Glutaraldehyde Cross-Linking of Oligolysines Coating DNA Origami Greatly Reduces Susceptibility to Nuclease Degradation.

DNA nanostructures (DNs) have garnered a large amount of interest as a potential therapeutic modality. However, DNs are prone to nuclease-mediated degradation and are unstable in low Mg2+ conditions; this greatly limits their utility in physiological settings. Previously, PEGylated oligolysines were found to protect DNs against low-salt denaturation and to increase nuclease resistance by up to ∼400-fold. Here we demonstrate that glutaraldehyde cross-linking of PEGylated oligolysine-coated DNs extends survival by up to another ∼250-fold to >48 h during incubation with 2600 times the physiological concentration of DNase I. DNA origami with cross-linked oligolysine coats are non-toxic and are internalized into cells more readily than non-cross-linked origami. Our strategy provides an off-the-shelf and generalizable method for protecting DNs in vivo.

Surface functionalized magnetic nanoparticles shift cell behavior with on/off magnetic fields.

Magnetic nanoparticles (MNPs) are used as contrast agents and targeted drug delivery systems (TDDS) due to their favorable size, surface charge, and magnetic properties. Unfortunately, the toxicity associated with MNPs limits their biological applications. Surface functionalization of MNPs with selective polymers alters the surface chemistry to impart better biocompatibility. We report the preparation of surface functionalized MNPs using iron oxide NPs (MNPs), poly (lactic-co-glycolic acid) (PLGA), and sodium alginate via co-precipitation, emulsification, and electro-spraying, respectively. The NPs are in the nanosize range and negatively charged. Morphological and structural analyses affirm the surface functionalized nanostructure of the NPs. The surface functionalized MNPs are biocompatible, and demonstrate enhanced intracellular delivery under an applied magnetic field (H), which evinces the targeting ability of MNPs. After NP treatment, the physico-mechanical properties of fibroblasts are decided by the selective MNP uptake under "on" or "off" magnetic field conditions. We envision potential use of biocompatible surface functionalized MNP for intracellular-, targeted-DDS, imaging, and for investigating cellular mechanics.

Biscarbamate cross-linked low molecular weight Polyethylenimine polycation as an efficient intra-cellular delivery cargo for cancer therapy.

BACKGROUND: A challenge in gene therapy is the efficient delivery of DNA/siRNA to the diseased cells. The physicochemical characteristics of siRNA, such as high molecular weight, negative charges and hydrophilic nature-prevent passive diffusion across the plasma membrane for most cells. A therapeutically feasible carrier for intra-cellular delivery of gene materials should accomplish a series of tasks such as: condensing nucleic acid, protecting nucleic acid from leaking in vivo, facilitating endosome escape and releasing DNA/siRNA to the target site. To meet these requirements, an efficient gene vector based on polycation synthesis for siRNA delivery both in vitro and in vivo was developed. RESULTS: The polymer was synthesized by 1, 4-butanediol bis (chloroformate) and PEI 800 Da to form PEI-Bu which could condense siRNA at the N/P ratio of 38.35 or above. The size of the nanoparticles was 100-300 nm and zeta potential was in the range of 10-30 mV at different N/P ratios. The nanoparticles can achieve the ability of cellular uptake and the silencing efficiency was about 46.63% in SMMC-7721 cell line which was generated to stably express GL3 luciferase gene. The cytotoxicity of the polyplex nanoparticles was almost negligible on SMMC-7721 cells by MTT assay, indicating that the reduced luciferase expression was the effect of RNAi, not the influence of cytotoxicity of polyplexes. The polyplex nanoparticle formulated by PEI-Bu and siRNA at N/P ratio of 115.05 was injected into the SMMC-7721 tumor bearing mice locally and the expression of luciferase can reduce to 63.17% compared with control group. CONCLUSIONS: Results in this study suggested that PEI-Bu polycation might provide a promising solution for siRNA delivery and had the potential in anti-tumor gene therapy.

A combination of in vitro comet assay and micronucleus test using human lymphoblastoid TK6 cells.

The comet assay has been widely used as a genotoxicity test for detecting primary DNA damage in individual cells. The micronucleus (MN) test is also a well-established assay for detecting clastogenicity and aneugenicity. A combination of the comet assay (COM) and MN test is capable of detecting a variety of genotoxic potentials as an in vitro screening system. Although the in vitro MN test has a robust protocol and Organisation for Economic Co-operation and Development (OECD) test guideline, the in vitro COM does not. To establish a robust protocol for the COM and to compare its sensitivity with that of the MN, we conducted COM and MN concurrently for five genotoxic agents (ethyl methanesulfonate, methyl methanesulfonate, hydrogen peroxide, gamma-rays and mitomycin C) and one non-genotoxic agent (triton X-100), using human lymphoblastoid TK6 cells. Relative cell count (RCC), relative population doubling (RPD), relative increase in cell count (RICC) and relative cell viability determined by trypan blue dye-exclusion assay (TBDE) were employed as cytotoxic measurements. However, the relative cell viability determined by TBDE just after the treatment was not an appropriate parameter of cytotoxicity for the genotoxic agents because it remained constant even at the highest doses, which showed severe cytotoxicity by RCC, RPD and RICC. The results of the COM showed qualitative agreement (positive or negative) with those of the MN except for mitomycin C, which is an interstrand cross-linker. The COM always required higher doses than the MN to detect the genotoxic potential of the genotoxic agents under the test conditions applied here. The doses that induced a comet tail always yielded <50% RICC, and do not accord to the OECD test guideline for MN because of their high cytotoxicity. These results are helpful for interpreting the results of the COM and MN in in vitro genotoxic hazard assessments. Further investigation is required to standardise the COM.

Block copolymer cross-linked nanoassemblies improve particle stability and biocompatibility of superparamagnetic iron oxide nanoparticles.

PURPOSE: To develop cross-linked nanoassemblies (CNAs) as carriers for superparamagnetic iron oxide nanoparticles (IONPs). METHODS: Ferric and ferrous ions were co-precipitated inside core-shell type nanoparticles prepared by cross-linking poly(ethylene glycol)-poly(aspartate) block copolymers to prepare CNAs entrapping Fe(3)O(4) IONPs (CNA-IONPs). Particle stability and biocompatibility of CNA-IONPs were characterized in comparison to citrate-coated Fe(3)O(4) IONPs (Citrate-IONPs). RESULTS: CNA-IONPs, approximately 30 nm in diameter, showed no precipitation in water, PBS, or a cell culture medium after 3 or 30 h, at 22, 37, and 43°C, and 1, 2.5, and 5 mg/mL, whereas Citrate-IONPs agglomerated rapidly (> 400 nm) in all aqueous media tested. No cytotoxicity was observed in a mouse brain endothelial-derived cell line (bEnd.3) exposed to CNA-IONPs up to 10 mg/mL for 30 h. Citrate-IONPs (> 0.05 mg/mL) reduced cell viability after 3 h. CNA-IONPs retained the superparamagnetic properties of entrapped IONPs, enhancing T2-weighted magnetic resonance images (MRI) at 0.02 mg/mL, and generating heat at a mild hyperthermic level (40 ~ 42°C) with an alternating magnetic field (AMF). CONCLUSION: Compared to citric acid coating, CNAs with a cross-linked anionic core improved particle stability and biocompatibility of IONPs, which would be beneficial for future MRI and AMF-induced remote hyperthermia applications.

In vitro toxicity assessment of crosslinking agents used in hyaluronic acid dermal filler.

Hyaluronic acid (HA) dermal fillers are produced by crosslinking HA with agents, such as 1,4-butanediol diglycidyl ether (BDDE) and poly (ethylene glycol) diglycidyl ether (PEGDE) to acquire desired properties. Thus, the safety evaluation of these crosslinkers is needed at the cellular level. In the present study, cell viability, cytotoxicity, membrane integrity, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and inflammatory responses were evaluated in the human keratinocyte cell line, HaCaT and human dermal fibroblast cell line, HDF in response to treatment with the crosslinkers. In both the cell lines, BDDE significantly decreased cell viability at 100-1000 ppm, while PEGDE showed a decrease at 500-1000 ppm. In HaCaT cells, BDDE markedly increased cytotoxicity (lactate dehydrogenase release) at 100-1000 ppm, but PEGDE showed an increase at 500-1000 ppm. Cells treated with BDDE (100 ppm) caused alteration in the integrity of cell membrane and shape. In both the cell lines, BDDE-treated cells showed significantly higher ROS levels and MMP loss than PEGDE-treated cells. Also, BDDE-treated cells exhibited higher COX-2 expression at 100 ppm. Expression of inflammatory cytokines (TNF-α, and IL-1 ß) was higher in BDDE-treated cells. Taken together, PEGDE-treated cells showed markedly lower cytotoxicity, ROS production, and inflammatory responses than BDDE-treated cells. Our data suggest that PEGDE is safer than BDDE as a crosslinker in HA dermal fillers.

Stretchable and Bioadhesive Gelatin Methacryloyl-Based Hydrogels Enabled by in Situ Dopamine Polymerization.

Hydrogel patches with high toughness, stretchability, and adhesive properties are critical to healthcare applications including wound dressings and wearable devices. Gelatin methacryloyl (GelMA) provides a highly biocompatible and accessible hydrogel platform. However, low tissue adhesion and poor mechanical properties of cross-linked GelMA patches (i.e., brittleness and low stretchability) have been major obstacles to their application for sealing and repair of wounds. Here, we show that adding dopamine (DA) moieties in larger quantities than those of conjugated counterparts to the GelMA prepolymer solution followed by alkaline DA oxidation could result in robust mechanical and adhesive properties in GelMA-based hydrogels. In this way, cross-linked patches with ∼140% stretchability and ∼19 000 J/m3 toughness, which correspond to ∼5.7 and ∼3.3× improvement, respectively, compared to that of GelMA controls, were obtained. The DA oxidization in the prepolymer solution was found to play an important role in activating adhesive properties of cross-linked GelMA patches (∼4.0 and ∼6.9× increase in adhesion force under tensile and shear modes, respectively) due to the presence of reactive oxidized quinone species. We further conducted a parametric study on the factors such as UV light parameters, the photoinitiator type (i.e., lithium phenyl-2,4,6-trimethylbenzoylphosphinate, LAP, versus 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, Irgacure 2959), and alkaline DA oxidation to tune the cross-linking density and thereby hydrogel compliance for better adhesive properties. The superior adhesion performance of the resulting hydrogel along with in vitro cytocompatibility demonstrated its potential for use in skin-attachable substrates.

Single intratracheal administration of cross-linked water-soluble acrylic acid polymer causes acute alveolo-interstitial inflammation and the subsequent fibrotic formation possibly via the TGF-ß1 pathway in the lung of rats.

In a Japanese chemical factory, a lung disease like pneumoconiosis appeared at a high rate among workers handling cross-linked water-soluble acrylic acid polymer (CWAAP). To our knowledge, no such case was known in the world until very recently. The present study was designed to elucidate the effect of single intratracheal CWAAP instillation on the lung of rats. The CWAAP group had a significant increase in relative lung weight accompanied by a significant elevation in the number of total cells, total protein concentrations, and myeloperoxidase concentrations in bronchoalveolar lavage fluid when compared to the control group. The histopathological study revealed acute lung inflammation with the destruction of alveoli. The factors promoting fibrosis, macrophages, TGF-ß1, collagen and fibronectin vs. the factors suppressing fibrosis, matrix metalloproteinases were more powerfully driven in the CWAAP group, resultantly leading to fibrotic formation. In turn, we examined if acute lung inflammation and the subsequent fibrotic formation seen in the CWAAP group appeared in the other water-soluble polymer groups. Their histopathological findings were observed only in the polyacrylic acid sodium (PAAS), a monomer of CWAAP, group. The degree of inflammation and fibrogenesis was stronger in the CWAAP group than in the PAAS group. In conclusion, the present study demonstrated the induction of acute lung inflammation and the subsequent fibrotic formation by single intratracheal CWAAP instillation. The structural features of CWAAP that contains many carboxyl groups and cross-linked chains may be responsible for enhanced inflammation and fibrogenesis in the lung.

Mitigation of calcification and cytotoxicity of a glutaraldehyde-preserved bovine pericardial matrix: improved biocompatibility after extended implantation in the subcutaneous rat model.

BACKGROUND AND AIMS OF THE STUDY: Implanted non-crosslinked tissues suffer rapid degeneration, shrinkage and absorption, whereas standard crosslinked tissues cause local cytotoxicity and calcification. Both approaches diminish implant capacity for long-term function. The study aim was to examine the tissue-engineered characteristics (cytotoxicity, calcification potential, biocompatibility) of bovine pericardium, crosslinked with a low concentration of glutaraldehyde (GA) followed by ADAPT anti-mineralization, following prolonged implantation in a subcutaneous rat model. METHODS: Bovine pericardium was decellularized with Triton X-100, deoxycholate, IgePal CA-630, and nucleases. The resulting matrices were allocated to: group I (control, n=10), crosslinked in 0.2% polymeric GA; and group II (treatment, n=10), crosslinked in 0.05% monomeric GA + ADAPT. Cytotoxicity was determined by in vitro cell seeding with human fibroblasts, and quantified using an Alamar Blue assay. The matrices were then implanted in a subcutaneous rat model and retrieved after extended implantation times (26 and 52 weeks). This was followed by further histology, immunohistochemical staining, and measurement of calcium deposition. RESULTS: Complete acellularity and biostability were significantly (p < 0.01) achieved in group II. Inflammatory responses were reduced and beneficial host cell infiltration with neocapillary formation was limited to group II. Fibroblast infiltration was significantly increased from six to 12 months' implantation time. Only group II tested positive for Factor VIII and vimentin. After 52 weeks, extractable calcium levels were significantly (p < 0.001) reduced in group II (2.56 +/- 0.22 microg Ca/mg tissue) compared to group I (136.02 +/- 0.39 microg Ca/mg tissue). CONCLUSION: Acellular bovine pericardium, when crosslinked with a low concentration of GA and treated with ADAPT, retains and improves its integrity with a low immunoreactivity over a prolonged period. Host cell infiltration is also optimized over time. The maintenance of reduced calcification levels in group II suggests that such a biomaterial might have an advanced long-term in vivo potential.

Ferrous sulfate-directed dual-cross-linked hyaluronic acid hydrogels with long-term delivery of donepezil.

Ferrous sulfate (FeSO4)-directed dual-cross-linked hydrogels were designed for application in single-syringe injections. The use of FeSO4, rather than other iron salts, can modulate the gelation time and make it available for subcutaneous injection with a single syringe. These hydrogels are based on hyaluronic acid-dopamine (HA-dp) that contain donepezil (DPZ)-entrapping poly(lactic-co-glycolic acid) (PLGA) microsphere (MS). Although DPZ has been administered orally, its sustained release formulation via subcutaneous injection may reduce the dosing frequency for patients with Alzheimer's disease. The HA-dp conjugate was synthesized via an amide bond reaction for coordination of dp with a metal ion (Fe2+ or Fe3+) and self-polymerization of dp. The HA-dp/DPZ-loaded PLGA MS (PD MS)/FeSO4 gel system was considerably hardened via both the coordination of the metal ion with HA-dp and covalent bonding of dp. In addition, a quick restoration of the collapsed gel structure and sustained DPZ release from the HA-dp/PD MS/FeSO4 structure were achieved. The pharmacokinetic parameters after its subcutaneous injection in a rat indicate the sustained release and absorption of DPZ from the HA-dp/PD MS/FeSO4 system. The proposed system can be prepared by a simple method and can be efficiently and safely used for the long-term delivery of DPZ after the subcutaneous injection.

Evaluation of the Effect of Crosslinking Method of Poly(Vinyl Alcohol) Hydrogels on Thrombogenicity.

PURPOSE: Crosslinked poly(vinyl alcohol) (PVA) is a biomaterial that can be used for multiple cardiovascular applications. The success of implanted biomaterials is contingent on the properties of the material. A crucial consideration for blood-contacting devices is their potential to incite thrombus formation, which is dependent on the material surface properties. The goal of this study was to quantify the effect of different crosslinking methods of PVA hydrogels on in vitro thrombogenicity. METHODS: PVA was manufactured using three different crosslinking methods: 30% sodium trimetaphosphate (STMP), three 24 h freeze-thaw cycles (FT), and 2% glutaraldehyde-crosslinked (GA) to produce STMP-PVA, FT-PVA and GA-PVA, respectively. Expanded polytetrafluoroethylene (ePTFE) was used as a clinical control. As markers of thrombus formation, the degree of coagulation factor (F) XII activation, fibrin formation, and platelet adhesion were measured. RESULTS: The GA-PVA material increased FXII activation in the presence of cofactors compared to vehicle and increase platelet adhesion compared to other PVA surfaces. The STMP-PVA and FT-PVA materials had equivalent degrees of FXII activation, fibrin formation and platelet adhesion. CONCLUSION: This work supports crosslinker dependent thrombogenicity of PVA hydrogels and advances our understanding of how the manufacturing of a PVA hydrogel affects its hemocompatibility.

PEDOT:PSS interfaces stabilised using a PEGylated crosslinker yield improved conductivity and biocompatibility.

The rapidly expanding fields of bioelectronics, and biological interfaces with electronic sensors and stimulators, are placing an increasing demand on candidate materials to serve as robust surfaces that are both biocompatible, stable and electroconductive. Amongst conductive polymers, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a promising material in biomedical research due to its appropriate stability and high conductivity, however its intrinsic solubility requires a crosslinking process that can limit its conductivity and biocompatibility. Poly(ethylene glycol) is known to be a suitably anti-immunogenic moiety and its derivatives have been widely used for biomedical applications. In this study we investigate the application of poly(ethylene glycol)diglycidyl ether (PEGDE) as an effective crosslinker and conductive filler for PEDOT:PSS. From our interpretation of XPS analysis we hypothesise that the crosslinking reaction is occurring via the epoxy ring of PEGDE interacting with the sulfonic groups of excel PSS chains, which reaches a saturation at 3 w/v% PEGDE concentration. PEGDE crosslinked films did not disperse in aqueous environments, had enhanced electrical conductivity and imparted a significant degree of hydrophilicity to PEDOT:PSS films. This hydrophilicity and the presence of biocompatible PEGDE led to good cell viability and a significantly increased degree of cell spreading on PEDOT:PSS films. In comparison to widely reported chemical crosslinking via glycidoxy propyltrimethoxysilane (GOPS), this original crosslinking yields a highly hydrophilic 2D film substrate with increased electroconductive and biocompatibility properties, resulting in a next-generation formulation for bioengineering applications.

Pullulan dialdehyde crosslinked gelatin hydrogels with high strength for biomedical applications.

Herein the construction of a strong gelatin hydrogel is presented by using pullulan dialdehyde (PDA) as a macromolecular crosslinker. The resultant PDA crosslinked gelatin hydrogels (G-PDA) exhibit extremely high mechanical strength, manifested in the achieved optimal compressive stress of 5.80 MPa at 80% strain, which is up to 152 times higher than pure gelatin hydrogel. The G-PDA were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The extent of crosslinking was determined by ninhydrin assay. The results suggested that the synergistic effect of dual-crosslinking, which is composed of short- and long-range covalent crosslinking and thermoreversible physical crosslinking, may played a key role in enhancing the load-bearing capacity of ensuing hydrogels. The swelling and enzymatic degradation of G-PDA are gradually limited with increasing PDA concentration. The result from MTT assay demonstrated that G-PDA is non-cytotoxic against MC3T3 cells, regardless of the concentrations of PDA.

The effect of hydrazide linkers on hyaluronan hydrazone hydrogels.

The effect of hydrazide linkers on the formation and mechanical properties of hyaluronan hydrogels was intensively evaluated. The reaction kinetics of hydrazone formation was monitored by NMR spectroscopy under physiological conditions where polyaldehyde hyaluronan (unsaturated: ΔHA-CHO, saturated: HA-CHO) was reacted with various hydrazides to form hydrogels. Linear (adipic, oxalic dihydrazide) and branched (N,N´,N´´-tris(hexanoylhydrazide-6-yl)phosphoric triamide and 4-arm-PEG hydrazide) hydrazides were compared as crosslinking agents. The mechanical properties of hydrogels were also modified by attaching a hydrophobic chain to HA-CHO; however, it was found that this modification did not lead to an increase in hydrogel stiffness. Cytotoxicity tests showed that all tested hydrazide crosslinkers reduced the viability of cells only slightly, and that the final hyaluronan hydrogels were non-toxic materials.

Biocompatible dialdehyde cellulose/poly(vinyl alcohol) hydrogels with tunable properties.

Solubilized dialdehyde cellulose (DAC), an efficient crosslinking agent for poly(vinyl alcohol) (PVA), provides less toxic alternative to current synthetic crosslinking agents such as glutaraldehyde, while simultaneously allowing for the preparation of hydrogels with comparably better characteristics. PVA/DAC hydrogels prepared using 0.5, 1 and 1.5 wt% of DAC were analyzed in terms of mechanical, swelling and cytotoxicity characteristics. Materials properties of PVA/DAC hydrogels range from stiff substances to soft viscoelastic gels capable of holding large amounts of water. Superior mechanical properties, porosity and surface area in comparison with analogical PVA/glutaraldehyde hydrogels were observed. Biological studies showed low toxicity and good biocompatibility of PVA/DAC hydrogels. Potential of PVA/DAC in mesh-controlled release of biologically active compounds was investigated using ibuprofen, rutin and phenanthriplatin. Hydrogel loaded with anticancer drug phenantriplatin was found effective against alveolar cancer cell line A549 under in vitro conditions.

Cytotoxicity of silica-glass fiber reinforced composites.

OBJECTIVES: Silica-glass fiber reinforced polymers can be used for many kinds of dental applications. The fiber reinforcement enhances the mechanical properties of the polymers, and they have good esthetic attributes. There is good initial bonding of glass fibers to polymers via an interface made from silane coupling agents. The aim of this in vitro study was to determine the cytotoxicity of two polymers reinforced with two differently sized silica-glass fibers before and after thermal cycling. Cytotoxicity of the polymers without fibers was also evaluated. METHODS: Two different resin mixtures (A and B) were prepared from poly(vinyl chloridecovinylacetate) powder and poly(methyl methacrylate) (PMMA) dissolved in methyl methacrylate and mixed with different cross-linking agents. The resin A contained the cross-linking agents ethylene glycol dimethacrylate and 1,4-butanediol dimethacrylate, and for resin B diethylene glycol dimethacrylate was used. Woven silica-glass fibers were used for reinforcement. The fibers were sized with either linear poly(butyl methacrylate)-sizing or cross-linking PMMA-sizing. Cytotoxicity was evaluated by filter diffusion test (ISO 7405:1997) of newly made and thermocycled test specimens. Extracts were prepared according to ISO 10993-12 from newly made and from thermocycled specimens and tested by the MTT assay. The results from the experiments were statistically analyzed by one-way ANOVA and Tukey's test (rho<0.05). RESULTS: The filter diffusion test disclosed no change in staining intensity at the cell-test sample contact area indicating non-cytotoxicity in all experimental groups. Cell viability assessed by MTT assay was more than 90% in all experimental groups. All are non-cytotoxic. SIGNIFICANCE: It can be concluded that correctly processed heat polymerized silica-glass fiber reinforced polymers induced no cytotoxicity and that thermocycling did not alter this property.

Ethylene glycol dimethacrylate and diethylene glycol dimethacrylate exhibits cytotoxic and genotoxic effect on human gingival fibroblasts via induction of reactive oxygen species.

Although methacrylic acid derivatives in their polymeric form are considered to be safe, insufficient polymerization and the release of monomers due to either mechanical or enzymatical factors can lead to their reaching millimolar concentrations in local tissue. The present study evaluates the effect of two methacrylate monomers - ethylene glycol dimethacrylate (EGDMA) and diethylene glycol dimethacrylate (DEGDMA) - on human gingival fibroblasts (HGFs). Both monomers were found to reduce cells viability in MTT assay, increase apoptosis and cause cell cycle arrest in G1/G0 phase. They also increased intracellular reactive oxygen species (ROS) production as measured by DCFH-DA and DHE probes and increased expression of GPx4 and SOD2. Both monomers increased DNA damage in comet assay. Moreover, HGFs were not able to repair those lesions within 120min of repair incubation. However, the monomers were not found to have any effect on the integrity of isolated plasmids. We postulate that EGDMA and DEGDMA exhibit their cytotoxic and genotoxic properties via increased production of ROS, which cause DNA damage, affect apoptosis, viability and cell cycle. Further studies are needed to better understand the properties of methacrylic acid monomers and to evaluate the risk that they cause for patients, dentists and dental technicians.

Fabrication of photo-crosslinkable glycol chitosan hydrogel as a tissue adhesive.

In this work, an in situ gelling system composed of glycol chitosan (GC) was fabricated and evaluated regarding its tissue-adhesive, anti-bacterial and hemostatic properties. GC conjugated with 3-(4-hydroxyphenyl) propionic acid gelled immediately after illumination with blue light in the presence of ruthenium complex. The phenolic GC hydrogel was investigated regarding its mechanical property, hydration, degradation rate, cytotoxicity, tissue adhesiveness, and hemostatic ability. The hydrogel was shown to glue two pieces of tissues tightly in an egg-membrane model. The antibiotic-incorporated hydrogel killed bacteria effectively. When the hydrogel was applied to a wound in a mouse liver model, bleeding was reduced quickly and greatly. All the promising results show that the photo-chemically crosslinkable GC hydrogel could be used as a tissue adhesive, controlled drug release, and a hemostat.

Biofabrication of genipin-crosslinked peptide hydrogels and their use in the controlled delivery of naproxen.

The synthesis and optimization of peptide-based hydrogel materials have gained growing interest in the last years, thanks to their properties, that make them appealing for diverse biotechnological applications, with a particular focus in the field of biomedicine. The self-assembling abilities of low molecular weight peptides make them ideal for designing advanced materials using mild reaction conditions. In this work, a biocatalytic approach has been used for the synthesis of an Fmoc-tripeptide that is able to self-assemble in water affording a self-supporting hydrogel. The mechanical properties of this material have been enhanced through chemical crosslinking by using a natural compound, genipin, that allows to minimize cytotoxic effects. Moreover, we have tested the potential of the prepared materials to be employed as drug delivery systems using naproxen as an anti-inflammatory model drug, and studying its release kinetics in aqueous medium. The cytotoxicity of the hydrogels has been evaluated, and their mechanical and morphological properties have been studied by rheology and SEM microscopy.

Synthesis and characterization of a new photo-crosslinkable glycol chitosan thermogel for biomedical applications.

The major limitations of typical thermogelling polymers for practical applications are low gel stability and weak mechanical properties under physiological conditions. In this study, we have synthesized a new polysaccharide-based thermogelling polymer that can be photo-crosslinked by UV irradiation to form a mechanically resilient and elastic hydrogel. Methacrylated hexanoyl glycol chitosan (M-HGC), was synthesized by a series of chemical modifications, N-hexanoylation and N-methacrylation, of glycol chitosan (GC). Various M-HGC polymers with different methacryl group contents were synthesized and their thermogelling and photo-crosslinkable properties were evaluated. The M-HGCs demonstrated a thermo-reversible sol-gel transition behavior in aqueous solutions. The thermally-induced hydrogels could be chemically crosslinked by UV-triggered photo-crosslinking. From the cytotoxicity studies using MTT and the live/dead assay, the M-HGC hydrogels showed non-cytotoxicity. These photo-crosslinkable thermogelling M-HGC polymers may hold great promises for various biomedical applications, such as an injectable delivery system and 3D cell culture.