Preparation of pH‐sensitive poly(vinyl alcohol‐g‐methacrylic acid) and poly(vinyl alcohol‐g‐acrylic acid) hydrogels by gamma ray irradiation and their insulin release behavior

A series of pH‐responsive hydrogels were studied as potential drug carriers for the protection of insulin from the acidic environment of the stomach before releasing in the small intestine. Hydrogels based on poly(vinyl alcohol) networks grafted with acrylic acid or methacrylic acid were prepared by a two‐step process. Poly(vinyl alcohol) hydrogels were prepared by gamma ray irradiation (50 kGy) and then followed by grafting either acrylic acid or methacrylic acid onto these poly(vinyl alcohol) hydrogels with subsequent irradiation (5–20 kGy). These graft hydrogels showed pH‐sensitive swelling behavior and were used as carriers for the controlled release of insulin. The in vitro release of insulin was observed for the insulin‐loaded hydrogels in a simulated intestinal fluid (pH 6.8) but not in a simulated gastric fluid (pH 1.2). The release behavior of insulin in vivo in a rat model confirmed the effectiveness of the oral delivery of insulin to control the level of glucose. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 636–643, 2004     

Grafting of acrylic acid onto flax fibers using Mn(IV)‐citric acid redox system

When the flax fibers (machine tow) were treated with KMnO₄ solution, MnO₂ was deposited over‐all the fiber surface. The amount of MnO₂ deposited relied on the KMnO₄ concentration. Subjecting the flax‐containing MnO₂ to a solution consisting of monomer (acrylic acid, AA) and citric acid, CA (or any acid used in this work) resulted in formation of poly(AA)‐flax graft copolymer. Dependence of the polymer criteria, namely, the total percentage conversion (%TC) and the carboxyl content of the grafted flax fibers on various grafting parameters, viz., concentrations of the redox pair as well as AA, material‐to‐liquor ratio (M/R), duration and temperature of polymerization, kind of the acid and kind of the flax fibers pretreatment was studied systematically. The results indicated that the polymerizability of AA molecules, expressed as %TC (i.e., counting both grafting and homopolymerization) and thence the carboxyl content (i.e., evaluating the extent of AA grafting along the flax backbone) was optimized with the following conditions: [AA], 100% (based on weight of flax fibers, owf); [CA], 0.4 meq/1 g flax; [MnO₂], 0.4 meq/1 g flax; polymerization temperature, 40°C; polymerization time, 30 min; and the M/R, 1 : 50. A tentative mechanism for grafting of flax fibers with AA using MnO₂‐acid redox system was elucidated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3028–3036, 2006     

Hollow poly(N‐isopropylacrylamide)‐co‐poly(acrylic acid) microgels with high loading capacity for drugs

A convenient approach has been developed for the preparation of microsize hydrogels composed of crosslinked poly(acrylic acid) (PAA) and poly(N‐isopropylacrylamide) (PNIPAm). First, semi‐interpenetration polymer networks of hydropropylcellulose (HPC) and PNIPAm‐co‐PAA copolymer are formed through the copolymerization and crosslinking of monomer acrylic acid and N‐isopropylacrylamide in HPC aqueous solution. After the selective removal of HPC from networks due to ionization of PAA units and disruption of hydrogen bonding with increasing pH, PNIPAm‐co‐PAA microgels are obtained, whose volume is confirmed to be responsive to both temperature and pH. Doxorubicin hydrochloride (Dox) can be encapsulated in PNIPAm‐co‐PAA microgels with high drug loading driven by the electrostatic interaction, and a sustained‐release characteristic of Dox from the microgels is observed under physiological pH value and temperature. In vitro cell experiments, the drug‐loaded microgels can be taken up by LoVo cells and release their payload in cell cytoplasm without loss of drug efficacy. This indicates that PNIPAm‐co‐PAA microgels might be a potential drug delivery carriers especially for water‐soluble or polypeptide drugs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Antibacterial functionalization of cotton fabrics by electric‐beam irradiation

An N‐halamine precursor monomer, 2,2,6,6‐tetramethylpiperidinyl acrylate (TMPA), was synthesized and successfully grafted onto cotton fibers via an impregnation process (IP) and electron‐beam irradiation (EB). The grafted cotton fibers could provide antibacterial efficacy after chlorination through a dilute sodium hypochlorite solution. The antibacterial efficacy was challenged against Staphylococcus aureus and Escherichia coli. The cotton fibers grafted with TMPA and acrylic acid by EB inactivated all of the bacteria within 30 min of contact, whereas the samples grafted with TMPA via an IP could not completely kill the bacteria with 60 min. The breaking strength and UVA light stability also improved significantly. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42023.     

Isothermal kinetics of (E)‐4‐(4‐metoxyphenyl)‐4‐oxo‐2‐butenoic acid release from a poly(acrylic acid‐co‐methacrylic acid) hydrogel

A kinetic study of the release of the drug (E)‐4‐(4‐metoxyphenyl)‐4‐oxo‐2‐butenoic acid (MEPBA) from a poly(acrylic acid‐co‐methacrylic acid) (PAA‐co‐MA) hydrogel was performed. The isothermal kinetic curves of MEPBA release from the PAA‐co‐MA hydrogel in bidistilled water at different temperatures ranging from 20 to 40°C were determined. The reaction rate constants of the investigated process were determined with the initial rate, the saturation rate, and Peppas's semiempirical equation. Also, a model‐fitting method for the determination of the kinetics model of drug release was applied. The influence of α at the values of the kinetic parameters and the presence of a compensation effect was established. A procedure for the determination of the distribution function of the activation energies was developed. This procedure was based on the experimentally determined relationship between the activation energy and α. The mechanism of active compound release is discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Functionalized bacterial cellulose nanowhiskers as long‐lasting drug nanocarrier for antibiotics and anticancer drugs

A nano drug carrier based on sustainable and biocompatible nanocellulose was developed for use in prolonged drug releases. The grafting of β‐cyclodextrin (βCD) on bacterial cellulose nanowhiskers (BCNC) using citric acid (CA) as a green linker was performed. This led to the formation of functionalized BCNC‐grafted‐βCD (BCNC‐g‐βCD). Broad‐spectrum antibiotic Ciprofloxacin (CIP) and anticancer drugs Doxorubicin (DOX) and Paclitaxel (PTX) were used as model drugs. These model drugs were conjugated to BCNC‐g‐βCD to form the drug‐nanocarrier systems (BCNC‐g‐βCD‐drug). The change in the nanowhiskers’ surface chemistry, morphology, and crystallinity was characterized by FTIR, solid‐state ¹³C NMR, scanning electron microscopy (SEM), atomic force microscopy (AFM), and x‐ray diffraction (XRD). The functionalized nanowhiskers showed a significant increase in the drug payloads, which ranged from 495 ±4–810 ±7 μg/mg, along with a radical improvement in the drug release profiles. For all of the developed drug‐conjugated nanocarriers, the initial burst releases were reduced effectively. The observed drug releases showed a sustained and controlled manner, with cumulative releases of 75–90 % over 5–5.5 days. Nevertheless, an improved drug release performance was observed in the acidic pH of 6.4 that mimicked extracellular tumor cells. In vitro drug release data were fitted zero‐order kinetic model with drug release constants (K₀) of 0.68, 0.74, and 0.79 μg drug/h (at pH 6.4 and 37 °C) for BCNC‐g‐βCD‐CIP, BCNC‐g‐βCD‐DOX, and BCNC‐g‐βCD‐PTX nanosystems, respectively. The observed higher payloads along with the slow releases of drugs from the developed nanocarrier suggests its promising potential for reducing the frequent daily dosing and minimizing systemic toxicity of loaded drugs.     

Drug delivery system based on poly(ether‐block‐amide) and acrylic acid for controlled release of vancomycin

Poly(ether‐block‐amide) (PEBA) films were grafted with acrylic acid (AAc) by gamma radiation, using the oxidative pre‐irradiation technique. The effect of dose, monomer concentration, temperature, and reaction time on the graft percentage of AAc onto PEBA was studied. The modified material PEBA‐g‐AAc was characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscopy, and water contact angle. It was found that PEBA films did not suffer degradation at low doses (<30 kGy) during the grafting process. Additionally, PEBA‐g‐AAc was proved as drug delivery system using vancomycin as drug model. The PEBA‐g‐AAc with 39 and 98% of AAc loaded 63 and 98 mg g^?1, respectively. The release profiles showed a sustained delivery by 48 h with a partial retention of drug, which depends of grafting percentage. The microbiological tests showed that PEBA‐g‐AAc was able to inhibit the growing of Staphylococcus aureus in three consecutive challenges. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45745.     

Biodegradable amphiphiles of grafted poly(lactide) onto 2‐hydroxyethyl methacrylate‐co‐N‐vinylpyrrolidone copolymers as drug carriers

This article describes the synthesis and characterization of 2‐hydroxylethyl methacrylate‐co‐N‐vinylpyrrolidone copolymers, (HEMA‐co‐NVP), via free radical polymerization followed by grafting of poly(lactide) onto (HEMA‐co‐NVP) copolymers, via ring opening polymerization using tin octoate as a catalyst. The copolymers and the grafted copolymers (i.e., amphiphiles) were subjected to sustained release studies using salicylic acid, as a model drug. Characterization of the formed copolymers was performed using ¹H‐NMR, ¹³C‐NMR, FTIR, TGA, DSC, and SEM techniques. Derivative of TGA thermogram was used to determine %hydrophilicity and %hydrophobicity in the grafted and ungrafted copolymers. The SEM morphology revealed porous layers with crispy structure that were most likely due to the presence of poly(lactide) chains. At lower content of poly(lactide) moiety, grafted copolymers showed non‐Fickian diffusion release rate, whereas Fickian diffusion release rate at higher content of poly(lactide) was observed. The increase of poly(lactide) content (i.e., larger %hydrophobicity) in the copolymer increased the drug‐sustainability, due to the consistent but porous amphiphilic degradable structures that allow controllable release of drug in time interval. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chemometric study of graft copolymerization of guar‐g‐(acrylamide‐co‐diallyl dimethylammonium chloride)

Chemometrics was employed to study the effect of various reaction conditions on the graft copolymerization of acrylamide (AM) and diallyl dimethylammonium chloride (DADMAC) onto guar gum using the cerous sulfate and potassium persulfate complex initiation system. A two level full factorial design was used to study the effect of reaction parameters on percentage grafting (%G) and monomer conversion (%MC). Synthesized polymers were characterized using Fourier transform infrared spectroscopy (FTIR), ¹H‐NMR (nuclear magnetic resonance spectroscopy), and ¹³C‐NMR and also were analyzed for differences in intrinsic viscosity and charge incurred with changing reaction conditions. The concentration of AM was observed to have the greater effect on %grafting. Interaction effects between the reaction temperature and concentration of AM were also found to be important. Under the reaction condition studied, the highest grafting (%G) was obtained for polymer 1 (0.7M AM concentration, 60°C reaction temperature, and 1M acid concentration). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dynamic release of gentamicin sulfate (GS) from alginate dialdehyde (AD)-crosslinked casein (CAS) films for antimicrobial applications

In the present work, antibiotic drug gentamicin sulfate (GS) has been loaded into alginate dialdehyde-crosslinked casein (CAS) films for wound dressing applications. The films have been characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy. The dynamic release of model drug GS has been investigated in the physiological fluid at 37 °C. The drug release data has been interpreted in the terms of various kinetic models such as Power function model, first order model and Schott model. The release data was found to be well fitted by Schott model. The various diffusion coefficients are also evaluated. The adsorption of model therapeutic protein BSA on the film has been investigated. The maximum adsorption is found to be 5.7 mg/cm².The films were tested for their antibacterial and anti-fungal action. Finally, the in vivo wound healing study was carried out on Albino wistar rats.     

Pectin grafted poly(N‐vinylpyrrolidone): Optimization and in vitro controllable theophylline drug release

The present article describes preparation, optimization, and characterization of pectin grafted polyvinylpyrrolidone hydrogels followed by controllable theophylline drug release. The gels were prepared in the presence of N,N′–methylenebisacrylamide (MBAA) crosslinker and ceric ammonium nitrate (CAN) initiator under N₂ atmosphere. Optimum conditions, in terms of percent of grafting (%G), were determined as follows: Pectin = 1.0 g, [NVP] = 2.81 mM, [MBAA] = 0.65 mM, [CAN] = 0.073 mM, polymerization temperature = 30°C and time = 4.0 hrs. Hydrogels were characterized by FTIR, TGA, DSC, XRD, and SEM. In vitro controllable release of theophylline model drug was studied using different N‐vinylpyrrolidone monomer to MBAA crosslinker ratio (i.e., [NVP]/[MBAA] ratios) and different polymerization temperatures at two pH values, namely 5.5 and 7.4. The optimum conditions for colon‐targeted vehicles that could provide the least theophylline release at pH 5.5, and the most theophylline release at pH 7.4, were as follows: [NVP]/[MBAA] = 4.33, polymerization temperature = 10°C and %G = 62.2. Such promising hydrogel characteristics may play the key role in many future drug release implementations. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Chemically induced graft copolymerization of vinyl monomers onto cotton fibers

We investigated the chemically induced graft copolymerizations of acrylic acid (AA), acrylamide, crotonic acid, and itaconic acid (IA) onto cotton fibers. Benzoyl peroxide was used as an initiator. The effects of grafting temperature, grafting time, and monomer and initiator concentrations on the grafting yields were studied, and optimum grafting conditions were determined for the sample material. The maximum grafting yield value obtained was 23.8% for AA. Swelling tests, Fourier transform infrared spectroscopy, and scanning electron microscopy analyses of grafted and ungrafted fibers were also performed to characterize fiber properties. IA‐grafted fibers were measured as the most swollen fibers, with a swelling value of 510%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2343–2347, 2006     

The enhanced dyeability of aromatic polysulfonamide fibers using γ‐ray irradiation‐induced graft polymerization

Aromatic polysulfonamide fibers (PSA) are impossible to be dyed with conventional dyeing techniques because of their extremely high glass transition temperature (Tg 280～380 °C). To make the PSA fibers dyeable without a carrier under normal pressure, PSA fibers were grafted using γ‐ray irradiation with acrylic acid (AA) as a monomer. In addition to the dyeability, changes in other inherent performance characteristics of PSA fibers after irradiation grafting were evaluated, such as the mechanical behavior, thermal stability, hygroscopicity, and flame retardancy. Meanwhile, the effect of irradiation grafting on the performance of PSA fibers was revealed using structure information in different length scales. The results showed the AA‐grafting copolymerization occurred not only on the surface of PSA fibers, but also in the amorphous region within the fibers. The polyacrylic acid grafted chains could act as an internal plasticizer, enlarging the free volume of fibers, which make the PSA fibers dyeable with a cationic dye and disperse dye. The color fastness of the dyed PSA fibers was strongly reliant on the dye category. The irradiation‐grafting treatment has little adverse effect on the inherent performance of PSA fibers such as mechanical properties, thermal stability and flame retardancy within a proper grafting yield. POLYM. ENG. SCI., 59:592–601, 2019. © 2018 Society of Plastics Engineers     

Poly(Caprolactone)‐Poly(N‐Isopropyl Acrylamide)‐Fe3O4 Magnetic Nanofibrous Structure with Stimuli Responsive Drug Release

Poly(caprolactone; PCL)—poly(N‐isopropylacrylamie; PNIPAAm)—Fe₃O₄ fiber, that can be magnetically actuated, is reported. Here, a structure is engineered that can be utilized as a smart carrier for the release of chemotherapeutic drug via magneto‐thermal activation, with the aid of magnetic nanoparticles (MNPs). The magnetic measurement of the fibers revealed saturation magnetization values within the range of 1.2–2.2 emu g^?1. The magnetic PCL‐PNIPAAm‐Fe₃O₄ scaffold shows a specific loss power value of 4.19 W g^?1 at 20 wt% MNPs. A temperature increase of 40 °C led to a 600% swelling after only 3 h. Doxorubicin (DOX) as a model drug, demonstrates a controllable drug release profile. 39% ± 0.92 of the total drug loaded is released after 96 h at 37 °C, while 25% drug release in 3 h at 40 °C is detected. Cytotoxicity results show no significant difference in cell attachment efficiency between the MNP‐loaded fibers and control while the DOX‐loaded fibers effectively inhibited cell proliferation at 24 h matching the drug release profile. The noncytotoxic effect, coupled with the magneto‐thermal property and controlled drug release, renders excellent potential for these fibers to be used as a smart drug‐release agent for localized cancer therapy.     

Grafting of methyl methacrylate (MMA) onto Antheraea assama silk fiber

Graft copolymerization of methyl methacrylate (MMA) onto nonmulberry silk fiber Antheraea assama was investigated in aqueous medium using the KMnO₄–oxalic acid redox system. Grafting (%) was determined as a function of the reaction time, temperature, and monomer and initiator concentrations. The rate of grafting increased progressively with increase of the reaction time up to 4 h and then decreased. The extent of grafting was maximum at 55°C. The extent was also dependent upon monomer and initiator concentrations up to 75.5 × 10^?2 and 6 × 10^?3 M, respectively. The grafted products were evaluated by infrared spectroscopy and their thermal decompositions were studied by TG and DTG techniques in static air at 20°C min^?1 and 30°C min^?1 in the range 30–800°C. The kinetic parameters for ungrafted and grafted fibers were evaluated using the Coats and Redfern method. The grafted products were found to be thermally more stable than were those of the ungrafted fibers. The surface characteristics of the ungrafted and grafted fibers were evaluated by scanning electron microscopy. The water‐retention values (WRVs) of the grafted fibers were in decreasing order with increase in the grafting (%). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2633–2641, 2001     

DNA adsorption on poly(N,N‐dimethylacrylamide)‐grafted chitosan hydrogels

In this study, poly(N,N‐dimethylacrylamide) grafted chitosan (PDMAAm‐g‐CT) hydrogels were prepared for deoxyribonucleic acid (DNA) adsorption. Instead of directly grafting the N,N‐dimethylacrylamide (DMAAm) monomer onto the chitosan (CT) chains, poly(N,N‐dimethylacrylamide) with carboxylic acid end group (PDMAAm‐COOH) was firstly synthesized by free‐radical polymerization using mercaptoacetic acid (MAAc) as the chain‐transfer agent and then grafted onto the CT having amino groups. The synthesis of PDMAAm‐COOH and its grafting onto the CT chains were confirmed by attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy. From gel permeation chromatography measurements, the number‐average molecular weight (M _n) and polydispersity index of PDMAAm‐COOH were found as 2400 g/mol and 2.3, respectively. The PDMAAm‐g‐CT hydrogels were utilized as the adsorbents in DNA adsorption experiments conducted at +4°C in a trisEDTA solution of pH 7.4. The hydrogels produced with higher PDMAAm‐COOH content exhibited higher DNA adsorption capacity. The DNA adsorption capacity up to 4620 μg DNA/g dry gel could be achieved with the PDMAAm‐g‐CT hydrogels prepared in 80.0 wt % PDMAAm‐COOH feed concentration. This value is approximately seven times higher than that of CT alone. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Grafting of acrylic monomers onto cotton fabric using an activated cellulose thiocarbonate–azobisisobutyronitrile redox system

The feasibility of a cellulose thiocarbonate–azobisisobutyronitrile (AIBN) initiation system to induce graft copolymerization of methyl methacrylate (MMA) and other acrylic monomers onto cotton fabric was investigated. Other acrylic monomers were acrylic acid, acrylonitrile, and methyl acrylate. The initiation system under investigation was highly activated in the presence of a metal‐ion reductant or a metal‐ion oxidant in the polymerization medium. A number of variables in the grafting reaction were studied, including AIBN concentration, pH of the polymerization medium, nature of substrate, monomer concentration, duration and temperature of polymerization, and composition of the solvent/water polymerization medium. The solvents used were methanol, isopropanol, 1,4‐dioxane, cyclohexane, benzene, dimethyl formamide, and dimethyl sulfoxide. There were optimal concentrations of AIBN (5 mmol/L), MMA (8%), Fe²⁺ (0.1 mmol/L), Mn²⁺ (8 mmol/L), and Fe³⁺ (2 mmol/L). A polymerization medium of pH 2 and temperature of 70°C constituted the optimal conditions for grafting. The methanol/water mixture constituted the most favorable reaction medium for grafting MMA onto cotton fabric by using the Fe²⁺–cellulose thiocarbonate–AIBN redox system. MMA was superior to other monomers for grafting. The unmodified cotton cellulose showed very little tendency to be grafted with MMA compared with the chemically modified cellulosic substrate. A tentative mechanism for the grafting reaction was proposed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1261–1274, 2004     

Synthesis and characterization of a poly(acrylic acid)‐graft‐methoxy poly(ethylene oxide) comblike copolymer

A methoxy poly(ethylene oxide) (MPEO) grafted poly(acrylic acid) (PAA) comblike copolymer was synthesized by the direct condensation of MPEO onto the PAA backbone in the presence of dicyclohexyl dimethylcarbodiimide (DCC) and 4‐dimethylaminopyridine (DMAP). Its chemical structure was characterized by Fourier transform infrared and ¹H‐NMR spectroscopies. The effects of different catalysts, solvents, reaction temperatures, and reaction times on the grafting degree of the PAA‐g‐MPEO comblike copolymer were investigated. Compared to p‐toluene sulfonic acid, DMAP/DCC as a catalyst markedly increased the grafting degree. The optimum reaction conditions were a tetrahydrofuran/water mixture solvent, a reaction temperature of 50°C, and a reaction time of 168 h. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Intracellular pH‐sensitive dextran‐based micelles as efficient drug delivery platforms

As drug delivery systems, stimuli‐responsive polymer micelles hold great potential in cancer chemotherapeutics to improve therapeutic efficiency and eliminate organism adverse effects. Here, pH‐sensitive polymeric micelles based on dextran‐g‐benzimidazole were designed and used for intracellular anticancer drug delivery. The anticancer drug doxorubicin (DOX) was effectively loaded into the micelles via hydrophobic interactions. In vitro release studies demonstrated that the release of loaded DOX was greater and faster under acid conditions such as in carcinomatous areas (pH < 6.8) than in physiological conditions (pH 7.4). MTT assays and flow cytometric analyses showed that DOX‐loaded micelles had higher cellular proliferation inhibition towards HeLa and HepG2 cells than pH‐insensitive controls. These pH‐sensitive micelles with significant efficiency for intracellular drug release will be beneficial to the future of in vivo biomedical applications. © 2014 Society of Chemical Industry     

Swelling and drug release profile of poly(2‐ethyl‐2‐oxazoline)‐based hydrogels prepared by gamma radiation‐induced copolymerization

Poly(2‐ethyl‐2‐oxazoline) and acrylic acid were copolymerized in different compositions using γ‐rays‐induced polymerization and cross‐linking to obtain a series of pH‐sensitive hydrogels. The preparation parameters that may affect the copolymerization process such as the feed solution composition and irradiation dose were optimized. Swelling characteristics of the obtained polymeric hydrogels were evaluated. The results show the significant effects of the hydrogel composition, soaking time, and pH on the swelling equilibrium. The diffusion parameters obtained at pH 1 and 7 show the possibility of using the prepared hydrogels in the field of colon‐specific drug delivery systems. Ibuprofen as a model drug was loaded into (poly(2‐ethyl‐2‐oxazoline)/acrylic acid) copolymer hydrogel to investigate their drug release behavior at different pH values. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011