Swelling behavior and morphological properties of semi-IPN hydrogels based on ionic and non-ionic components.

Semi-interpenetrating polymer network (IPN) hydrogels with different compositions of poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA) and poly(acrylamide) (PAAm) were synthesized via free radical polymerization using ethylene glycol dimethacrylate (EGDMA) as crosslinker. The variations of swelling percentages (S%) with time, temperature and pH were determined for all hydrogels. Average S% values at pH=7.4 and 37°C were determined to be 1660% for PAA/PVA, the most swollen hydrogel, and 550% for PAAm/PVA, the least swollen IPN-hydrogel. Swelling behaviors based on ionic and non-ionic components were also explained with detailed SEM micrographs of the hydrogels.

Lipase release through semi-interpenetrating polymer network hydrogels based on chitosan, acrylamide, and citraconic acid.

In this study, a series of semi-interpenetrating polymer network (IPN) hydrogels were prepared as a support material for lipase immobilization. Hydrogels were synthesized via free radical polymerization in different compositions of chitosan (Cs), acrylamide (AAm), and citraconic acid (CA). The swelling values of the hydrogels were found to be 240-400%. Depending on the swelling results, Cs-P(AAm-co-CA)-2 hydrogel was chosen for lipase immobilization. Three different types of immobilization technique were carried out. Lipase release behaviors were investigated, and immobilization yields of three immobilization methods were compared, and the maximum immobilization yield value was determined for entrapment method.

Sequential antibiotic and growth factor releasing chitosan-PAAm semi-IPN hydrogel as a novel wound dressing.

The aim of this study is to prepare a novel wound dressing material which provides burst release of an antibiotic in combination with sustained release of growth factor delivery. This might be beneficial for the prevention of infections and to stimulate wound healing. As a wound dressing material, the semi-interpenetrating network (semi-IPN) hydrogel based on polyacrylamide (PAAm) and chitosan (CS) was synthesized via free radical polymerization. Ethylene glycol dimethacrylate was used for cross-linking of PAAm to form semi-IPN hydrogel. The hydrogel shows high water content (∼1800%, in dry basis) and stable swelling characteristics in the pH range of the wound media (∼4.0-7.4). The antibiotic, piperacillin-tazobactam, which belongs to the penicillin group was loaded into the hydrogel. The therapeutic serum dose of piperacillin-tazobactam for topic introduction was reached at 1st hour of the release. Additionally, in order to increase the mitogenic activity of hydrogel, epidermal growth factor (EGF) was embedded into the CS-PAAm in different amounts. Cell culture studies were performed with L929 mouse fibroblasts and the simulated cell growth was investigated by 3-(4,5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide assay. The successful sustained release behavior of CS-PAAm hydrogel for EGF maintained the presence of EGF in the culture up to 5 days and the highest mitochondrial activities were recorded for the 0.4 µg EGF-loaded/mg of hydrogel group. In conclusion, CS-PAAm semi-IPN hydrogel loaded with piperacillin-tazobactam and EGF could be proposed for an effective system in wound-healing management.

Preparation and characterization of gelatin hydrogel support for immobilization of Candida rugosa lipase.

A series of gelatin hydrogels were prepared by crosslinking method using glutaraldehyde (GA). The hydrogels were characterized by gel formation, swelling/degradation tests, and FTIR analysis. The variations of swelling percentages (S%) with time, temperature, and pH were determined. It is found that the increasing amount of GA causes the decreasing in S% values from 366 to 213% and G-1 was found to be the most swollen hydrogel at pH 7.4 and 37 °C. Degradation tests of hydrogel samples were carried out and G-1 hydrogel, which contained the least amount of GA, degraded more rapidly than the others. G-2 hydrogel was chosen for immobilization studies and this procedure was carried out by activation of the hydrogel disc with N-(3-dimethylaminopropyl)-N-ethylcarbodiimid (CDI) coupling agent. The kinetic parameters, K(m) and V(max), were calculated. K(m) values of free and immobilized lipases were found to be 0.290, 0.422 mM while V(max) values were calculated as 0.089, 0.080 mM.min(-1), respectively. For the free and immobilized system, the enzymes retained 32% and 92% of their initial activities, respectively, at the end of 48 days of storage. After using the mentioned immobilized system repeatedly 10 times, it retained 68% of its original activities.

Fluconazole release from hydrogels including acrylamide-acrylic acid-itaconic acid, and their microbiological interactions.

Polyacrylamide (PAAm), polyacrylic acid (PAA), poly(acrylamide-co-itaconic acid) (PAAmIA) and poly(acrylic acid-co-itaconic acid) (PAAIA) hydrogels were prepared via free-radical polymerization using ethylene glycol dimethacrylate (EGDMA) as cross-linker. The variations of swelling percentages with time and pH were determined for these hydrogels at 37 degrees C. PAAmIA was found as the most swollen hydrogel at pH 4.0. SEM micrographs were taken to observe the morphology of the hydrogels. The less swollen hydrogel, PAAIA, displays less porosity relative to PAAmIA hydrogel. Fluconazole was entrapped into PAAmIA and PAAIA hydrogels and the release was investigated in Britton-Robinson buffer solution (BR) at pH 4.0 and 37 degrees C. The kinetic release parameters of the hydrogels, n and k, were calculated and Fickian-type diffusion was established for PAAmIA, which releases Fluconazole faster than PAAIA hydrogel. Therapeutic range was reached in the first hour for both hydrogels. Microbiological interactions of hydrogels were also studied in vitro in vaginal medium. It is found that Fluconazole entrapped in hydrogels inhibited the growth of Candida albicans.

The release of bovine serum albumin from polyurethane based hydrophilic and hydrophobic disks and microbiological interactions.

Polyurethane (PU) based hydrophobic and hydrophilic disks were prepared by graft copolymerization of PU with vinyl monomers, acryl amid (AAm), itaconic acid (IA), acrylic acid (AA) and crotonic acid (CA). Grafting reactions were performed in PU-dioxane solution using benzoyl peroxide as initiator. Air-water and cyclohexan-water contact angle values of the disks (thetaair and thetacy) were measured via "Captive Bubble Method". Surface free energy values of the disks were determined by using thetaair and thetacy via "Two Liquid Method" and those were compared with the swelling percentage values of the disks. The release of Bovine Serum Albumin (BSA) from protein added hydrophilic and hydrophobic PU disks were defined by spectrophotometric measurements at lambda=278 nm in phosphate buffer saline (PBS). BSA releasing is completed around 48 h for all disks. The disks were also characterized by FTIR spectra and SEM micrographs. In vitro attachment of Candida albicans (C. albicans) and Lactobacillus plantarum (L. plantarum) on PU based hydrophilic and hydrophobic disks was studied at 37 degrees C. While C. albicans attached on to all disks, L. plantarum only selectively attached. The attachment percentage values of C. albicans (25%) and L. plantarum (20%) on hydrophobic PU disk were higher than hydrophilic PU disks. The antimicrobial activity of disks was also tested against C. albicans and L. plantarum. IA and AAm grafted PU disks showed inhibitory effect for the both test bacteria.

Adsorption of bovine serum albumin onto surface-modified polyhydroxyethyl methacrylate beads.

The adsorption of bovine serum albumin (BSA) onto poly(2-hydroxyethyl methacrylate) (PHEMA) beads modified by using the pair of hexamethylene diisocyonate-suberic acidbis-N-hydroxy succinimide has been studied as a function of protein concentration and adsorption time. The adsorption studies were carried out in phosphate buffer solution (PBS) at pH = 7.4. The isotherm data have been analysed using the Langmuir model and the adsorption parameters Q0 and b were calculated. It is determined that the adsorbed amount of BSA increases by the increase of the adsorption time and BSA concentration until a certain value. PHEMA beads were characterized by using FTIR spectra and SEM analysis. The adsorption of BSA onto PHEMA beads were clearly observed from SEM micrographs. The swelling tests of the beads were performed at 37 degrees C in PBS.

Microbiological interaction and diffusion properties of hydrophilic and hydrophobic PU membranes.

In this study, the diffusion characteristics of Diclofenac-Na through hydrophobic and hydrophilic polyurethane (PU) based membranes are investigated. Hydrophilic polymers are obtained via graft copolymerization of PU with acrylic acid (AA) and crotonic acid (CA). The membranes are prepared by solvent-casting method and characterized by FTIR spectra and SEM analysis. The diffusion measurements are performed using a diffusion cell during 10 h at 37 degrees C. Permeability coefficients calculated from diffusion experiments are found to be approximately three times higher in hydrophilic membrane than hydrophobic PU membrane. The adherence of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) onto the membranes at 37 degrees C were also investigated. It is determined that the microorganisms didn't adhere onto the membranes compared by control suspension.