The synthesis of a physically crosslinked NVP based hydrogel

Controlled synthesis of ternary acrylamide/sodium acrylate/polyethyleneglycol hybrids by integrating different clays and fillers: a comprehensive evaluation of structural features

A series of anionic poly(acrylamide-co-sodium acrylate)/poly(ethylene glycol), PAN/PEG, hybrids were conveniently synthesized via free radical aqueous polymerization by integrating bentonite, kaolin, mica, graphene and silica, following a simple and eco-friendly crosslinking methodology. A comparative perspective was presented on how integrated nanofillers affect the physicochemical properties of hybrid gels depending on the differences in their structures. Among the five types of nanofillers, bentonite-integrated hybrid gel had the highest water absorbency, while graphene-integrated gel had the lowest. The elastic moduli of hybrid gels with the same content of inorganic component followed the order graphene > silica > mica > kaolin > bentonite. Adding 1.50% (w/v) bentonite to the PAN/PEG matrix increased the elastic modulus by 1.4 times compared to the as-prepared state, while adding the same amount of graphene created a 4.1-fold increase. By decreasing the synthesis temperature of hybrids to cryoconditions, -18 °C, an increase in the modulus of all gels was observed, while the modulus of graphene-doped gels increased from 25.9 kPa to 39.1 kPa. pH-dependent swelling demonstrated that hybrid gels can dynamically bind or release protons in response to changes in surrounding pH and thus abruptly change their overall dimensions. On-off switching behavior as reversible pulsatile swelling in pH 11.2 and deswelling in pH 2.1 showed that hybrid gels exhibit reversible pH-responsiveness following Fickian diffusion of water into the hybrid matrix. The change in pH of the swelling medium caused a 4.5-fold increase in swelling ratio for the silica-doped hybrid gels. The studies in which anionic hybrids were tested to explore adsorption potential for cationic dye methylene blue (MB) showed that adsorbent properties could be tuned to the desired extent by incorporating different fillers. In terms of efficiency among the selected fillers, the maximum efficiency for MB was obtained as 99.2% and 88.60% for hybrids containing graphene and silica, respectively. The adsorption of MB on hybrids was fit to the three-parameter Sips model rather than the two-parameter models. The results introduced a new perspective on the design of ternary hybrid gels that could effectively address both the mechanical and responsive properties of soft materials, providing a platform for subsequent cationic dye adsorption.

Gamma Radiation-Induced Synthesis of Carboxymethyl Cellulose-Acrylic Acid Hydrogels for Methylene Blue Dye Removal

This study aims to develop efficient and sustainable hydrogels for dye adsorption, addressing the critical need for improved wastewater treatment methods. Carboxymethyl cellulose (CMC)-based hydrogels grafted with AAc were synthesized using gamma radiation polymerization. Various AAc to CMC ratios (5:5, 5:7.5, 5:10, 5:15) were treated with 37% NaOH and exposed to 1-15 kGy radiation, with the optimal hydrogel obtained at 5 kGy. Swelling studies showed an increase in swelling with 5-7.5% AAc content, with the 5:7.5 hydrogel achieving the highest swelling at 18,774.60 (g/g). FTIR spectroscopy confirmed the interaction between AAc and CMC, indicating the successful formation of the hydrogel. DSC analysis revealed that higher AAc content led to increased glass transition and decomposition temperatures, thereby enhancing thermal stability. The swelling kinetics were linked to a reduction in pore size and improved AAc grafting. The 5:7.5 hydrogel demonstrated the highest adsorption capacity (681 mg/g) for methylene blue at 80 mg/L, achieving a desorption efficiency of 95% in 2M HCl. Kinetic analysis revealed non-uniform physisorption on a heterogeneous surface, which followed Schott's pseudo-second-order model. This study advances the development of efficient hydrogels for water purification, providing a cost-effective and environmentally friendly solution for large-scale applications.

Water-Absorbing Bioadhesive Poly(Acrylic Acid)/Polyvinylpyrrolidone Complex Sponge for Hemostatic Agents

BACKGROUND

Poly(acrylic acid) (PAA) is a water-soluble synthetic polymer with tissue-adhesive properties. When PAA is mixed with polyvinylpyrrolidone (PVP) in water, it forms a water-insoluble precipitate that neither swells nor adheres to tissues.

METHODS AND RESULTS

We developed a novel solid/solution interface complexation method to obtain a water-swellable PAA/PVP complex. First, PAA solution was dried up in a vessel to form a film. The PAA film was then immersed in an aqueous PVP solution to obtain a highly swollen PAA/PVP hydrogel. Heat drying of the hydrogel yielded a transparent film, while freeze-drying the hydrogel provided a soft sponge. Both the PAA/PVP film and sponge could be re-swelled by water to obtain a bioadhesive gel. A relatively larger specific surface area of the sponge than that of the film led to a more rapid swelling and water absorption behavior and quick adhesion to tissues. The addition of hyaluronic acid (HA) improved the mechanical characteristics of the sponges. PAA/PVP/HA sponges had low cytotoxicity, and they exhibited high hemostatic efficiency in clinical studies after dialysis treatment or tooth extraction, even in patients on antithrombotic drugs.

CONCLUSIONS

Such bioadhesive materials consisting of low-toxicity polymers have a high potential for use in medical hemostatic devices.

Polyurethanes Crosslinked with Poly(vinyl alcohol) as a Slowly-Degradable and Hydrophilic Materials of Potential Use in Regenerative Medicine

Novel, slowly-degradable and hydrophilic materials with proper mechanical properties and surface characteristics are in great demand within the biomedical field. In this paper, the design, synthesis, and characterization of polyurethanes (PUR) crosslinked with poly(vinyl alcohol) (PVA) as a new proposition for regenerative medicine is described. PVA-crosslinked PURs were synthesized by a two-step polymerization performed in a solvent (dimethylsulfoxide, DMSO). The raw materials used for the synthesis of PVA-crosslinked PURs were poly(ε-caprolactone) (PCL), 1,6-hexamethylene diisocyanate (HDI), and PVA as a crosslinking agent. The obtained materials were studied towards their physicochemical, mechanical, and biological performance. The tests revealed contact angle of the materials surface between 38-47° and tensile strength in the range of 41-52 MPa. Mechanical characteristics of the obtained PURs was close to the characteristics of native human bone such as the cortical bone (TSb = 51-151 MPa) or the cancellous bone (TSb = 10-20 MPa). The obtained PVA-crosslinked PURs did not show significant progress of degradation after 3 months of incubation in a phosphate-buffered saline (PBS). Accordingly, the obtained materials may behave similar to slowly-degradable materials, which can provide long-term physical support in, for example, tissue regeneration, as well as providing a uniform calcium deposition on the material surface, which may influence, for example, bone restoration. A performed short-term hemocompatibility study showed that obtained PVA-crosslinked PURs do not significantly influence blood components, and a cytotoxicity test performed with the use of MG 63 cell line revealed the great cytocompatibility of the obtained materials. According to the performed studies, such PVA-crosslinked PURs may be a suitable proposition for the field of tissue engineering in regenerative medicine.

Controlling fungal biofilms with functional drug delivery denture biomaterials

Candida-associated denture stomatitis (CADS), caused by colonization and biofilm-formation of Candida species on denture surfaces, is a significant clinical concern. We show here that modification of conventional denture materials with functional groups can significantly increase drug binding capacity and control drug release rate of the resulting denture materials for potentially managing CADS. In our approach, poly(methyl methacrylate) (PMMA)-based denture resins were surface grafted with three kinds of polymers, poly(1-vinyl-2-pyrrolidinone) (PNVP), poly(methacrylic acid) (PMAA), and poly(2-hydroxyethyl methacrylate) (PHEMA), through plasma-initiated grafting polymerization. With a grafting yield as low as 2 wt%, the three classes of new functionalized denture materials showed significantly higher drug binding capacities toward miconazole, a widely used antifungal drug, than the original PMMA denture resin control, leading to sustained drug release and potent biofilm-controlling effects against Candida. Among the three classes of functionalized denture materials, PNVP-grafted resin provided the highest miconazole binding capability and the most powerful antifungal and biofilm-controlling activities. Drug binding mechanisms were studied. These results demonstrated the importance of specific interactions between drug molecules and functional groups on biomaterials, shedding lights on future design of CADS-managing denture materials and other related devices for controlled drug delivery.

Synthesis of a novel pH responsive phyllosilicate loaded polymeric hydrogel based on poly(acrylic acid-co-N-vinylpyrrolidone) and polyethylene glycol for drug delivery: modelling and kinetics study for the sustained release of an antibiotic drug

In this study, we developed a novel pH-sensitive composite interpenetrating polymeric network (IPN) hydrogel based on polyethylene gylcol (PEG) and poly(acrylic acid-co-N-vinylpyrrolidone) crosslinked with N,N-methylenebisacrylamide (MBA).

Preparation and characterization of keratin-based biocomposite hydrogels prepared by electron beam irradiation

The biocompatible and highly porous keratin-based hydrogels were prepared using electron beam irradiation (EBI). The conditions for keratin-based hydrogel formation were investigated depending on several conditions, including the presence of poly(vinyl alcohol) (PVA), concentration of keratin solution, EBI dose, and poly(ethylene imine) (PEI) additives. The pure keratin (human hair and wool) aqueous solution was not gelled by EBI, while the aqueous keratin solutions blended with PVA were gelled at an EBI dose of more than 90 kGy. Furthermore, in the presence of PEI, the aqueous keratin solution blended with PVA could be gelled at a considerably lower EBI dose, even at 10 kGy. This finding suggests that the PEI additives significantly influence the rate of gelation and that PEIs function as an accelerator during gelation. The resulting keratin-based hydrogels were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), gel fraction, degree of swelling, gel strength, and kinetics of swelling analyses.

Preparation of a hyaluronic acid hydrogel through polyion complex formation using cationic polylactide-based microspheres as a biodegradable cross-linking agent

A novel hyaluronic acid (HA)-based hydrogel was prepared through polyion complex (PIC) formation between cationic polylactide (PLA)-based microspheres (MS+) and hyaluronic acid (HA-) as an anionic polyelectrolyte. The MS+ and HA formed a biodegradable PIC hydrogel (HA-/MS+) when mixed in aqueous media. The swelling behavior and mechanical properties of the PIC hydrogel could be controlled by changing the charge ratio between HA- and MS+. In addition, the HA-/MS+ PIC hydrogel resulted in a lower inflammatory response compared with a collagen hydrogel in vivo.

Cyto- and genotoxicological assessment and functional characterization of N-vinyl-2-pyrrolidone-acrylic acid-based copolymeric hydrogels with potential for future use in wound healing applications

This study investigated the toxicity of N-vinyl-2-pyrrolidone-acrylic acid copolymer hydrogels crosslinked with ethylene glycol dimethacrylate or poly(ethylene glycol) dimethacrylate. There is a pressing need to establish the toxicity status of these new copolymers because they may find applications in future wound healing processes. Investigations revealed that the capacity of these hydrogels for swelling permitted the retention of high amounts of water yet still maintaining structural integrity. Reverse phase HPLC analysis suggested that unreacted monomeric base material was efficiently removed post-polymerization by applying an additional purification process. Subsequently, in vitro toxicity testing was performed utilizing direct and indirect contact exposure of the polymers to human keratinocytes (HaCaT) and human hepatoma (HepG2) cells. No indication of significant cell death was observed using the established MTT, neutral red (NR) and fluorescence-based toxicity endpoint indicators. In addition, the alkaline Comet assay showed no genotoxic effects following cell exposure to hydrogel extracts. Investigations at the nucleotide level using the Ames mutagenicity assay demonstrated no evidence of mutagenic activity associated with the polymers. Findings from this study demonstrated that these hydrogels are non-cytotoxic and further work can be carried out to investigate their potential as a wound-healing device that will impact positively on patient health and well-being.

Injectable Poly(ethylene glycol) Dimethacrylate-based Hydrogels with Hydroxyapatite

Injectable hydrogels are attractive materials for tissue engineering as they provide fast reaction rates, low heat release, and biocompatibility for cell proliferation and permanent interface with surrounding tissue. A series of injectable poly(ethylene glycol) dimethacrylate (PEGDMA) hydrogels with four different weight fractions of hydroxyapatite (HA) particles were prepared and thermal and mechanical properties evaluated. The cytocompatibility was assessed by examining the viability and morphology of human mesenchymal stem cells (hMSCs) seeded on the hydrogels. The in situ crosslink process displayed a vast decrease in the maximal temperature and an increase in the maximal temperature time. Cytocompatibility evaluation by MTT assay, scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) showed that the cells on the composite hydrogels possessed better viability and adherence than the hydrogels without HA. The results indicated that composite hydrogels have potential as injectable materials for tissue engineering application.

Synthesis of a proline-modified acrylic acid copolymer in supercritical CO2 for glass-ionomer dental cement applications

Supercritical (sc-) fluids (such as sc-CO(2)) represent interesting media for the synthesis of polymers in dental and biomedical applications. Sc-CO(2) has several advantages for polymerization reactions in comparison to conventional organic solvents. It has several advantages in comparison to conventional polymerization solvents, such as enhanced kinetics, being less harmful to the environment and simplified solvent removal process. In our previous work, we synthesized poly(acrylic acid-co-itaconic acid-co-N-vinylpyrrolidone) (PAA-IA-NVP) terpolymers in a supercritical CO(2)/methanol mixture for applications in glass-ionomer dental cements. In this study, proline-containing acrylic acid copolymers were synthesized, in a supercritical CO(2) mixture or in water. Subsequently, the synthesized polymers were used in commercially available glass-ionomer cement formulations (Fuji IX commercial GIC). Mechanical strength (compressive strength (CS), diametral tensile strength (DTS) and biaxial flexural strength (BFS)) and handling properties (working and setting time) of the resulting modified cements were evaluated. It was found that the polymerization reaction in an sc-CO(2)/methanol mixture was significantly faster than the corresponding polymerization reaction in water and the purification procedures were simpler for the former. Furthermore, glass-ionomer cement samples made from the terpolymer prepared in sc-CO(2)/methanol exhibited higher CS and DTS and comparable BFS compared to the same polymer synthesized in water. The working properties of glass-ionomer formulations made in sc-CO(2)/methanol were comparable and better than the values of those for polymers synthesized in water.

Molecular structure of physiologically-responsive hydrogels controls diffusive behavior

Polymeric networks and the ensuing hydrogels of MAA and NVP were successfully synthesized using a UV-initiated free radical polymerization and characterized to assess their applicability as carriers for directed drug delivery. FT-IR spectroscopy revealed shifts in peak absorbances that indicated the presence of hydrogen bonding complexes between functional groups, while SEM imaging showed that the different comonomers affect the surface morphology of the microparticles. Dynamic pH swelling studies demonstrated the pH responsiveness of the carriers in gastric and intestinal conditions and revealed that systems containing higher concentrations of MAA experienced the highest degree of hydrogen bonding complexation in gastric conditions. The presence of NVP in the systems enhanced swelling. Equilibrium swelling studies revealed that the mesh size was sufficiently large to allow drug diffusion across the networks.

Development and characterisation of an agar--polyvinyl alcohol blend hydrogel

Numerous authors have reported on hydrogel technologies providing products suitable for applications in biomedical, personal care as well as in nano-sensor applications. Hydrogels fabricated from single polymers have been extensively investigated. However, in many cases a single polymer alone cannot meet divergent demands in terms of both properties and performance. In this work, hydrogels were prepared by physically blending the natural polymer agar with polyvinyl alcohol in varying ratios to produce a new biosynthetic polymer applicable for a variety of purposes. Hydrogen bonding was observed to take place between the polyvinyl alcohol and the agar molecules in the composite materials leading to changes in the thermal, mechanical and swelling characteristics of the composite hydrogels. The composite hydrogels exhibited a slightly higher melting temperature than pure agar (116.81 degrees C). Irreversible compressive damage was found to occur at lower strain levels during compression testing of the dehydrated samples consisting of higher PVOH concentrations. Rheological analysis of hydrated sample revealed G' values of between 5000 and 10,000 Pa for the composite blends, with gels containing higher PVOH percentages exhibiting poorer mechanical strength.

Synthesis of N-vinylpyrrolidone modified acrylic acid copolymer in supercritical fluids and its application in dental glass-ionomer cements

Compressed fluids such as supercritical CO(2) offer marvellous opportunities for the synthesis of polymers, particularly in applications in medicine and dentistry. It has several advantages in comparison to conventional polymerisation solvents, such as enhanced kinetics and simplified solvent removal process. In this study, poly(acrylic acid-co-itaconic acid-co-N-vinylpyrrolidone) (PAA-IA-NVP), a modified glass-ionomer polymer, was synthesised in supercritical CO(2) (sc-CO(2)) and methanol as a co-solvent. The synthesised polymer was characterized by (1)H-NMR, Raman and FT-IR spectroscopy and viscometry. The molecular weight of the final product was also measured using static light scattering method. The synthesised polymers were subsequently used in several glass ionomer cement formulations (Fuji II commercial GIC) in which mechanical strength (compressive strength (CS), diametral tensile strength (DTS) and biaxial flexural strength (BFS)) and handling properties (working and setting time) of the resulting cements were evaluated. The polymerisation reaction in sc-CO(2)/methanol was significantly faster than the corresponding polymerisation reaction in water and the purification procedures were simpler for the former. Furthermore, glass ionomer cement samples made from the terpolymer prepared in sc-CO(2)/methanol exhibited higher CS and DTS and comparable BFS compared to the same polymer synthesised in water. The working properties of glass ionomer formulations made in sc-CO(2)/methanol were comparable and in selected cases better than the values of those made from polymers synthesised in water.

Multifunctional polyvinylpyrrolidinone-polyacrylic acid copolymer hydrogels for biomedical applications

Copolymers of N-vinylpyrrolidinone and acrylic acid, crosslinked with ethylene glycol dimethacrylate and polyethylene glycol 600 dimethacrylate were prepared by UV-polymerisation. These polymers were analysed for their extractable content by Soxhlet extraction of the samples at 100 degrees C for 72 h. Aspirin and paracetamol were incorporated into the polymer structure at 25 wt.% during the curing process and their presence confirmed by Fourier transform infrared spectroscopy. It was found that the release rate of the drug from the polymer matrix was dependent on intermolecular bonding between the polymer and active agent with aspirin being released slower than paracetamol in all cases. Results showed that paracetamol was completely released after 24h whereas complete release of aspirin took up to 70 h. Finally preliminary in vitro biocompatibility testing was performed for crosslinked polyvinylpyrrolidinone, by determining human hepatoma HepG2 cell viability in the MTT assay and DNA damage in the comet assay following direct contact with various concentrations of polyvinylpyrrolidinone-containing media. Cytotoxicity data suggests a dose-dependent effect for both crosslinkers, with concentrations in the range 0.025-2.5 mg ml(-1) showing a marginal decrease in viability to, at most, 70% that of untreated cells. Again DNA migration in the comet assay following short-term exposure to EGDMA crosslinked hydrogels correlates with MTT data.

Synthesis, Swelling Behavior, and Biocompatibility of Novel Physically Cross-Linked Polyurethane-block-Poly(glycerol methacrylate) Hydrogels

Physically cross-linked novel block copolymer hydrogels with tunable hydrophilic properties for biomedical applications were synthesized by controlled radical polymerization of polyurethane macroiniferter and (2,2-dimethyl-1,3-dioxolane) methyl methacrylate. The block copolymers were converted to hydrogels by the selective hydrolysis of poly[(2,2-dimethyl-1,3-dioxolane) methyl methacrylate] block to poly(glycerol methacrylate). The block copolymerization has been monitored by monomer conversion and molecular weight increase as a function of time. It was observed that the polymerization proceeded with a characteristic "living" behavior where both monomer conversion and molecular weight increased linearly, with increasing reaction time. The resulting hydrogels were investigated for their equilibrium water content (EWC), dynamic water contact angles, swelling kinetics, thermodynamic interaction parameters, plasma protein adsorption, and platelet adhesion. Similar to our previous mechanically responsive hydrogels (Mequanint, K.; Sheardown, H. J. Biomater. Sci. Polym. Ed. 2005, 10, 1303-1318), the present results indicated that block copolymer hydrogels have excellent hydrophilicity and swelling behavior with improved modulus of elasticity. The equilibrium swelling was affected by the hydrolysis time, block length of poly(glycerol methacrylate), temperature, and the presence of soluble salts. Fibrinogen adsorption and platelet adhesion were significantly lower for the hydrogels than for the control polyurethane, whereas albumin adsorption increased for the hydrogels in proportion to the contents of poly(glycerol methacrylate). These hydrogels have potential in a number of biomedical applications such as drug delivery and scaffolds for tissue engineering.

New Aspects of the Formation of Physical Hydrogels of Chitosan in a Hydroalcoholic Medium

New aspects concerning the mechanism of formation of chitosan physical hydrogels without any cross-linking agent were studied. The gelation took place during the evaporation of a hydroalcoholic solution of chitosan. We first demonstrated that it was possible to form a physical hydrogel from a hydrochloride form of chitosan. Chromatographic methods showed that during the gel formation, when the initial concentration is over C, the critical concentration of chain entanglement, the water and acid used for the solubilization of the polymer were both eliminated. This particular situation contributed to decrease the dielectric constant of the medium and the apparent charge density of chitosan chains, thus inducing the formation of a three-dimensional network through hydrophobic interactions and hydrogen bonding. In the gelation process, this step was kinetically determining. The speed of evaporation of water and acid were determined and different initial conditions were compared. Thus, we investigated the influence of: the initial polymer concentration, the nature of the counterion and the alcohol, the temperature and the geometry of the reactor. Our results allowed us to confirm the existence of a second critical initial concentration C, from which the evaporation of water became more difficult. We suggested that C corresponded to a reorganization of the solution involving the presence of gel precursors. Then, a mechanism of formation of physical hydrogels of chitosan in a hydroalcoholic medium could be proposed. For the first time, we demonstrated that it was possible to generate physical hydrogels in the presence of various diols, which size of the carbonated chain appeared as a limiting factor for the gelation process. These physical hydrogels of chitosan are currently used in our laboratory for tissue engineering in the treatment of third degree burns with the possibility to adapt their mechanical properties from the choice of both the acid or the alcohol used.

In vitro characterization of vascular endothelial growth factor and dexamethasone releasing hydrogels for implantable probe coatings

Anti-fouling hydrogel coatings, copolymers of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidinone, and polyethylene glycol, were investigated for the purpose of improving biosensor biocompatibility. These coatings were modified to incorporate poly(lactide-co-glycolide) (PLGA) microspheres in order to release dexamethasone (DX) and/or vascular endothelial growth factor (VEGF). DX and VEGF release kinetics from microspheres, hydrogels, and microspheres embedded in hydrogels were determined in 2-week and 1-month studies. Overall, monolithic, non-degradable hydrogel drug release had an initial burst followed by release at a significantly lower amount. Microsphere drug release kinetics exhibited an initial burst followed by sustained release for 1 month. Embedding microspheres in hydrogels resulted in attenuated drug delivery. VEGF release from embedded microspheres, 1.1+/-0.3 ng, was negligible compared to release from hydrogels, 197+/-33 ng. After the initial burst from DX-loaded hydrogels, DX release from embedded microspheres was similar to that of hydrogels. The total DX release from hydrogels, 155+/-35 microg, was greater than that of embedded microspheres, 60+/-6 microg. From this study, hydrogel sensor coatings should be prepared incorporating VEGF in the hydrogel and DX either in the hydrogel or in DX microspheres embedded in the hydrogel.