Synthesis and characterization of thermosensitive macroporous hydrogels for controlled drug delivery applications (original) (raw)
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Hemijska industrija, 2012
The aim of this paper is to propose equations for the diffusion of drugs for investigated drug/hydrogel systems using the parameters affecting the transport of drug through poly-(2-hydroxyethylmethacrylate/itaconic acid) (P(HEMA/IA)), poly(2-hydroxyethylacrylate/itaconic acid) (P(HEA/IA)), and poly(2-hydroxyethylmethacrylate/poly(alkyleneglycol) (meth)acrylates) (P(HEMA/BIS)) copolymeric hydrogels. Different monomer types, as well as the variable content of some components in hydrogel composition (the amount of ionizable comonomer (IA) and different type of nonionic poly(alkyleneglycol) (meth)acrylates), ultimately defined the pore size available for drug diffusion. The hydrogels synthesized ranged from nonporous to microporous, based on the classification in accordance to the pore size, and could be classified as hydrogels that contain ionic groups and hydrogels without ionic groups. The drugs selected for this study are bronchodilators-theophylline (TPH), fenethylline hydrochloride (FE), and antibiotic cephalexin (CEX). Results of in vitro drug release tests defined the release systems based on the drug type, as well as the type of hydrogel used. The diffusion coefficient of drugs and the restriction coefficient, λ, defined as the ratio of solute to "pore" radius (r s /r ζ ) that describes the ease of drug release from the gels, were used as factors that govern the release process.
Journal of Applied Polymer Science, 2010
Temperature sensitive polymer network porous hydrogels were developed with N-Isopropylacrylamide (NIPAAm) and AMPS (2-acrylamido-2-methyl-1-propanesulfonicacid), as well as with sucrose as porogen by crosslinking with hydrophilic crosslinker N,N1-methylenebisacrylamide (MBA). The temperature responsive behaviour, the swelling/deswelling kinetics of the hydrogels were investigated. The structural and morphological characterizations of the developed hydrogels were obtained from FTIR spectroscopy and scanning electron microscopy (SEM). The increment in the lower critical solution temperature (LCST) of NIPAAm hydrogels can be done with the help of AMPS and it is confirmed with differential scanning calorimetry (DSC) as well as temperature dependent swelling curves. The model cancer chemotherapy drug Doxorubicin (Dox) was loaded into theses hydrogels and the release studies as well as the released profiles of the drug showed that more than 8–54% of the loaded drug was released in the first half-an-hour at a buffer solution of 7.4 and the rest of the drug was released slowly. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Drug release with simultaneous dimensional changes from a new copolymeric hydrogel
Polymer, 1994
The diffusional behaviour of sodium salicylate (SSA) from a new chemically crosslinked copolymeric hydrogel of 2-hydroxyethyl methacrylate with N, N'-dimethyl-N-methacryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine is reported. The drug release into water was effected under sink conditions and the kinetics at 310 K were followed by continuous measurement of conductivity. A modified form of Fick's second law has been derived to take into account the dimensional changes of copolymer during drug release, which were measured photographically. The procedure was used to evaluate the diffusion coefficient D s for transport of SSA into water. The value of D s = 4.4 x 10-11 m 2 s-1 yielded over a range of drug loading is smaller than the load-dependent values obtained when allowance is not made for dimensional changes. The procedure has also been used to determine the diffusion coefficient for water into polymer.
Biomaterials, 2000
A comparative study on the drug release capacity of four water swellable polymeric systems was carried out by di!erential scanning calorimetry (DSC). The polymeric systems chosen were , -polyaspartahydrazide (PAHy) crosslinked by glutaraldehyde (GLU) (PAHy-GLU) or by ethyleneglycoldiglycidylether (EGDGE), (PAHy-EGDGE), polyvinylalcohol (PVA) crosslinked by glutaraldehyde (PVA-GLU) and , -poly(N-hydroxyethyl)-DL-aspartamide (PHEA) by gamma irradiation (PHEA-matrices). The degree of crosslinking for PAHy-GLU, PAHy-EGDGE and PVA-GLU samples was about 0.4 and 0.8. These hydrogels were characterized as free of drugs and were loaded with di#unisal (DFN) (+2.5% w/w). Di#unisal, a non-steroidal anti-in#ammatory drug, has been chosen as a model drug to be incorporated into polymeric matrices to follow the release processes of a drug from these hydrogels to a model membrane made by unilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC). Di!erential scanning calorimetry appears to be a suitable technique to follow the transfer kinetics of the drug from the controlled release system to the biomembrane model. The drug releases from all the considered polymeric hydrogels, were compared with the release observed from the drug solid form by examining the e!ects on the thermotropic behaviour of DPPC unilamellar vesicles. The release kinetics of the drug from hydrogels were followed at 25, 37 and 503C to evidence the in#uence of temperature on the drug release and on the successive transfer to biological membrane model. Particularly, it appears evident that the total amount of drug transferred and the release rate are a!ected by the polymer crosslinking degree (it increases with crosslinking decrease) as well as by the nature of crosslinking agent. In fact, the drug release pro"les from PAHy-GLU samples are more di!erentiated than those from PAHy-EGDGE. The e!ect of parameters correlating with the properties of starting polymer, such as water-a$nity, crystallinity, glass-to-rubber transition temperature and a$nity towards drug molecules, has been also evaluated.
Journal of Applied Polymer Science, 2019
A facile thermoresponsive injectable hydrogel is prepared from stearyl methacrylate (SMA) and N-isopropyl acrylamide (NIPAM) copolymers via reversible addition-fragmentation chain-transfer (RAFT) emulsion polymerization method. By regulating the content of the oil phase, emulsions with divergent properties are obtained. The yield stress and the viscosity results of the emulsions increase evidently as the initial content of the oil phase increase from 10 to 40%. The microstructures of 10% oil content sample (SN10) is seen as a dispersed particle whereas 20, 30, and 40% oil content samples (SN20, SN30, and SN40) appear as aggregated particles in a dilute solution that shows the microscopical phase transitions of the emulsions. Increasing the temperature from 15 to 45 C, phase separation takes place, the emulsions contract to squeeze the water. A sharp decrease in particle size is noticed when the temperature increase from 30 to 35 C. In this point, hydrophilic drug procaine is loaded and release experiments are conducted using thermoresponsive injectable hydrogel. The drug loading and release results are evaluated using the Weibull distribution model and the Fick's law of diffusion that precisely works out. A thermoresponsive injectable hydrogel offers an efficient, cost-effective, and scalable approach towards controlled release of drugs.
Combination of synthetic and natural polymers in hydrogel: An impact on drug permeation
Journal of Applied Pharmaceutical Science, 2016
Topical hydrogel preparations are applied on skin to obtain local or systemic action. NSAID's are non-steroidal drugs having excellent anti-inflammatory and analgesic activity but it produces GIT ulceration when used orally. To overcome that problem with oral formulations, many NSAID's are preferred to be administered by topical route. The present investigation is aimed to formulate the hydrogel of Diclofenac potassium with different ratio of Carbopol of different grades along with guar gum for application over the skin. Fourier transform Infrared (FT-IR) spectrophotometer has been used to notice drug-polymer interaction. After getting satisfactory combinations of polymers, hydrogel formulations of Diclofenac potassium were subjected to different physicochemical studies. Evaluation tests for visual appearance, pH, viscosity, spreadability, swelling index etc. were found satisfactory. To investigate the drug permeation kinetics and permeability coefficient from the goat abdominal skin, pieces of goat skin were fixed on the Franz diffusion cell, in a way that the upper surface of abdominal skin faced the donor chamber. The experiment was carried out with 2 gm of the drug loaded hydrogel spreaded on the skin surface at 32 o C in phosphate buffer pH-5.8. A distinct correlation between % swelling index and permeability coefficient of the formulations through goat abdominal skin has been observed. With increase in % swelling index over a period of 8 h the permeability coefficient decreased. It indicates that swelling of hydrogel forms a sticky, gelatinous mass that retards the permeation of Diclofenac potassium through goat abdominal skin. There are significant co relations between viscosity of hydrogel, % swelling index and permeation coefficient. It has been found that with increase in viscosity, permeability coefficient increased whereas permeability coefficient of drug decreased with increase in % swelling index of the formulations.
Journal of Controlled Release, 1990
Compression coating was investigated for use in preparing controlled release dosage forms having a polymer shell surrou~i~ a ~01~~ core. The purpose of the study was to deve~p a stud of me~ure flux and ~r~abili~ of water across the outer shell (coat) of the co~ress~n"~oated tablet. One half of the shell of the press-coated tablets was mounted on the platform of the receptor port of the Thomas diffusion cell by embedment in white petrolatum. T~Q cumulutive amount of tritium labeled water per square centimeter permeating across the barrier was plotted us time, and flux, lag time, diffusion coefficient and permeability were calculated from the steady-state slope. No difference was found water the ounce or inside of the ~rnbra~ was exposed to th.e donor phase. The lag time increased linearily and s~nifi~antly from 0.3 to 0.79 to 1.1 h with increasing shell thickness from 1.08 to 1.66 to 2.12 mm, respectively. Flux and permeability decrease hyperbolically with increasing shell thickness. Increasing hardness at constant shell amount significantly increases lug time and decreases flux and permeability. Compression-coating seems to be a viable technic for pre~rat~n of ~ont~l~d release drug delivery system with a wide range for ~j~tment of permeability.
Journal of Applied Polymer Science, 2012
Poly(N-isopropylacrylamide) (PNIPAM) hydrogels were simply prepared by free radical polymerization in different methanol-water mixture. A scanning electron microscopy study revealed that the freeze-dried hydrogels were macroporous. The swelling ratios in water at 20 C of the resulting hydrogels followed the order: X 0.43 >X 0.21 >X 0.76 % X 0.57 >X 0.31 >X 0.13 >X 0.06 >X 0 , where X m denotes a gel prepared in a methanol-water mixture with m mole fraction of methanol (x m ). Below the lower critical solution temperature, the swelling ratio values of all of the hydrogels gradually decreased with the increase in the temperature. The complete collapse of the PNIPAM chain of all the gels occurred at about 38 C, whereas the same was observed at about 35 C for the conventional gel prepared in water. The swelling ratio values of all the PNIPAM gels in the methanol-water mixtures with different x m values at 20 C passed through a minimum in the cononsolvency zone. The deswelling rates of the hydrogels decreased in the following order: X 0.43 > X 0.31 > X 0.21 > X 0.57 > X 0.76 % X 0.13 > X 0.06 > X 0 . The reswelling rates of these hydrogels decreased in the following order: X 0 > X 0.31 > X 0.06 % X 0.13 > X 0.76 > X 0.57 > X 0.21 > X 0.43 . The release rates of the Tramadol Hydrochloride drug at 37 C from the drug-loaded hydrogels were almost same for all of the hydrogels. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci