Biocompatible Crosslinker Research Articles

Gelatin-based hydrogels combined with electrical stimulation to modulate neonatal rat cardiomyocyte beating and promote maturation

Cardiovascular diseases are the leading cause of morbidity and mortality throughout the world underlining the importance of efficient treatments including disease modeling and drug discovery by cardiac tissue engineering. However, the predictive power of these applications is currently limited by the immature state of the cardiomyocytes. Here, we developed gelatin hydrogels chemically crosslinked by genipin, a biocompatible crosslinker, as cell culture scaffolds. Neonatal rat cardiomyocytes appear synchronous beating within 2 days after seeding on hydrogels. Furthermore, we applied the electrical stimulation as a conditioning treatment to promote the maturation of cardiomyocytes cultured on the hydrogels. Our results show that electrical stimulation improves the organization of sarcomeres, establishment of gap junctions, calcium-handling capacity and propagation of pacing signals, thereby, increase the beating velocity of cardiomyocytes and responsiveness to external pacing. The above system can be applied in promoting physiological function maturation of engineered cardiac tissues, exhibiting promising applications in cardiac tissue engineering and drug screening.

Human-scale tissues with patterned vascular networks by additive manufacturing of sacrificial sugar-protein composites

Combating necrosis, by supplying nutrients and removing waste, presents the major challenge for engineering large three-dimensional (3D) tissues. Previous elegant work used 3D printing with carbohydrate glass as a cytocompatible sacrificial template to create complex engineered tissues with vascular networks (Miller et al. 2012, Nature Materials). The fragile nature of this material compounded with the technical complexity needed to create high-resolution structures led us to create a flexible sugar-protein composite, termed Gelatin-sucrose matrix (GSM), to achieve a more robust and applicable material. Here we developed a low-range (25–37˚C) temperature sensitive formulation that can be moulded with micron-resolution features or cast during 3D printing to produce complex flexible filament networks forming sacrificial vessels. Using the temperature-sensitivity, we could control filament degeneration meaning GSM can be used with a variety of matrices and crosslinking strategies. Furthermore by incorporation of biocompatible crosslinkers into GSM directly, we could create thin endothelialized vessel walls and generate patterned tissues containing multiple matrices and cell-types. We also demonstrated that perfused vascular channels sustain metabolic function of a variety of cell-types including primary human cells. Importantly, we were able to construct vascularized human noses which otherwise would have been necrotic. Our material can now be exploited to create human-scale tissues for regenerative medicine applications. Statement of SignificanceAuthentic and engineered tissues have demands for mass transport, exchanging nutrients and oxygen, and therefore require vascularization to retain viability and inhibit necrosis. Basic vascular networks must be included within engineered tissues intrinsically. Yet, this has been unachievable in physiologically-sized constructs with tissue-like cell densities until recently. Sacrificial moulding is an alternative in which networks of rigid lattices of filaments are created to prevent subsequent matrix ingress. Our study describes a biocompatible sacrificial sugar-protein formulation; GSM, made from mixtures of inexpensive and readily available bio-grade materials. GSM can be cast/moulded or bioprinted as sacrificial filaments that can rapidly dissolve in an aqueous environment temperature-sensitively. GSM material can be used to engineer viable and vascularized human-scale tissues for regenerative medicine applications.

Development, characterization and evaluation of the biocompatibility of catechol crosslinked horsegram protein films

Proteins in the common legume Macrotyloma uniflorum have inherent antimicrobial properties and can be converted into films for food, medical and other applications. Crude proteins were extracted from horsegram seeds and were converted into thin films by casting approach. Amino acid analysis of the extracted protein confirmed the presence of both essential and non- essential amino acids required for food applications. However, the protein films have relatively weak mechanical properties and poor aqueous stability which can be substantially improved by crosslinking with a biocompatible crosslinker, catechol. Crosslinked films had strength of 7.32 MPa and were stable in water and cell culture media for upto 4 days suggesting their suitability for tissue engineering and other medical applications. The swelling % of the films was directly proportional to the amount of catechol used. The 20% catechol crosslinked films displayed significant antibacterial activity against Bacillus cereus and E. coli in comparison to the uncrosslinked films. In addition to demonstrating good antifungal activity against Aspergillus niger, the films were conducive to the growth of L929 mouse fibroblast cells, better than Zn @20 ppm. Overall, large availability, presence of essential amino acids, ability to develop films and other biomaterials with desired properties and cytocompatibility make horsegram proteins desirable for food, medical and other applications.

100th Anniversary of Macromolecular Science Viewpoint: Synthetic Protein Hydrogels.

Our bodies are composed of soft tissues made of various proteins. In contrast, most hydrogels designed for biological applications are made of synthetic polymers. Recently, it is increasingly recognized that genetically synthesized proteins can be tailored as building blocks of hydrogels with biological, chemical, and mechanical properties similar to native soft tissues. In this Viewpoint, we summarize recent progress in synthetic protein hydrogels. We compare the structural and mechanical properties of different protein building blocks. We discuss various biocompatible cross-linking strategies based on covalent chemical reactions and noncovalent physical interactions. We introduce how stimulus-responsive conformational changes or intermolecular interactions at the molecular level can be used to engineer responsive hydrogels. We highlight that hydrogel network structures are as important as the protein sequences for the properties and functions of protein hydrogels and should be carefully designed. Despite great progress and potentials of synthetic protein hydrogels, there are still quite a few unsettled challenges and unexploited opportunities, providing abundant room for future investigation and development, particularly as this field is quickly expanding beyond its initial stage. We discuss a number of possible directions, including optimizing protein production and reducing cost, engineering anisotropic hydrogels to better mimic native tissues, rationally designing hydrogel mechanical properties, investigating interplays of hydrogels and residing cells for 3D cell culture and organoid construction, and evaluating long-term cytotoxicity and immune response.

Are aqueous solutions of choline-based ionic liquid biocompatible cross-linkers for collagen?

Identification of biocompatible cross-linkers is extremely important in the field of biomaterials, as it aids in improving stability to protein but also elicits less immune response. Towards this, aqueous solution of choline-based ILs (CILs) has been keyed out as biocompatible cross-linkers with an aim to understand their impact and effect on stabilization of collagen. The changes in the hydration dynamics of collagen treated with aqueous solution of CILs has been probed using transverse NMR relaxation and impedance measurements. Upon treatment of aqueous solution of CILs with collagen, there is a reorientation in the surrounding water milieu suggesting compactness in the structure of collagen, which is indicative of crosslinking. Further, the conformational and thermal stability of collagen have been substantiated. It is ascertained that the helicity of collagen remains intact as witnessed from the Rpn values measured through circular dichroic measurements and shifts in frequencies of amide bands as measured through FT-IR measurements. A significant increase in the melting and denaturation temperature suggesting stability of collagen has been observed through DSC measurements. Aqueous solution of CILs treated collagen scaffolds have been further appraised for crosslinking efficiency, enzymatic stability, hemolytic and platelet attachment assays. The efficacy of aqueous solution of CILs treated scaffolds has been evaluated for biocompatibility with NIH-3T3 fibroblasts cells and further confirmed by the phase-contrast microscopic images of these cells. Interaction between the collagen and aqueous solution of choline-based ILs is typically anchored by non-covalent interactions like electrostatic, hydrogen, and van der Waals interactions. Therefore, the current study implies that the aqueous solution of CILs can be explored as biocompatible cross-linkers for collagen and thus can be employed for biomedical applications.

Proanthocyanidin-crosslinked collagen/konjac glucomannan hydrogel with improved mechanical properties and MRI trackable biodegradation for potential tissue engineering scaffolds.

Collagen (Col) has been intensively exploited as a biomaterial for its excellent biocompatibility, biodegradation and bioactivity. However, the poor mechanical properties and rapid biodegradation of reconstituted collagen hydrogels have always been the bottlenecks for their further development especially for vascular tissue engineering. Herein, based on the self-assembly characteristics of collagen, a ternary hydrogel scaffold, comprising rigid collagen molecules, flexible konjac glucomannan (KGM) chains and biocompatible crosslinkers of proanthocyanidin (PA), has been designed to achieve a synergistic interaction for essentially optimizing the mechanical properties of the so-obtained Col/KGM/PA hydrogel, which possesses not only substantially improved strength but also good elasticity. PA endows these scaffolds with controllable biodegradation and anti-calcification and antioxidant activities. TEM discovered the co-existence of two types of fibrils with distinctly different arrangement patterns, explaining the contribution of KGM macromolecules to elasticity generation. The in vivo variations of Col/KGM/PA implants are visualized in real-time by magnetic resonance imaging (MRI). Moreover, a quantitative technique of MRI T2-mapping combined with histology is designed to visualize the in vivo biodegradation mechanism of layer-by-layer erosion for these hydrogels. Simultaneously, three different relationships between the respective processes of in vivo degradation and in vivo dehydration of these controlled hydrogel implants were clearly revealed by this technique. Such a designed Col/KGM/PA composite hydrogel realizes the essential integration of good biocompatibility, controllable biodegradation and improved mechanical properties for developing a desired scaffold material for tissue engineering applications.

EAK Hydrogels Cross-Linked by Disulfide Bonds: Cys Number and Position Are Matched to Performances.

Hydrogels produced by self-assembling peptides are intrinsically biocompatible and thus appropriate for many biomedical purposes. Their application field may be even made wider by reducing the softness and improving the hydrogel mechanical properties through cross-linking treatments. To this aim, modifications of EAK16-II sequence by including Cys residues in its sequence were here investigated in order to obtain hydrogels cross-linkable through a disulfide bridge. Two sequences, namely, C-EAK and C-EAK-C, that contain Cys residues at the N-terminus or at both ends were characterized. Fiber-forming abilities and biological and dynamic mechanical properties were explored before and after the oxidative treatment. In particular, the oxidized version of C-EAK presents a good cell viability and sustains osteoblast proliferation. Furthermore, molecular dynamics (MD) simulations on monomeric and assembled forms of the peptides were performed. MD simulations explained how a specific Cys functionalization was better than the other one. In particular, the results suggested that EAK16-II functionalization with a single Cys residue, instead of two, together with biocompatible cross-linking may be considered an intriguing strategy to obtain a support with better dynamic mechanical properties and biological performances.

Force spectroscopy-based simultaneous topographical and mechanical characterization to study polymer-to-polymer interactions in coated alginate microspheres

Cell-laden hydrogel microspheres have shown encouraging outcomes in the fields of drug delivery, tissue engineering or regenerative medicine. Beyond the classical single coating with polycations, many other different coating designs have been reported with the aim of improving mechanical properties and in vivo performance of the microspheres. Among the most common strategies are the inclusion of additional polycation coatings and the covalent bonding of the semi-permeable membranes with biocompatible crosslinkers such as genipin. However, it remains challenging to characterize the effects of the interactions between the polycations and the hydrogel microspheres over time in vitro. Here we use a force spectroscopy-based simultaneous topographical and mechanical characterization to study polymer-to-polymer interactions in alginate microspheres with different coating designs, maintaining the hydrogels in liquid. In addition to classical topography parameters, we explored, for the first time, the evolution of peak/valley features along the z axis via thresholding analysis and the cross-correlation between topography and stiffness profiles with resolution down to tens of nanometers. Thus, we demonstrated the importance of genipin crosslinking to avoid membrane detachment in alginate microspheres with double polycation coatings. Overall, this methodology could improve hydrogel design rationale and expedite in vitro characterization, therefore facilitating clinical translation of hydrogel-based technologies.

Easy Applied Gelatin-Based Hydrogel System for Long-Term Functional Cardiomyocyte Culture and Myocardium Formation.

Harnessing biomaterials for in vitro tissue construction has long been a research focus because of its powerful potentials in tissue engineering and pharmaceutical industry. Myocardium is a critical cardiac tissue with complex multiple muscular layers. Considering the specific characters of native cardiac tissues, it is necessary to design a biocompatible and biomimetic platform for cardiomyocyte culture and myocardium formation with sustained physiological function. In this study, we developed gelatin-based hydrogels chemically cross-linked by genipin, a biocompatible cross-linker, as cell culture scaffolds. Moreover, to achieve and maintain the functionality of myocardium, for instance, well-organized cardiomyocytes and synchronized contractile behavior, we fabricated gelatin-based hydrogels with patterned microstructure using a microcontact printing technique. Furthermore, graphene oxide (GO), with unprecedented physical and chemical properties, has also been incorporated into gelatin for culturing cardiomyocytes. Our results show that micropatterned genipin-cross-linked gelatin hydrogels are very helpful to promote alignment and maturation of neonatal rat ventricular cardiomyocytes. More interestingly, the presence of GO significantly enhances the functional performance of cardiomyocytes, including an increase in contraction amplitude and cardiac gene expression. The cultured cardiomyocytes reach a well-synchronized contraction within 48 h of cell seeding and keep beating for up to 3 months. Our study provides a new and easy-to-use gelatin-based scaffold for improving physiological function of engineered cardiac tissues, exhibiting promising applications in cardiac tissue engineering and drug screening.

Synthesis and Characterization of Covalently Crosslinked pH-Responsive Hyaluronic Acid Nanogels: Effect of Synthesis Parameters.

Stable hyaluronic acid nanogels were obtained following the water-in-oil microemulsion method by covalent crosslinking with three biocompatible crosslinking agents: Divinyl sulfone, 1,4-butanediol diglycidyl ether (BDDE), and poly(ethylene glycol) bis(amine). All nanoparticles showed a pH-sensitive swelling behavior, according to the pKa value of hyaluronic acid, as a consequence of the ionization of the carboxylic moieties, as it was corroborated by zeta potential measurements. QELS studies were carried out to study the influence of the chemical structure of the crosslinking agents on the particle size of the obtained nanogels. In addition, the effect of the molecular weight of the biopolymer and the degree of crosslinking on the nanogels dimensions was also evaluated for BDDE crosslinked nanoparticles, which showed the highest pH-responsive response.

Direct 3D printing of monolithic ion exchange adsorbers

Monolithic adsorbers with anion exchange (AEX) properties have been 3D printed in an easy one-step process, i.e. not requiring post-functionalization to introduce the AEX ligands. The adsorber, 3D printed using a commercial digital light processing (DLP) printer, was obtained by copolymerisation of a bifunctional monomer bearing a positively charged quaternary amine as well as an acrylate group, with the biocompatible crosslinker polyethylene glycol diacrylate (PEGDA). To increase the surface area, polyethylene glycol was introduced into the material formulation as pore forming agent. The influence of photoinitiator (Omnirad 819) and photoabsorber (Reactive Orange 16, RO16) concentration was investigated in order to optimize printing resolution, allowing to reliably 3D print features as small as 200 μm and of highly complex Schoen Gyroids. Protein binding was measured on AEX adsorbers with a range of ligand densities (0.00, 2.03, 2.60 and 3.18 mmol/mL) using bovine serum albumin (BSA) and c-phycocyanin (CPC) as model proteins. The highest equilibrium binding capacity was found for the material presenting the lowest ligand density analysed (2.03 mmol/mL), adsorbing 73.7 ± 5.9 mg/mL and 38.0 ± 2.2 mg/mL of BSA and CPC, respectively. This novel 3D printed material displayed binding capacities in par or even higher than commercially available chromatographic resins. We expect that the herein presented approach of using bifunctional monomers, bearing commonly used chromatography ligands, will help overcome the material limitations currently refraining 3D printing applications in separation sciences.

Crosslinked chitosan films with controllable properties for commercial applications

In this research, sustainable and green bioproducts with controlled sorption and good mechanical properties have been developed from chitosan for commercial applications. Addition of citric acid, a biocompatible crosslinker, and later treating with alkali imparts excellent tensile strength and aqueous stability to the chitosan films. Films were developed from chitosan and studied for their sorption capabilities, mechanical properties, oxygen/water vapour transmission rates and antimicrobial abilities. Moisture sorption of up to 1466% based on the dry weight of chitosan was seen when the films were untreated. However, treating the films with alkali decreased their water sorption to 100–250% and made the films resistant even to boiling water. Modified chitosan could be moulded into various forms and made into bioproducts that could replace plastic based materials. The chitosan bioproducts developed have the potential to replace plastic based products and will help to provide a greener alternative for the plastic based commodity products in current use.

Beta-Glucan based temperature responsive hydrogels for 5-ASA delivery

A series of temperature responsive hydrogels consisting of (1,3)-(1,6) β-Glucan and poly (N-isopropyl acrylamide) (PNIPAM) was synthesized by redox polymerization at room temperature. Tetramethylethylenediamine (TEMED) and potassium persulfate (KPS) were used as a redox pair. β-glucan was methacrylated (MA-β-Glucan) and used as a biodegradable and bio-compatible cross-linker to prepare β-glucan-PNIPAM based temperature responsive hydrogels. Swelling behavior of the hydrogels at different temperatures was investigated. The 5-ASA release from the hydrogels was monitored using UV-VIS spectrophotometer at 37 °C. It is notable that, the swelling and release behaviors of the hydrogels significantly change depending on the hydrogel compositions and temperature. Their thermal stability was determined using thermogravimetric analysis (TGA), assuming the extent of intermolecular interaction between PNIPAM and β-glucan is proportional to thermal stability, which increased with the amount of PNIPAM. Volume phase transition temperature (VPTT) of the hydrogels was precisely determined by derivative differential scanning calorimeter (DDSC). They possessed variable VPTT with the compositions. The presence of β-glucan in the PNIPAM network brought VPTT closer to the body temperature (from 32.8 °C to 35.5 °C), indicating that the VPTT could be tuned by the hydrogel compositions. Their in-vivo biocompatibility was tested against WS1 human fibroblast cells in phosphate buffer saline (PBS, pH 7.4). It was demonstrated that, using MA-β-glucan as a cross-linker resulted in more bio-compatible thermo-responsive hydrogels indicating the enhancement of hydrophilic β-Glucan on the swollen hydrogel surface.

Gelatin — Oxidized carboxymethyl cellulose blend based tubular electrospun scaffold for vascular tissue engineering

The present work deals with the fabrication of electrospun tubular scaffold based on in-situ crosslinked blend of gelatin − oxidized carboxymethyl cellulose (OCMC) for vascular tissue engineering. The flow behavior and spinability of the hydrogel despite the in-situ crosslinked gelatin chains evaluated by Raman spectroscopic studies and rheological studies was utilized for electrospinning. The study highlights the tunable pore size and fiber diameter of the nanofibers with the manipulation of electrospinning parameters. With a future perspective of vascular tissue engineering, the electrospinning parameters yielding smooth bead free fibers and maximum magnitude in pore size and fiber diameter as well their homogenous distribution were selected for the fabrication of tubular constructs which is rarely reported. The surface and mechanical properties were evaluated to validate its properties to the native vessel. Biocompatibility was studied in vitro with BALB/c 3T3 cells and in vivo after subcutaneous implantation in rats. MTT assay confirmed its no-toxicity and no abnormal foreign body reaction were observed by 7 and 15days after implantation. Crosslinking with biocompatible crosslinker OCMC has rendered insolubility to gelatin yet making it spinable for electrospinning to fabricate porous, nanofibrous vascular biomaterial.

Self-Assembly Behavior and Biocompatible Cross-Linking of Double Hydrophilic Linear-Brush Block Copolymers.

The self-assembly of a novel double hydrophilic block copolymer (DHBC) architecture is presented. By combining linear biomacromolecule pullulan with biocompatible poly(oligo(ethylene glycol) methyl ether) methacrylate) (P(OEGMA))-brush blocks via copper(I) catalyzed azide alkyne cycloaddition, a novel DHBC linear-brush combination is obtained. Self-assembly in water was observed via optical microscopy and dynamic light scattering (DLS). Moreover, DLS investigations showed that self-assembly efficiency significantly relies on the degree of polymerization of the brush-block. Furthermore, the self-assembly of the formed particles was investigated with cryogenic scanning electron microscopy (cryo-SEM). To preserve the aggregates at lower concentrations, a biocompatible and FDA approved cross-linking agent, namely, sodium trimetaphosphate (STMP), was utilized for cross-linking. The reaction of STMP and pullulan was followed by 31P NMR, while the presence of the cross-linking agent within the particles could be detected via the combination cryo-SEM and energy dispersive X-ray spectroscopy.

Enhanced formation of hydroxyapatites in gelatin/imogolite macroporous hydrogels

HypothesisGelatin is widely investigated for the fabrication of synthetic scaffolds in bone tissue engineering. Practical limitations to its use are mainly due to the fast dissolution rate in physiological conditions and to the lack of pores with suitable dimensions for cell permeation. The aim of this work is to exploit imogolite clays as nucleation sites for the growth of calcium phosphates in gelatin-based hydrogels and to take advantage of a cryogenic treatment to obtain pores of ∼100µm. ExperimentsWe evaluated the effect of imogolites and a biocompatible cross-linker on the gelatin network in terms of morphology, thermal and rheological behavior. The hydrogels were cryogenically-treated and characterized to investigate the modification of the polymer network, both at the micro- and nano-scale. The samples were mineralized to investigate the effect of imogolites on the formation of calcium phosphates. FindingsThe interaction between gelatin, imogolite and cross-linker leads to the modification of the hydrogel structure at the micro-scale, while minor effects are detected at the nano-scale. The cryogenic procedure is successful in generating pores with the desired size, while the presence of imogolites in the hydrogel promotes hydroxyapatites formation. These results demonstrate that imogolites can be effectively employed as functional fillers in polymer-based scaffolds.

Humic acid particle embedded super porous gum Arabic cryogel network for versatile use

Super porous gum Arabic (GA) cryogels were synthesized by crosslinking of natural GA with divinyl sulfone at cryogenic conditions, −20°C for potential biomedical applications. Humic acid (HA) nanoparticles were also prepared by using degradable and biocompatible crosslinkers such as trimethylolpropane triglycidyl ether, poly(ethylene glycol) diglycidyl ether, and trisodium trimetaphosphate in a single step and then entrapped within GA cryogel network as GA/HA particle cryogel. Furthermore, GA/HA cryogel was used as a template for Ag, Cu, and Fe nanoparticle preparation, and their antimicrobial properties were tested against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis strains. The minimum inhibition concentration values of Ag and Cu nanoparticle‐loaded GA/HA cryogel composites were determined as 10 mg mL−1. Furthermore, the blood compatibility tests such as hemolysis and blood clotting indexes were determined for GA cryogels and found to be more compatible with 0.08 ± 0.01% hemolysis and 89.4 ± 6.1 blood clotting values, whereas the hemolysis of the Ag, Cu, and Fe nanoparticle‐loaded GA/HA Ag, Cu, and Fe metal nanoparticle cryogel composites decreased in the order of Fe > Cu > Ag nanoparticles.

Approximating bone ECM: Crosslinking directs individual and coupled osteoblast/osteoclast behavior.

Osteoblast and osteoclast communication (i.e. osteocoupling) is an intricate process, in which the biophysical profile of bone ECM is an aggregate product of their activities. While the effect of microenvironmental cues on osteoblast and osteoclast maturation has been resolved into individual variables (e.g. stiffness or topography), a single cue can be limited with regards to reflecting the full biophysical scope of natural bone ECM. Additionally, the natural modulation of bone ECM, which involves collagenous fibril and elastin crosslinking via lysyl oxidase, has yet to be reflected in current synthetic platforms. Here, we move beyond traditional substrates and use cell-derived ECM to examine individual and coupled osteoblast and osteoclast behavior on a physiological platform. Specifically, preosteoblast-derived ECM is crosslinked with genipin, a biocompatible crosslinker, to emulate physiological lysyl oxidase-mediated ECM crosslinking. We demonstrate that different concentrations of genipin yield changes to ECM density, stiffness, and roughness while retaining biocompatibility. By approximating various bone ECM profiles, we examine how individual and coupled osteoblast and osteoclast behavior are affected. Ultimately, we demonstrate an increase in osteoblast and osteoclast differentiation on compact and loose ECM, respectively, and identify ECM crosslinking density as an underlying force in osteocoupling behavior.

Inherently antioxidant and antimicrobial tannic acid release from poly(tannic acid) nanoparticles with controllable degradability

From a natural polyphenol, Tannic acid (TA), poly(TA) nanoparticles were readily prepared using a single step approach with three different biocompatible crosslinkers; trimethylolpropane triglycidyl ether (TMPGDE), poly(ethylene glycol) diglycidyl ether (PEGGE), and trisodium trimetaphosphate (STMP). P(TA) particles were obtained with controllable diameters between 400 to 800nm with −25mV surface charge. The effect of synthesis conditions, such as the emulsion medium, pH values of TA solution, and the type of crosslinker, on the shape, size, dispersity, yield, and degradability of poly(Tannic Acid) (p(TA)) nanoparticles was systematically investigated. The hydrolytic degradation amount in physiological pH conditions of 5.4, 7.4, and 9.0 at 37.5°C were found to be in the order TMPGDE<PEGGE<STMP. Furthermore, the degradation amounts of TA from p(TA) nanoparticles can be controlled by the appropriate choice of crosslinker, and the pH of releasing media. The highest TA release, 600mg/g, was obtained for TMPGDE-crosslinked p(TA) particles in intestinal pH conditions (pH 9) over 3 days; whereas, a slow and linear TA release profile over almost 30 days was obtained by using PEGGE-crosslinked p(TA) in body fluid pH conditions (pH 7.4). The total phenol content of p(TA) particles was calculated as 70±1μgmL−1 for 170μgmL−1 p(TA), and the trolox equivalent antioxidant capacity was found to be 2027±104mM trolox equivalent g−1. Moreover, p(TA) nanoparticles demonstrated strong antimicrobial effects against common bacterial strains. More interestingly, with a higher concentration of p(TA) particles, higher blood clotting indices were obtained.

Electrostatic Forces Mediated by Choline Dihydrogen Phosphate Stabilize Collagen

Cross-linkers aid in improving biostability of collagen via different mechanisms. Choline dihydrogen phosphate (cDHP), a biocompatible ionic liquid, has been reported as a potential cross-linker for collagen. However, its mechanism is yet unclear. This study explores the effect of cDHP on the physicochemical stability of collagen and nature of its interaction. Dielectric behavior of collagen-cDHP composites signifies that cDHP enhances intermolecular forces. This was demonstrated by an increase in cross-linked groups and high denaturation temperature of collagen-cDHP composites. XRD measurements reveal minor conformational change in helices. Molecular modeling studies illustrate that the force existing between collagen and cDHP is electrostatic in nature. Herein, it is postulated that dihydrogen phosphate anion attaches to cationic functional groups of collagen, resulting in closer vicinity of various side chains of collagen, forming physical and chemical cross-links within collagen, contributing to its structural stability. Our study suggests that dihydrogen phosphate anions can be employed for developing a new class of biocompatible cross-linkers.