Design of sterculia gum based double potential antidiarrheal drug delivery system

In view of the antidiarrheal properties of sterculia gum and ornidazole, an attempt has been made to synthesize novel hydrogels by functionalization of sterculia gum with poly(vinylpyrrolidone) (PVP) for release of the model antidiarrheal drug ornidazole. These hydrogels were characterized with FTIR, SEM, TGA and swelling behavior. Swelling kinetics of the hydrogels and in vitro release dynamics of ornidazole from the drug loaded hydrogels have been studied to determine the mechanism of swelling and drug release from the drug loaded hydrogels. A Fickian diffusion mechanism has been observed for the release of drug from the hydrogels. These hydrogels may have dual actions for the treatment of diarrhea.     

Development of sterculia gum based wound dressings for use in drug delivery

The present study deals with the modification of sterculia gum to develop the novel wounds dressing for the delivery of antimicrobial agent (tetracycline hydrochloride). The sterculia crosslinked PVA (sterculia-cl-PVA) hydrogels were characterized by FTIR and swelling studies. For the evaluation of swelling and drug release mechanism, the swelling kinetics and in vitro release dynamics of model drug from this matrix were studied in solution of different pH and simulated wounds fluid. Per gram of polymer has taken (8.3 ± 0.1) g of simulated wounds fluid and has released (0.820 ± 0.6) mg of drug in the simulated fluid. The value of the ‘n’ (0.84) indicates the non-Fickian diffusion mechanism for the release of drug in simulated fluids.     

Hydrogels for colon‐specific drug delivery: Swelling kinetics and mechanism of degradation in vitro

Hydrogels based on n‐alkyl methacrylate esters (n‐AMA) of various chain lengths, acrylic acid, and acrylamide crosslinked with 4,4′‐di(methacryloylmino)azobenzene were prepared. Swelling kinetics and the mechanism of degradation in vitro of the hydrogels as well as the mutual relations between both were studied by the immersion of slabs in buffered solutions at pH 7.4. The diffusion of water into the slabs was discussed on the stress‐relaxation model of polymer chains. The results obtained agreed well with Schott's second‐order diffusion kinetics. The gels are degradable by anaerobes in the colon. The results obtained showed that the degradation of networks proceeded via a pore mechanism. The factors influencing the swelling and degradation of the gels include the degree of crosslinking, the lengths of the n‐AMA side chains, and the composition. These hydrogels have the potential for colon‐specific drug delivery. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3128–3137, 2001     

The Influence of Preparation Methods on the Swelling and Network Properties of Acrylamide Hydrogels with Crosslinkers

Abstract

Using different types and concentrations of crosslinkers, acrylamide (AAm) hydrogels have been prepared with chemical initiation and gamma irradiation techniques. The effects of the preparation method, crosslinkers type and concentration on swelling behavior of AAm hydrogels were investigated. Swelling was performed in distilled water and followed gravimetrically. Swelling parameters such as equilibrium swelling degree, equilibrium water content (EWC), maximum swelling, initial swelling rate, diffusion exponent and coefficient, and network parameters such as molecular mass between crosslinks, crosslink density, mesh size, and porosity were calculated and evaluated. The range of equilibrium swelling degree of AAm hydrogels was varied from 255% to 1450% depending upon the preparation method, crosslinker type, and crosslinker concentration. The diffusion of water into AAm hydrogels was found to be nonFickian.     

Modification of Dietary Fiber Psyllium with Poly(vinyl pyrrolidone) through Network Formation for Use in Slow Drug Delivery Application

In view of the pharmacological importance of dietary fibre, psyllium, to cure the constipation and diverticulitis, in the present study, an attempt has been made to modify psyllium polysaccharide with PVP to develop the hydrogel meant for slow and controlled drug delivery systems. The polymer was characterized by SEMs, FTIR, XRD, TGA and swelling studies. Swelling of hydrogels and drug (ciprofloxacin) release profile from the drug loaded hydrogels were determined for the evaluation of the swelling/release mechanism. Biomedical properties; biocompatibility and mucoadhesion of the hydrogels, were also studied. Swelling of the hydrogels and release of drugs from drug loaded hydrogels occurred through non-Fickian diffusion mechanism. Here it is pertinent to mention that both psyllium husk polysaccharide and antibiotic drug ciprofloxacin are used for gastrointestinal tract (GIT) problem, especially in case of diverticulitis. Hence, degradation of the polymer matrix and release of drug may exert the synergic effect and the present drug delivery system may act with enhanced potential.     

A pH-Sensitive Hydrogel with Hydrophobic Association for Controlled Release of Poorly Water-Soluble Drugs

A novel pH-sensitive hydrogel has been developed by UV induced radical polymerization of acrylic acid (AA) and amphiphilic macromonomer polyethylene glycol monolaurylether monoacrylate (PEGLA) with crosslinker ethylene glycol dimethacrylate for controlled release of acyclovir, a poor water-soluble model drug. The swelling behavior was investigated in the buffer of different pH at I = 0.1 M, as well as in the ethanol/water mixture. The hydrophobic association formed by the hydrocarbon chains in PEGLA was found to dominate the swelling properties of the hydrogels with subordinate pH sensitivity due to the ionization of the AA segments. Therefore, the drug loading of acyclovir has been improved and the release rate of acyclovir was slowed down with increasing the PEGLA content in the hydrogels. By fitting the release data with Weibull equation, the acyclovir release kinetics was changed from the Fickian diffusion to an anomalous diffusion when the PEGLA content in the hydrogels was beyond 20 mol%.     

Superabsorbent Hydrogels Based to Polyacrylamide/Cashew Tree Gum for the Controlled Release of Water and Plant Nutrients

Agricultural production is influenced by the water content in the soil and availability of fertilizers. Thus, superabsorbent hydrogels, based on polyacrylamide, natural cashew tree gum (CG) and potassium hydrogen phosphate (PHP), as fertilizer and water releaser were developed. The structure, morphology, thermal stability and chemical composition of samples of polyacrylamide and cashew tree gum hydrogels with the presence of fertilizer (HCGP) and without fertilizer (HCG) were investigated, using X-ray diffractometry (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA/DTG) and Energy Dispersive Spectroscopy (EDS). Swelling/reswelling tests, textural analysis, effect of pH, release of nutrients and kinetics were determined; the ecotoxicity of the hydrogels was investigated by the Artemia salina test. The results showed that PHP incorporation in the hydrogel favored the crosslinking of chains. This increased the thermal stability in HCGP but decreased the hardness and adhesion properties. The HCGP demonstrated good swelling capacity (~15,000 times) and an excellent potential for reuse after fifty-five consecutive cycles. The swelling was favored in an alkaline pH due to the ionization of hydrophilic groups. The sustained release of phosphorus in HCGP was described by the Korsmeyer–Peppas model, and Fickian diffusion is the main fertilizer release mechanism. Finally, the hydrogels do not demonstrate toxicity, and HCGP has potential for application in agriculture.     

Development,characterization, swelling,and network parameters of amino acid grafted guar gum based pH responsive polymeric hydrogels

This study includes the synthesis of graft copolymer (GG-g-PAPA) from N-Acryloyl-L-phenylalanine (APA) and guar gum through free radical polymerization. Then, the novel pH sensitive GG-g-PAPA-cl-(PHEA-co-PAMPS) [GGAH] polymeric hydrogels were synthesized by employing free radical cross-linking polymerization using graft copolymer, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), and 2-hydroxy ethyl acrylate (HEA). The GGAH hydrogels were characterized using FTIR and SEM. Swelling studies of GGAH hydrogels were performed in distilled water, pH 1.2, and pH 7.4 solutions. The network and swelling kinetic parameters of GGAH hydrogels are also calculated.     

Konjac glucomannan‐graft‐acrylic acid hydrogels containing azo crosslinker for colon‐specific delivery

In this article, the synthesis and characterization of novel hydrogel systems designed for colon‐targeting drug delivery are reported. The gels were composed of konjac glucomannan, copolymerized with acrylic acid, and crosslinked by the aromatic azo agent bis(methacryloylamino)‐azobenzene. The influence of various parameters on the dynamic and equilibrium swelling ratios (SRs) of the hydrogels was investigated. It is shown that the SR was inversely proportional to the grafting degree of acrylic acid and the content of bis(methacryloylamino)‐azobenzene. The dependence of SR on the pH indicates that obtained hydrogels are potential for drug delivery to colon. It was possible to modulate the degree of swelling and the pH sensitivity of the gels by changing crosslinking density of the polymer. The main chain of hydrogels can be degraded by β‐glycosidase which is abundant in colon. They can be in vitro degraded for 73% in a month by Cereflo® and 86% in 20 days by Mannaway25L. We have also prepared the hydrogels that loaded with bovine serum albumin about 1.5%, 3%, 9%, and 20% by weight. In vitro release of model drug bovine serum albumin was studied in the presence of Mannaway25L or Fungamyl®800L in pH 7.4 phosphate buffer at 37 °C. The drug release can be controlled by the biodegradation of the hydrogels. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4370–4378, 2004     

Synthesis of Carboxymethyl Cellulose Based Drug Carrier Hydrogel Using Ionizing Radiation for Possible Use as Site Specific Delivery System

A unique natural polymer based colon specific drug carrier was prepared from carboxymethyl cellulose (CMC) and acrylic acid (AAc) in aqueous solution employing γ‐radiation induced copolymerization and crosslinking. The effect of preparation conditions such as the natural polymer content and irradiation dose on gelation process was investigated. The swelling behavior of the prepared hydrogels was characterized by investigating the time and pH dependent swelling of the (CMC/AAc) hydrogels of different CMC content. The effects of the hydrogel composition and pH of the swelling medium on the swelling indices were estimated. The results show that the increment in the CMC content in the feed solution enhances the gelation process. The results also show the dependence of the swelling indices on both hydrogel composition and pH value of the swelling medium. To evaluate the ability of the prepared hydrogel to be used as a colon‐specific drug carrier, the release profile of theophylline was studied as a function of time at pH 1 and pH 7.     

Crosslinked Networks Based on Polysaccharides and Collagen for Pilocarpine Sustained Release

The paper presents the experimental studies regarding synthesis and characterization of hydrogels based on gellan (Gel)/chitosan (CS) and collagen (Col), obtained by crosslinking with glutaraldehyde (GLA). The influence of the polysaccharide content and GLA ratio on the final composition and swelling characteristics was evaluated. Hydrogels swelling analysis, in distilled water and phosphate buffer (PBS, pH 7.2) has shown higher swelling degrees at increased concentration of polysaccharide into hydrogels. In vitro release of pilocarpine has demonstrated the possibility to use gellan-collagen and chitosan-collagen hydrogels as ophthalmic drug delivery matrix.     

Development of Antibacterial,Degradable and pH-Responsive Chitosan/Guar Gum/Polyvinyl Alcohol Blended Hydrogels for Wound Dressing

The present research is based on the fabrication preparation of CS/PVA/GG blended hydrogel with nontoxic tetra orthosilicate (TEOS) for sustained paracetamol release. Different TEOS percentages were used because of their nontoxic behavior to study newly designed hydrogels’ crosslinking and physicochemical properties. These hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and wetting to determine the functional, surface morphology, hydrophilic, or hydrophobic properties. The swelling analysis in different media, degradation in PBS, and drug release kinetics were conducted to observe their response against corresponding media. The FTIR analysis confirmed the components added and crosslinking between them, and surface morphology confirmed different surface and wetting behavior due to different crosslinking. In various solvents, including water, buffer, and electrolyte solutions, the swelling behaviour of hydrogel was investigated and observed that TEOS amount caused less hydrogel swelling. In acidic pH, hydrogels swell the most, while they swell the least at pH 7 or higher. These hydrogels are pH-sensitive and appropriate for controlled drug release. These hydrogels demonstrated that, as the ionic concentration was increased, swelling decreased due to decreased osmotic pressure in various electrolyte solutions. The antimicrobial analysis revealed that these hydrogels are highly antibacterial against Gram-positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Pseudomonas aeruginosa and Escherichia coli) bacterial strains. The drug release mechanism was 98% in phosphate buffer saline (PBS) media at pH 7.4 in 140 min. To analyze drug release behaviour, the drug release kinetics was assessed against different mathematical models (such as zero and first order, Higuchi, Baker–Lonsdale, Hixson, and Peppas). It was found that hydrogel (CPG2) follows the Peppas model with the highest value of regression (R² = 0.98509). Hence, from the results, these hydrogels could be a potential biomaterial for wound dressing in biomedical applications.     

干燥方式对含直链淀粉半互穿网络水凝胶溶胀和降解的影响

以4,4′-二甲基丙烯酰胺基偶氮苯(BMAAB)为交联剂,制备了丙烯酸-丙烯酰胺-甲基丙烯酸酯共聚物和直链淀粉半互穿网络水凝胶.以冷冻干燥和空气干燥两种方式,研究了干凝胶在pH2.2和pH7.4时的溶胀和降解性能.结果表明采用两种干燥方式的凝胶在不同pH的介质中都遵循二级溶胀动力学.凝胶内部水的扩散均为非Fickian机理,即扩散和链松弛协同作用的机理.但经历冷冻干燥的凝胶其扩散机制占优势.在pH=7.4的介质中,冷冻干燥凝胶的平衡溶胀比(SR)显著增大,而在pH=2.2时则无明显变化.扫描电镜(SEM)和降解实验发现,在结肠内容物的作用下,冷冻干燥凝胶在5天内降解率可达35.3%,而空气干燥凝胶的降解率为28.1%,表明冷冻干燥的方式可在一定程度上促进凝胶在结肠环境下的降解.     

Investigation of drug release from thermo‐ and pH‐sensitive poly(N‐isopropylacrylamide/itaconic acid) copolymeric hydrogels

N‐Isopropylacrylamide/itaconic acid copolymeric hydrogels were prepared by irradiation of the ternary mixtures of N‐isopropylacrylamide/itaconic acid/water by γ‐rays at ambient temperature. The dependence of swelling properties and phase transitions on the comonomer concentration and temperature were investigated. The hydrogels showed both temperature and pH responses. The effect of comonomer concentration on the uptake and release behavior of the hydrogels was studied. Methylene blue (MB) was used as a model drug for the investigation of drug uptake and release behavior of the hydrogels. The release studies showed that the basic parameters affecting the drug release behavior of the hydrogels were pH and temperature of the solution. Copyright © 2004 John Wiley & Sons, Ltd.     

Formulation and Evaluation of Self‐Regulated Insulin Delivery System Based on poly(HEMA‐co‐DMAEMA) Hydrogels

In the present work a self‐regulated insulin delivery system based on the hydrogel poly(2‐hydroxyethyl methacrylate‐co‐N,N‐dimethylaminoethyl methacrylate) with entrapped glucose oxidase, catalase and insulin was developed and evaluated both by in vitro and in vivo studies. The hydrogels were characterized by FTIR, DSC, SEM and elemental analysis. The swelling studies were carried out in different pH and glucose solutions. The mesh size of the hydrogels and diffusion coefficient of water and insulin in different glucose solution was calculated. The effect of the crosslinking agent (ethylene glycol dimethacrylate) concentration (0–2% w/w) on swelling and insulin release was studied. The equilibrium swelling and insulin release was found to depend on the external glucose concentration and dimethylaminoethyl methacrylate content of the hydrogels. The in vivo studies indicated that the entrapped insulin was stable and was effective in reducing the blood glucose of streptozotocin induced diabetic rats. The histopathological studies revealed that there was no fibrous tissue encapsulation after 56 days of implantation.     

Physicochemical characterization and drug release properties of PDMAEMA/OSA Semi‐IPN hydrogels with microporous structure

A new poly(2‐(dimethylamino) ethyl methacrylate)/oxidized sodium alginate (PDMAEMA) semi‐interpenetrating network (Semi‐IPN) hydrogel with microporous structure was prepared by using PDMAEMA microgels as an additive during the polymerization/crosslinking process. The interior morphology characterized by scanning electron microscopy showed the Semi‐IPN hydrogels have different pore sizes by changing the amount of microgels. The hydrogels were also characterized by using Fourier transform infrared and DSC. The swelling behaviors of hydrogels indicated that the hydrogels have excellent pH and temperature sensitivity. Bovine serum albumin was entrapped in the hydrogels and the in vitro drug release profiles were established in different buffer solutions at various temperatures. The release behaviors of the model drug were dependent on the pore size of the hydrogels and environmental temperature/pH, which suggested that these materials have potential application as intelligent drug carriers. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis,characterization, and evaluation of enzymatically degradable poly(N‐isopropylacrylamide‐co‐acrylic acid) hydrogels for colon‐specific drug delivery

The enzymatically degradable poly(N‐isopropylacrylamide‐co‐acrylic acid) hydrogels were prepared using 4,4^′‐bis(methacryloylamino)azobenzene (BMAAB) as the crosslinker. It was found that the incorporated N‐isopropylacrylamide (NIPAAm) monomer did not change the enzymatic degradation of hydrogel, but remarkably enhanced the loading of protein drug. The hydrogels exhibited a phase transition temperature between 4°C (refrigerator temperature) and 37°C (human body temperature). Bovine serum albumin (BSA) as a model drug was loaded into the hydrogels by soaking the gels in a pH 7.4 buffer solution at 4°C, where the hydrogel was in a swollen status. The high swelling of hydrogels at 4°C enhanced the loading of BSA (loading capability, ca. 144.5 mg BSA/g gel). The drug was released gradually in the pH 7.4 buffer solution at 37°C, where the hydrogel was in a shrunken state. In contrast, the enzymatic degradation of hydrogels resulted in complete release of BSA in pH 7.4 buffer solution containing the cecal suspension at 37°C (cumulative release: ca. 100 mg BSA/g gel after 4 days). Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,characterization and evaluation of semi‐IPN hydrogels consisted of poly(methacrylic acid) and guar gum for colon‐specific drug delivery

The semi‐IPN hydrogels consisting of poly(methacrylic acid) and guar gum (GG) are prepared at room temperature using water as solvent. 5‐aminosalicylic acid (5‐ASA) is entrapped in the hydrogel in the synthesis of hydrogel and all entrapment efficiencies are found above 85%. The hydrogel shows excellent pH‐sensitivity. It exhibited minimum swelling in an acidic pH medium through the formation of a complex hydrogen‐bonded structure and maximal swelling due to the electrostatic repulsion due to the ionization of the carboxylic groups in pH 7.4 medium. The degradation in vitro shows that the degree of degradation (R%) depended on the concentration of cross‐linking agent and content of GG. The hydrogel shows a minimum release of 5‐ASA due to the complex hydrogen bonded structure of the hydrogels in the medium of pH 2.2. The enzymatic degradation of hydrogels by cecal bacteria can accelerate the release of 5‐ASA entrapped in the hydrogel in pH 7.4 medium. Copyright © 2007 John Wiley & Sons, Ltd.     

A novel pH‐ and thermo‐sensitive PVP/CMC semi‐IPN hydrogel: Swelling,phase behavior,and drug release study

Poly(N‐vinyl‐pyrrolidone) (PVP) hydrogel has been considered as a very interesting and promising thermosensitive material. The most vital shortcoming of PVP hydrogel as thermosensitive material is that it does not exhibit thermosensitivity under usual conditions. In this work, semi‐interpenetrating polymer network (semi‐IPN) hydrogels based on PVP and carboxymethylcellulose (CMC) were prepared. The volume phase transition temperature (VPTT) of the hydrogels was determined by swelling behavior and differential scanning calorimetry (DSC). The results showed that the VPTT was significantly dependent on CMC content and the pH of the swelling medium. The amount of CMC in the semi‐IPN hydrogels was 0.050, 0.075, and 0.100 g, the VPTT in buffer solution of pH 1.2 was 29.9 °C, 27.5 °C and 24.5 °C, respectively. In addition, the VPTT occurred in buffer solution of pH 1.2, but did not appear in alkaline medium. Bovine serum albumin (BSA) as a model drug was loaded and the in vitro release studies were carried out in different buffer solutions and at different temperatures. The results of this study suggest that PVP/CMC semi‐IPN hydrogels could serve as potential candidates for protein drug delivery in the intestine. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1749–1756, 2010     

Surface modification by deposition of IPA plasma and gellan gum/chitosan hybrid hydrogel onto thermoplastic polyurethane for controlled release of N‐acetylcysteine

A thin film system composed of gellan gum and chitosan was fabricated through a combination of polyelectrolyte blend and hybrid hydrogel gelation for controlled release of drug. In this study, precursor isopropyl alcohol (IPA) was used to plasma deposit on the surface of thermoplastic polyurethane (TPU) to form a hydrophilic film. The features of the thin film were evaluated using water contact angle (WCA) measurement, scanning electron microscopy (SEM), Fourier transform infra‐red (FTIR), UV/Vis spectroscopy, and studies of controlled release of drugs. The hybrid hydrogel, pH‐sensitive, was tested at pH values of 1.2 and 7.4 of buffer solution and at a temperature of 37°C to observe its swelling ratio and drug delivery properties with N‐acetylcysteine as a drug material for controlled release. Furthermore, at pH 7.4, the hybrid hydrogel has an outstanding release ratio of up to about 90% absorption amounts of N‐acetylcysteine after 8 hr. The mechanism of drug release from thin film devices (n = 0.684) is anomalous (non‐Fickian) transport, the value of n lies between 0.43 and 0.85.