% at N63 and N125, respectively, across the three experimental years, whereas no significant (p < 0.05) difference was detected at N188. Leaf area duration (LAD), crop growth rate (CGR), and dry matter accumulation (DMA) increased with increasing N rates, while PN significantly increased LAD and CGR by 5.1%-16.4% and 5.4%-64.3%, respectively, during the anthesis-ripening growth stage and DMA by 13.7% and 10.1% at N63 and N125, respectively, after the anthesis stage compared to CN. During the grain-filling stage, PN significantly increased the kernel maximum grain-filling rate (Gmax) by 21.7% and the kernel weight at the maximum grain-filling rate (Wmax) by 6.7% at N125 compared to CN. Additionally, compared to CN, PN significantly improved the stover and grain N content at harvest and increased NUT, NPFP, and NAE by 5.7%-40.1%, 2.5%-23.3%, and 3.9%-42.8%, respectively, at N63-N125. Therefore, PN applied using a single basal nitrogen fertilizer application method showed promising potential in maintaining a stable wheat yield and increasing N use efficiency with a 33% urea cut (approximately 63 kg N ha-1) compared to CN at the current wheat yield level on the NCP. [ABSTRACT FROM AUTHOR]

Stimuli-responsive hydrogels are attracting extensive attention in drug delivery system. Here, a novel pH, thermo and salt sensitivity of composite hydrogels was synthesized in situ from polysuccinimide modified by γ-aminopropyltriethoxysilane with mesoporous molecular sieves (MCM-41) as only crosslinking agent for controlled salicylic acid release. Morphologies and thermal behaviors of KPAsp/MCM-41 hydrogels were characterized by scanning electron microscopy and thermogravimetric analysis. Swelling dynamic behaviors, pH, thermo and salt sensitivities and drug releasing capacities of composite hydrogels were also systematically investigated. The obtained results show that multi-responsive hydrogels are very sensitive to environmental pH, external temperature and ionic valence, which indicated that the MCM-41 addition not only can ameliorate the network structure, but also can enhance the drug loading and releasing capacity. The controlled salicylic acid release rates of MCM-41/KPAsp hydrogels can reach to 33.6% and 61.2% in simulated gastric fluid (pH = 1.2) and in simulated intestinal fluid at (pH = 7.4) at 37 °C, respectively. The as-synthesized multi-responsive hydrogels reported here are promising candidates for application in targeted drug delivery system. [ABSTRACT FROM AUTHOR]

Hydrogels as wound dressing have attracted extensive attention in past decade because they can provide moist microenvironment to promote wound healing. Herein, this research designed a multifunctional hydrogel with antibacterial property and antioxidant activity fabricated from quaternary ammonium bearing light emitting quaternized TPE-P(DAA-co-DMAPMA) (QTPDD) and poly(aspartic hydrazide) (PAH). The protocatechuic aldehyde (PCA) grafted to the hydrogel through dynamic bond endowed the hydrogel with antioxidant activity and the tranexamic acid (TXA) was loaded to enhance the hemostatic performance. The hydrogel possesses preferable gelation time for injectable application, good antioxidant property and tissue adhesion, improved hemostatic performance fit for wound repairing. Furthermore, the hydrogel has excellent antimicrobial property to both E. coli and S. aureus based on quaternary ammonium structure. The hydrogel also showed good biocompatibility and the in vivo experiments proved this hydrogel can promote the wound repairing rate. This study suggests that TXA/hydrogel with quaternary ammonium structure and dynamic grafted PCA have great potential in wound healing applications. • Quaternary ammonium bearing copolymer QTPDD was synthesized through two step reaction. • The antibacterial hydrogel with biodegradability was prepared QTPDD and PAH. • Protocatechualdehyde with antioxidant activity was grafted onto the hydrogel by dynamic bond. • Tranexamic acid was loaded to the hydrogel to enhance the hemostatic performance of the hydrogel. • The multifunctional hydrogel showed good hemostatic property and enhance the wound healing. [ABSTRACT FROM AUTHOR]

Polymer hydrogels are ideal scaffolds for both tissue engineering and drug delivery. A great advantage of poly(amino acid)-based hydrogels is their high similarity to natural proteins. However, their expensive and complicated synthesis often limits their application. The use of poly(aspartic acid) (PASP) seems an appropriate solution for this problem due to the relatively cheap and simple synthesis of PASP. Using amino acids not only as building blocks in the polymer backbone but also as cross-linkers can improve the biocompatibility and the biodegradability of the hydrogel. In this paper, PASP cross-linked with cystamine (CYS) and lysine-methylester (LYS) was introduced as fully amino acid-based polymer hydrogel. Gels were synthesized employing six different ratios of CYS and LYS. The pH dependent swelling degree and the concentration of the elastically active chain were determined. After reduction of the disulfide bonds of CYS, the presence of thiol side groups was also detected. To determine the concentration of the reactive cross-linkers in the hydrogels, a new method based on the examination of the swelling behavior was established. Using metoprolol as a model drug, cell proliferation and drug release kinetics were studied at different LYS contents and in the presence of thiol groups. The optimal ratio of cross-linkers for the proliferation of periodontal ligament cells was found to be 60−80% LYS and 20−40% CYS. The reductive conditions resulted in an increased drug release due to the cleavage of disulfide bridges in the hydrogels. Consequently, these hydrogels provide new possibilities in the fields of both tissue engineering and controlled drug delivery.

In this communication, poly(aspartic acid) (pAsp), its fluorescently labeled conjugate with lucifer yellow ethylenediamine (pAsp–LY), and 2,2-dimethyl-1,3-propanediamine-derived cationic polyaspartamide (pDmpa) were synthesized by liquid-phase method. Octamer of L-aspartic acid (L-Asp8) was also obtained by solid-phase synthesis. pDmpa interacted with both pAsp and model plasmid DNA to form compact nanosized interpolymer complexes, which showed different colloidal properties. Effective cellular uptake of pAsp–LY by NIH 3T3 fibroblasts was detected by confocal microscopy. Pre-complexation of pAsp–LY with pDmpa did not noticeably increase intracellular accumulation of the conjugate. Both pAsp and L-Asp8 were found to increase viability of murine 3T3 cells and human skin fibroblasts at μg/mL concentrations according to the MTT assay (24 h). This effect was observed along with moderate prooxidant activity of the peptides in the cells according to the DCFDA fluorescence assay. The results suggest that aspartic acid-based peptides per se are capable of penetrating mammalian cells and affecting their metabolic activity. The peptides can be complexed with their cationic derivative, i.e., pDmpa polyaspartamide, to develop nanosized formulations of pAsp and its conjugates. [ABSTRACT FROM AUTHOR]

Poly(aspartic acid) (PASP) hydrogels have gained significant attention in recent years due to their excellent biocompatibility, biodegradability and tunable swelling behavior. This comprehensive review presents an overview of past and current research efforts focusing on PASP hydrogels, their functionalization strategies, processing methods and applications. The chemical functionalization of PASP is addressed, highlighting the ability to tailor the functionalities of PASP for customization. Precise control over functional groups for crosslinking enables the preparation of PASP hydrogels that can respond to environmental triggers, rendering them valuable for applications including, yet not limited to, controlled drug release, tissue engineering and self-healing concrete. Furthermore, the processing methods employed to produce PASP in different forms, such as films, nanoparticles and fibers are described. Finally, the applications of PASP hydrogels are overviewed, highlighting their potential to help improving human health and environmental sustainability by providing an alternative for fossil-based hydrogels. [Display omitted] [ABSTRACT FROM AUTHOR]

This review presents an overview on the recent progress in the synthesis, crosslinking, interpenetrating networks, and applications of poly(aspartic acid) (PASP)-based hydrogels. PASP is a synthetic acidic polypeptide that has drawn a great deal of attention in diverse applications due particularly to its biocompatibility and biodegradability. Facile modification of its precursor, poly(succinimide) (PSI), by primary amines has opened a wide window for the design of state-of-the-art hydrogels. Apart from pH-sensitivity, PASP hydrogels can be modified with suitable species in order to respond to the other desired stimuli such as temperature and reducing/oxidizing media as well. Strategies for fabrication of nanostructured PASP-based hydrogels in the form of particle and fiber are also discussed. Different cross-linking agents for PSI/PASP such as diamines, dopamine, cysteamine, and aminosilanes are also introduced. Finally, applications of PASP-based hydrogels in diverse areas particularly in biomedical are reviewed.

Highlights • An environmentally friendly MPASPs was put forward and synthesized. • PEM and SPA were introduced into PASP to improve the performance of superplasticizer. • The MPASPs could improve the fluidity of cement paste and the strength of cement mortar. • The MPASPs could inhibit early cement hydration while had little effect on later cement hydration. Abstract The environmentally friendly polycarboxylate superplasticizer based on modified poly(aspartic acid) (MPASPs) with varied grafting densities were prepared by partially ring-opening reaction of polysuccinimide (PSI) with polyetheramine M2005 (PEM) and sodium p-aminobenzenesulfonate (SPA) and subsequently hydrolyzing of the remaining imide ring under mildly alkaline conditions. FTIR was used to characterize the MPASPs. The properties of the MPASPs were evaluated by fluidity of cement paste, flexural strength of hardened cement mortar, adsorption amount on cement particle surface, zeta potential of cement paste, XRD and TG-DSC analysis. The results revealed that the MPASPs with proper incorporation of polyether side chains and benzene sulfonic acid groups could improve the fluidity of cement paste and the mechanical property of cement mortar. The fluidity of cement paste doped with MPASP-3 was 197% higher than that of PASP, and the cement mortar with MPASP-3 shown the highest flexural strength at both ages of 7 d and 28 d. The MPASPs could inhibit the early cement hydration while had little effect on later cement hydration. Based on the above results, the dispersion model of MPASPs in cement–water system was also discussed. This study offered a novel environmentally friendly superplasticizer based on a biodegradable green polymer and simple synthesis method. [ABSTRACT FROM AUTHOR]

Bone infection is a feared complication for patients with surgically fixed bone fractures and local antibiotic delivery is important in prophylaxis and treatment of these infections. Recent studies indicated that Staphylococcus aureus can penetrate bone tissue through micron-sized canaliculi and evade systemic and currently available local antibiotic treatments. Targeting bacteria within the bone requires highly efficient delivery of antimicrobials to the infected bone tissue. In this work, a biodegradable microsphere carrier loaded with antibiotics and with specific affinity to bone mineral was developed. Two widely used antibiotics, i.e., Gentamicin-dioctyl sulfosuccinate (GM-AOT) and Ciprofloxacin (CF) were embedded in poly(ϵ-caprolactone) (PCL) microspheres fabricated by oil-in-water emulsion techniques with carboxylated poly(vinyl alcohol) (cPVA) as surfactant. The carboxylic acid groups present at the Poly(ϵ-caprolactone)/cPVA (PCL-cPVA) microsphere surface were functionalized with aspartic acid oligomers (ASP) granting bone targeting properties. We report on cPVA synthesis, microsphere formulation, and antibiotic loading of PCL/cPVA-ASP microspheres. Antibiotic loaded PCL/cPVA-ASP microspheres show sustained release of its antibiotic load and can inhibit bacterial growth in vitro for up to 6 days. PCL/cPVA-ASP microspheres show enhanced affinity to mineralized substrates compared to non-functionalized PCL/cPVA microspheres. These findings support further development of these bone targeting antibiotic carriers for potential treatment of persistent bone infections.

A 2,4,6-trinitrobenzenesulphonic acid (TNBS)-based assay is developed to determine the degree of chemical cross-linking in aspartic acid-based polymer gels. The conventional colourimetric method for the quantitative determination of amine groups is difficult to use in polymer networks; thus, an improved method is developed to analyse polymer gels swollen in dimethyl sulfoxide (DMSO). Reaction products of the derivatizing reaction are examined by NMR. The chemical stability of the reagent is increased in DMSO, and the method shows satisfactory linearity and accuracy. The degree of chemical cross-linking in the investigated gels is close to its theoretical maximum, but the conversion of the pendant amine groups to cross-linking points is strongly dependent on the feed composition of the gels.

Abstract The synthesis of a chemically cross-linked polymer hydrogel consisting exclusively of amino acids is described in this paper. A natural amino acid, aspartic acid was polymerized to polysuccinimide which was cross-linked by a tetrapeptide sequence designed for proteolytic degradation, and then the corresponding poly(aspartic acid) hydrogel was obtained by alkaline hydrolysis. The hydrogel dissolved in the presence of trypsin. According to in vitro cellular assays, the degradation products of the hydrogel cross-linked with the peptide were non-cytotoxic and non-cytostatic. The sustained release of an encapsulated macromolecular model drug, FITC-dextran, was triggered by the degradation of the hydrogel induced by trypsin. These results suggest the potential application of the trypsin-responsive hydrogel for drug delivery in the small intestine. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

While curcumin has a broad range of beneficial properties such as anticancer, antioxidant and antibacterial activities, its poor solubility, low stability and non-selectivity toward tumor cells often limit its applications. Herein, we described the preparation and characterization of a new fully biocompatible graft copolymer from folic acid/amylose-functionalized poly(aspartic acid) (FA-PAsp-Am) as an effective nanocarrier using a simple aminolysis method. The inclusion complex formation ability of amylose (Am) with curcumin (Cur) as well as its glycotargeting ability when it grafted to the polyaspartic acid (PAsp) backbone as a side chain, could impart more selectivity to tumor cells, promote the solubility of curcumin and improve its stability against UV–Visible irradiation, as demonstrated by UV–Visible exposure test results. The obtained data from FT-IR, H-NMR, Fluorescence, SEM, DLS and UV–Visible techniques confirmed the successful synthesis of the polymer nanocarrier. The observed nanofiber like morphology (20 nm width by SEM) of the nanocarrier and the host-guest interaction of curcumin with the amylose helices facilitate the high efficiency of the drug loading. The influence of pH, on the curcumin release behavior also was assessed. Furthermore, the antioxidant ability of curcumin was largely maintained after the loading in the FA-PAsp-Am system. These properties collectively make the folic acid (FA) functionalized poly(aspartic acid)-graft-amylose@curcumin of potential interest for various biomedical applications such as targeted drug delivery systems. [ABSTRACT FROM AUTHOR]

In this work, modified attapulgite/poly(aspartic acid) (MATP/PAsp) composite superabsorbent resin with 3-D network structure was prepared by the method of solution polymerization, wherein we used polysuccinimide(PSI) as interdiemate, attapulgite (ATP) as the filling material, γ-aminopropyl triethoxysilane (KH-550) as the modifier, and 1,6-hexamethylenediamine as the crosslinking agent. For further identification of microstructures of this resin, transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were adopted. Influences of the particle size, addition, and modification time on the absorbency performances of resin were investigated respectively. It was found that there is a significant improvement in micro structure with the introduction of MATP, and the water absorbency and retention performance were also increased. The optimum MATP/PAsp composite resin was obtained under condition of particle size range of 45 µm-54 µm, addition dopant of 2wt%, modification time of 6.5 h. The swelling ratio of composite resin in distilled water and normal saline were 892 g g−1 and 95 g g−1, respectively, which had 23% and 30% increase compared the case of none-composite resin samples. The water-retention rate for composite resin was measured to be 66.12% after 6 h's constant temperature drying at 50℃, which is higher by 7.72% than none-composite resin. [ABSTRACT FROM AUTHOR]

Poly(amino acid) based self-healing hydrogels have important application in biomedications. In this research, the catechol pendant groups were imported to poly(aspartic acid) based self-healing hydrogel to improved skin adhesion and ROS scavenging performance. The poly(succinimide) (PSI) was reacted with 3,4-dihydroxyphenylalanine (DA) and then hydraziolyzed to import catechol group and hydrazide group respectively, which are responsible for mussel inspired tissue adhesion and dynamic coupling reactivity. The dopamine modified poly(aspartic hydrazide) (PDAH) was reacted with PEO 90 dialdehyde (PEO 90 DA) to prepare hydrogels, and the resultant hydrogel showed good biocompatibility both in vitro and in vivo. The skin adhesion strength of the mussel inspired hydrogel increased notably with enhanced radical scavenging efficiency fit for in vivo wound repairing applications. The PDAH/PEO 90 DA hydrogel also showed sustained albumin release profile and the in vivo wound repairing experiment proved the mouse Epidermal Growth Factor (mEGF) loaded hydrogel as wound dressing material accelerated the wound repairing rate. [Display omitted] • The PSI was reacted with dopamine and hydrazine to synthesis catechol bearing poly(aspartic hydrazide) PDAH. • The PDAH was reacted with PEO 90 DA to fabricate hydrogels through dynamic hydrazone bonds. • The catechol bearing self-healing hydrogel showed enhanced ROS scavenging performance and tissue adhesion. • The hydrogel with mEGF loading accelerated the wound repairing rate in mice model. [ABSTRACT FROM AUTHOR]

New amphiphilic PEGylated poly(aspartic acid) graft copolymer (PASP-PEG-Ph) was synthesized as a nanocarrier for intravaginal drug delivery of poorly water-soluble drugs. PASP-PEG-Ph self-assembled into negatively charged spherically shaped nanoparticles in the presence of pH 4.5 and pH 7.0 vaginal fluid simulants with a diameter of approximately 200 nm as evidenced by Zeta-potentiometer, scanning electron microscope (SEM), dynamic light scattering (DLS) analysis. A significant number of stable NPs could be maintained at pH 4.5, 37 °C for 13 days. The PASP-PEG-Ph NP showed no significant cytotoxicity toward the T-cell line SupT1 and human vaginal epithelial cell line Vk2/E6E7 up to 1 mg/mL. The highest encapsulation efficiency of the model drug coumarin 6 (C6) by PASP-PEG-Ph was 92.0 ± 5.7%. The sustained release profile of the encapsulated C6 was demonstrated by anin vitrorelease study. Anin vitrocellular uptake study revealed strong cellular uptake of the C6 loaded NP by SupT1 cells within 2 h. [ABSTRACT FROM PUBLISHER]

A novel multifunctional nanosystem formed by magnetite nanoparticles coated with pH-responsive poly(aspartic acid) hydrogel was developed. Magnetite nanoparticles (Fe 3 O 4 ) have been intensively investigated for biomedical applications due to their magnetic properties and dimensions similar to the biostructures. Poly(aspartic acid) is a water-soluble, biodegradable and biocompatible polymer, which features makes it a potential candidate for biomedical applications. The nanoparticles surface modification was carried out by crosslinking polysuccinimide on the magnetite nanoparticles surface and hydrolyzing the succinimide units in mild alkaline medium to obtain the magnetic poly(aspartic acid) hydrogel. The surface modification in each step was confirmed by DRIFTS, TEM and zeta potential measurements. The hydrodynamic diameter of the nanosystems decreases as the pH value decreases. The nanosystems showed high colloidal stability in water and no cytotoxicity was detected, which make these nanosystems suitable for biomedical applications. [ABSTRACT FROM AUTHOR]

Macromolecular co-assemblies built up in aqueous solutions, by using a linear polypeptide, poly(aspartic acid) (PAS), and a globular protein, bovine serum albumin (BSA), have been studied. The main interest was to identify the optimum conditions for an interpenetrated complex formation in order to design materials suitable for biomedical applications, such as drug delivery systems. BSA surface possesses several amino- and carboxylic groups available for covalent modification, and/or bioactive substances attachment. In the present study, mixtures between PAS and BSA were investigated at 37 °C in dilute aqueous solution by viscometry, dynamic light scattering and zeta potential determination, as well as in solid state by AFM microscopy and dielectric spectroscopy. The experimental data have shown that the interpolymer complex formation occurs for a PAS/BSA molar ratio around 0.541. [ABSTRACT FROM AUTHOR]

Poly(aspartic acid) (PASP) derivatives with adjustable pH-dependent solubility were synthesized and characterized to establish the relationship between their structure and solubility in order to predict their applicability as a basic material for enteric coatings. Polysuccinimide, the precursor of PASP, was modified with short chain alkylamines, and the residual succinimide rings were subsequently opened to prepare the corresponding PASP derivatives. Study of the effect of the type and concentration of the side groups on the pH-dependent solubility of PASP showed that solubility can be adjusted by proper selection of the chemical structure. The Henderson–Hasselbalch (HH) and the extended HH equations were used to describe the pH-dependent solubility of the polymers quantitatively. The estimate provided by the HH equation is poor, but an accurate description of the pH-dependent solubility can be found with the extended HH equation. The dissolution rate of a polymer film prepared from a selected PASP derivative was determined by fluorescence marking. The film dissolved rapidly when the pH was increased above its pK a . Cellular viability tests show that PASP derivatives are non-toxic to a human cell line. These polymers are thus of great interest as starting materials for enteric coatings. Statement of Significance Poly(amino acid) type biocompatible polymers were synthesized for future use as pharmaceutical film coatings. To this end, we tailored the pH-dependent solubility of poly(aspartic acid) (PASP). It was found that both the solubility and the pK a values of the modified PASP depended strongly on composition. Fluorescent marking was used to characterize the dissolution of a chosen PASP derivative. In acidic media only a negligible amount of the polymer dissolved, but dissolution was very fast and complete at the pH values that prevail in the small intestine. As a consequence, enteric coatings based on such PASP derivatives may be used for drug delivery in the gastrointestinal tract. [ABSTRACT FROM AUTHOR]

A novel biodegradable sodium poly(aspartic acid) (PASP) hydrogel with microporous structure was manufactured using electrospun polysuccinimide (PSI) nanofibers. PSI is the intermediate of sodium PASP and could be electospun into nanofibers easily. Firstly, PSI nanofibers were prepared from PSI/N, N-dimethylformamide solution. Then the PSI nanofibrous mats were crosslinked and hydrolyzed to obtain biodegradable microporous sodium PASP nanofibrous hydrogels. The chemical structures, morphologies and pore sizes of PSI nanofibrous mats and microporous sodium PASP nanofibrous hydrogels were investigated. Moreover, the properties of PSI electrospinning solutions, and the swelling ratio and biodegradability of sodium PASP hydrogels were also examined. The results showed that the swelling ratio of microporous sodium PASP nanofibrous hydrogels achieved to 21.0-24.3 g/g and were obviously higher than that of the sodium PASP casting film, reporting a swelling ratio of only 4.6 g/g. When the microporous sodium PASP nanofibrous hydrogel was immersed in water, it exhibited quick absorption and morphological robustness. The microporous sodium PASP nanofibrous hydrogel showed 83 wt% weight loss after 7 days of trypsin catalyzed biodegradation, and the SEM analysis demonstrated the significant morphology change of the microporous sodium PASP nanofibrous hydrogel during the biodegradation. [ABSTRACT FROM AUTHOR]

A series of 14 cationic derivatives of poly(aspartic acid) i.e. cationic polyaspartamides with different (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups was synthesized by nucleophilic addition on polysuccinimide. The resulting polyaspartamides have moderate amphiphilic properties. Relationships between the structure and ratio of side groups and in vitro properties of polyaspartamides, including their cytotoxic and membrane-damaging activity towards human cell lines, primary skin fibroblasts and erythrocytes, were established and discussed. Cationic polyaspartamides vary in their DNA-binding, condensing and nuclease-protecting characteristics depending on the concentration ratio of (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups. Effective cell transfection was achieved upon polyaspartamide-mediated plasmid DNA delivery in serum-free medium in the presence of chloroquine. Effect of serum proteins adsorption onto polyaspartamide based polyplexes, and the role of concentration of polyplexes in culture medium in their colloidal stability and transfection process were demonstrated. Synthesized polyaspartamides are biocompatible and long-acting gene carriers, which are applied to cells after dilution and without washing, thus providing transfection level comparable to that of commercial transfection reagent. [ABSTRACT FROM AUTHOR]

Poly(aspartic acid) (PASP) hydrogels were prepared by crosslinking polysuccinimide (PSI) with diaminobutane followed by the mild hydrolysis of the resultant PSI gels to PASP hydrogels. The composition dependence of the gelation time and the stiffness of bulk PASP hydrogels were determined by rheometry and compression tests, respectively. The composition of the prepared PASP nanogels was chosen based on the results on bulk PASP hydrogels. Prior to nanogel preparation stability of DMSO-in-oil (inverse) emulsions was tested as a function of the chemical quality of apolar phase, the concentration of the precursor polymer and the concentration of the surfactant. PASP nanogels in the size of a few hundred nanometers were prepared by the hydrolysis of PSI nanogels synthesized in inverse emulsion. PASP nanogels showed pH-dependent swelling and strongly negative surface charge at physiological pH values, thus they can be further developed to meet the specific criteria of different bio-related applications. [ABSTRACT FROM AUTHOR]

Effect of poly(succinimide) (PSI) and poly(aspartic acid) (PASP) on free radical reactions and cell viability was assessed. Molecular weight (MW) of PASPs was determined by static light scattering technique and found as 3.9 and 8.3 kDa. Among PSIs and PASPs, only poly(aspartic acid) with higher MW was found to inhibit formation of hydroxyl-radical in Fenton's reaction, although each polymers studied were not able to eliminate diphenylpicrylhydrazyl radical. PASPs were almost non-toxic for 3 T3 fibroblasts and PC-3 cells (IC ≫ 3 mg/mL), whereas PSIs diminished cell viability with different IC values depending on cell type and polymer MW. Our preliminary data indicate the MW dependence of bioactivity of l-aspartic acid-derived polymers designed as drug carriers and biocompatible materials. [ABSTRACT FROM AUTHOR]

Protein–polyelectrolyte complexes (PPC) are playing an important role in a variety of chemical and biological processes, such as protein separation, enzyme stabilization, and polymer drug delivery. The present investigation is focused on evaluation of the PPC formation between a synthetic polypeptide (poly(aspartic acid) – PAS) and a natural protein (bovine serum albumin – BSA). The PPC obtained from PAS and BSA in different ratio was investigated by corroboration of various techniques of characterization as: spectroscopy, microscopy, thermogravimetric analysis, dynamic light scattering (DLS), and zeta potential determination, measurements which were performed in static and/or dynamic conditions. The static contact angle of the sample films was also determined in order to evaluate the changes brought upon surface free energy of the prepared PPCs in interdependence with the complexes composition. The critical conditions for complex formation in BSA–polyelectrolyte systems were underlined. The phenomenon was better evidenced in case of a ratio of 1/1 wt between the two polymers, both in static and/or dynamic conditions. [ABSTRACT FROM AUTHOR]

The polymer structure impact on the adsorption layer conformation formed on the chromium (III) oxide surface was investigated. As adsorbates, three macromolecular compounds were tested: poly( l-aspartic acid) homopolymer and two block copolymers containing the poly(amino acid) segments as well as the poly(ethylene glycol) ones in the chain structure. Due to the ionic nature of the poly(amino acid), all measurements were carried out as a function of solution pH value. The most probable polymer chain binding mechanism was determined on the basis of the values obtained from the adsorption, potentiometric titration, turbidimetry and thermogravimetry experiments. The acquired results indicate that the solution pH has a great influence on the adsorbed macromolecule conformation. Additionally, in the case of the block copolymers, the individual structural unit affinity for the solid particles can be modified by the pH changes. Therefore, a significant difference in the mass decrement measured for the systems at pH 3 and 10 can be explained by the contribution of electrostatic forces and hydrogen bond formation to the polymer adsorption mechanism. Structure of the adsorbed polymer layer determines also the suspension stability. The solid surface charge neutralization by the macromolecules bound to the CrO surface at pH 3 impairs the sample stability, whereas the presence of the extended polymer chains in the basic solution leads to the durability improvement. [ABSTRACT FROM AUTHOR]

Nanogels loaded with fluorescent dextran as a model drug are synthesized by the oxidation induced cross-linking of water soluble redox responsive thiolated poly(amino acid) in miniemulsion without the introduction of any cross-linker molecule. Two types of high energy methods, namely, ultrasonication and high pressure homogenization (HPH), are compared. Dynamic light scattering and transmission electron microscopy measurements confirm that spherical nanogels in 100-150 nm diameter range are prepared successfully by HPH method. Size and surface charge of the nanogels can easily be controlled by environmental pH. The release of encapsulated drug is triggered by the degradation of nanogels in reducing environment due to the cleavage of disulphide bonds. [ABSTRACT FROM AUTHOR]

Thermally synthesized poly(aspartic acid) (tPAA) is a bio-based, biocompatible, biodegradable, and water-soluble polymer that has a high proportion of β-Asp units and equivalent moles of D- and L-Asp units. Poly(aspartic acid) (PAA) hydrolase-1 and hydrolase-2 are tPAA biodegradation enzymes purified from Gram-negative bacteria. PAA hydrolase-1 selectively cleaves amide bonds between β-Asp units via an endo-type process, whereas PAA hydrolase-2 catalyzes the exo-type hydrolysis of the products of tPAA hydrolysis by PAA hydrolase-1. The novel reactivity of PAA hydrolase-1 makes it a good candidate for a biocatalyst in β-peptide synthesis. This mini-review gives an overview of PAA hydrolases with emphasis on their biochemical and functional properties, in particular, PAA hydrolase-1. Functionally related enzymes, such as poly( R-3-hydroxybutyrate) depolymerases and β-aminopeptidases, are compared to PAA hydrolases. This mini-review also provides findings that offer an insight into the catalytic mechanisms of PAA hydrolase-1 from Pedobacter sp. KP-2. [ABSTRACT FROM AUTHOR]

Poly(aspartic acid) (PASP) hydrogel is a type of biodegradable and biocompatible polymer with high water absorbing ability. Traditionally, the production of PASP hydrogel is expensive, complex, environmentally unfriendly, and consumes a large amount of organic solvents, e.g. dimethylformamide or dimethylsulfoxide. This study introduces a one-step synthesis of PASP resin, in which the organic phase was replaced by distilled water and γ-aminopropyltriethoxysilane was used as the cross-linker. Absorbent ability and characteristics were determined by swelling ratio, FTIR,13C SSNMR, and SEM. In vitro cytotoxicity evaluation and animal skin irritation tests showed the hydrogel has body-friendly properties. Preparing PASP hydrogel in aqueous solution is promising and finds its use in many applications. [ABSTRACT FROM AUTHOR]

The development of wound dressings with antibacterial activities and simultaneous pro-healing functions are always urgent in treating bacterial wound infection. Herein, a novel multifunctional self-healing hydrogel was designed and prepared by crosslinking quaternary ammonium/boronic acid modified poly(aspartic acid) and poly (vinyl alcohol) polymers with targeted peptide MP196- conjugated polydopamine. The formation of this hydrogel not only improves the biocompatibility of quaternary poly(aspartic acid), but also enhances antibacterial efficacy by pH-triggering dissociation under the low pH bacterial microenvironment. Moreover, precise photothermal treatment can be achieved. In vitro study suggested high synergistic antibacterial efficiency(∼100 %) under near-infrared light, significantly higher than a single antibacterial strategy (66.0–82.6 %). In vivo study suggested infected wounds treated with the hydrogel showed an optimal healing rate(92.0 %) after 7 days. The survival rate of the bacteria in the epidermal tissues was reduced to 2.3 %. Besides, the suitable self-healing property of this hydrogel facilitated its application in the diversity of wound shapes. Thus, the novel poly(aspartic acid) hydrogel might be a promising candidate for precise therapy of bacteria-infected wounds. [Display omitted] • Precise antibacterial therapy was introduced into a poly(aspartic acid) hydrogel. • The MP196 short peptide endowed PDA with targeted photothermal ability. • The hydrogel possessed both intrinsic and photothermal bactericidal effects. • The synergistic antibacterial effect promoted wound healing within 7 days. [ABSTRACT FROM AUTHOR]

The present investigation is focused on evaluation of self-assembling ability in aqueous solutions of two water soluble polymers: poly(aspartic acid) (PAS) and Pluronic F127 (PL). The intermolecular complexes, realized between polyacid and neutral copolymer surfactant in different ratios, have been studied by combining various characterization techniques as rheology, DLS, spectroscopy, microscopy, chemical imaging, and zeta potential determination, measurements performed in static and/or dynamic conditions. In static conditions, when the equilibrium state between PAS/PL polymeric pair was reached, and depending on the polymers mixture composition, and of experimental rheological conditions, positive or negative deviations from the additive rule are registered. Conformational changes of the macromolecular chains and correspondingly physical interactions are generated between PL and PAS for self-assembly and the formation of interpolymer complex as suprastructure with micellar configuration. The phenomenon was better evidenced in case of 1/1 wt ratio between the two polymers. In dynamic conditions of determination, during “in situ” evaluation of the hydrodynamic diameter, zeta potential and conductivity, when the equilibrium state is not reached and as result either the intermolecular bonds are not achieved, the self-assembling process is not so obvious evidenced. [ABSTRACT FROM AUTHOR]

Poly(aspartic acid) (PASP) hydrogel is a biodegradable and biocompatible polymer with high water absorbing ability. Traditionally, the production of PASP hydrogel consumes large amounts of organic solvents, i.e., dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). This traditional approach is now considered costly, complex and environmentally unfriendly due to required used solvent disposal. The present research explores two novel methods in preparing PASP hydrogel without organic solvent, by using hydrazine hydrate and ethylene glycol diglycidyl ether (EGDGE) or poly(ethylene glycol) diglycidyl ether (PEGDGE) as the cross-linkers. Absorbent ability and other characteristics are determined. Preparing PASP hydrogel in aqueous solution is promising and finds its use in many applications. [ABSTRACT FROM AUTHOR]

Chemically cross-linked poly(aspartic acid) (PASP) gels were prepared by a solid–liquid phase separation technique, cryogelation, to achieve a supermacroporous interconnected pore structure. The precursor polymer of PASP, polysuccinimide (PSI) was cross-linked below the freezing point of the solvent and the forming crystals acted as templates for the pores. Dimethyl sulfoxide was chosen as solvent instead of the more commonly used water. Thus larger temperatures could be utilized for the preparation and the drawback of increase in specific volume of water upon freezing could be eliminated. The morphology of the hydrogels was characterized by scanning electron microscopy and interconnectivity of the pores was proven by the small flow resistance of the gels. Compression tests also confirmed the interconnected porous structure and the complete re-swelling and shape recovery of the supermacroporous PASP hydrogels. The prepared hydrogels are of interest for several biomedical applications as scaffolding materials because of their cytocompatibility, controllable morphology and pH-responsive character. [ABSTRACT FROM AUTHOR]

Poly(aspartic acid) (PASP) hydrogel is a biodegradable and biocompatible polymer with high water absorbing ability. Traditionally, the production of PASP hydrogel consumes large amounts of organic solvents, i.e., dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). This traditional approach is now considered costly, complex and environmentally unfriendly due to required used solvent disposal. The present research explores two novel methods in preparing PASP hydrogel without organic solvent, by using hydrazine hydrate and ethylene glycol diglycidyl ether (EGDGE) or poly(ethylene glycol) diglycidyl ether (PEGDGE) as the cross-linkers. Absorbent ability and other characteristics are determined. Preparing PASP hydrogel in aqueous solution is promising and finds its use in many applications. [ABSTRACT FROM AUTHOR]