Copolymer Hydrogels Research Articles

Time Evolution of Local pH Around a Photo-Acid in Water and a Polymer Hydrogel: Time Resolved Fluorescence Spectroscopy of Pyranine.

In this work, we propose a new analysis of the time resolved emission spectra of a photo-acid, HA, pyranine (8-hydroxypyrene-1,3,6-trisulphonic acid, HPTS) based on time resolved area normalized emission spectra (TRANES). Presence of an isoemissive point in TRANES confirms the presence of two emissive species (HA and A- ) inside the system in bulk water and inside a co-polymer hydrogel [F127, (PEO)100 -(PPO)70 -(PEO)100 ]. We show that following electronic excitation, the local pH around HPTS, is much lower than the bulk pH presumably because of ejection of proton from the photo-acid in the excited state. With increase in time, the local pH increases and reaches the bulk value. We further, demonstrate that the excited state pKa of HPTS may be estimated from the emission intensities of HA and A- at long time. The time constant for time evolution of pH is ∼630 ps in water, ∼1300 ps in F127 gel and ∼4700 ps in CTAB micelle. The location and local viscosity sensed by the probe is ascertained using fluorescence correlation spectroscopy (FCS) and fluorescence anisotropy decay. The different values of the local viscosity reported by these two methods are reconciled.

Synthesis and characterizations of zwitterionic copolymer hydrogels with excellent lubrication behavior

Abstract Various studies on hydrogel applications as cartilage substitutes and artificial joints have been previously conducted. In this study, a copolymer hydrogel comprising zwitterionic sulfobetaine methacrylate (SBMA) and 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers is synthesized in an aqueous system via free-radical polymerization. A P(MPC-co-SBMA) copolymer hydrogel network is formed via the additional polymerization of the alkane carbon–carbon double bond from the combination of MPC and SBMA polymer chains using ethylene glycol dimethacrylate (EGDMA) as the crosslinker. Introduction of MPC in the PSBMA hydrogel under water lubrication improved the compressive stress by almost double and considerably lowered the coefficient of friction (COF) to approximately 0.011. This phenomenon was attributed to the fact that MPC could intertwine with SBMA to increase the crosslink density of the hydrogel and preferentially adhere to the water to reduce the adhesion of the contact between hydrogels, leading to an intertwined copolymer network structure with excellent load-bearing capacity and superior hydration lubrication capability. This study might provide potentially useful information relating to cartilage replacement applications requiring high mechanical strength and excellent friction behavior.

Mechanical Properties and Moisture Transport Behavior of Acid-Sensitive Hydrogels

Thin hydrogel films containing the acid sensitive cross-linker 2,5-dimethyl-2,5-hexanediol dimethacrylate (DHDMA) were synthesized as part of a larger project to create protective layers against chemical and biological (CB) threats. In order to operate efficiently as fabric coatings, the mechanical and moisture vapor transport properties of these materials must be understood. The hydrogels were composed primarily of poly(ethylene glycol) dimethacrylate (PEGDMA) and 2-hydroxyethyl methacrylate (HEMA) and were prepared by free radical cross-linking polymerization. The influence of different compositions of DHDMA, PEGDMA, and HEMA on the moisture vapor transmission rate (MVTR), mechanical properties, and swelling properties of PEGDMA/DHDMA/HEMA copolymer hydrogels has been investigated. The characterization by Fourier transform infrared (FTIR) spectroscopy confirmed the presence of all monomers used in the gel structure. The hydrogels showed high MVTR, which are comparable to the widely accepted breathable m...

Radiation development of pH-responsive (xanthan-acrylic acid)/MgO nanocomposite hydrogels for controlled delivery of methotrexate anticancer drug

Nanocomposite hydrogels composed of magnesium oxide (MgO) and natural polymer-based copolymer of Xanthan gum (Xan) and acrylic acid (AAc) were prepared using radiation-induced copolymerization and crosslinking technique to be used as a drug delivery system. MgO nanoparticles were synthesized using sol- gel method. FTIR, XRD, UV-vis and TEM analysis revealed the successful preparation of MgO nanoparticles. The size of MgO nanoparticles was found to be 6.6 nm. FTIR data confirmed the incorporation of MgO within the (Xan-AAc) copolymer hydrogel. The presence of MgO nanoparticles slightly decreases the gelation degree and on contrary the swelling degree and network porosity was enhanced. (Xan-AAc)/MgO nanocomposites show typical pH-dependent swelling behavior Moreover, the swelling kinetics showed that all the samples under investigation possess Fickian at pH1 and non-Fickian at pH7. Methotrexate (MTX) as model for anticancer drugs was used to evaluate the potential efficiency of the obtained (Xan-AAc)/MgO nanocomposites as drug carrier. Incorporation of MgO into (Xan-AAc) hydrogel improves the drug loading efficiency and enhances the (MTX) release to reach maximum in the simulated intestine medium (pH7). The drug release profile came in a good agreement with swelling results which recommend the (Xan-AAc)/MgO nanocomposite hydrogels as potential targeted drug delivery system.

Study on the influence of inductive groups on the performance of carboxylate-based hydrogel polymer network

We report study on the effect of Br and CH3 inductive groups on the loading capacity of carboxylate-based hydrogel adsorbent. Synthesized sodium acrylate (NaAc) and 2-Bromoacrylic acid (BrAc) copolymer hydrogels for metal ion capture were characterized using FTIR, UV–Vis, 13C NMR, and DSC methods for structural and functional properties. Both FTIR and UV–Vis spectra indicated formation of a charge transfer complex between Br, CH3 groups and the carbonyl (C═O) group whereas solid-state NMR evidenced Br group appearance as an appendage on hydrogel backbone. By incorporating Br group on the hydrogel matrix and consequently exploiting the high electronegativity potential and inductive effect chemistry of this group, there was a significant increase in dissociation of H+ ions and hence higher loading capacity of carboxylate group. This facilitated higher ion exchange ability, resulting in up to 4 times increase in adsorption capacity during adsorption from multi-element metal ion competitive solution. Separately, when applied on single ion non-competitive solution, its adsorption capacity on vanadium increased three-fold from 119 mg/g to 373 mg/g due to the effect of Br group. However, the CH3 had a negating effect instead lowering the adsorption capacity (below 119 mg/g); while also caused lower swelling ratio of carboxylate-functionalized hydrogel adsorbents.

Metakrilamid Esaslı Polimerik Hidrojellerin Denge Şişme Çalışmaları

In this study, it was aimed that produce new polymeric hydrogels and that investigate the equilibrium swelling properties. Chemically crosslinked copolymeric hydrogels, composed of methacrylamide (MAAm) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were prepared via free radical copolymerization method. The obtained copolymeric hydrogels were characterized with FT-IR analysis and SEM techniques. In addition, swelling tests 25 oC were applied to all the synthesized samples and swelling characterization studies were performed. The influences of reaction variables such as monomer/co-monomer composition, crosslinker amount on swelling properties of hydrogels were investigated. When the swelling results are evaluated; It was observed that all polymeric samples showed different swelling and diffusion properties depending on their composition.

Preparation and Physicochemical Characterization of Dual Responsive and Chemically Modified Cellulose Based Copolymer Hydrogels

Abstract This research work is based on the preparation and physicochemical characterization of Poly(N-isopropylacrylamide)–Cellulose–Poly(Acrylic acid) [PNIPAAm–Cellulose–PAAc] based terpolymer hydrogels. The free radical polymerization reaction was initiated by the presence of ammonium persulphate (APS) and crosslinking between different monomers was occurring through N,Nl- Methylene bis-acrylamide (MBA). Confirmation of polymerization process was done by FT-IR and UV-visible spectroscopy. The prepared hydrogels were further characterized by different physicochemical techniques like rheology, Ostwald viscometry and dynamic light scattering (DLS). The effect of external stimuli like temperature, pH and composition of the samples on the physicochemical behavior was also carried out by dynamic rheology, swelling measurement and DLS. Various other properties like elasticity, shear stress, shear strain, loss modulus, storage modulus and complex viscosity was investigated by rheology. DLS was used to trace the size and swelling behavior of the samples. From the results obtained it was found that all the microgel samples are stimuli responsive and most of their physicochemical properties were prominently varying while changing the internal as well as the external experimental variable. These changes in physicochemical behavior of the gel can be attributed to two possibilities; the change in the hydrophobic character of gel (PNIPAAm) with temperature and also to the weakening of intermolecular hydrogen bonds with increase in temperature. As a result of this the PAA chains may undergo a transition from a compact conformation to an expanded coil conformation, resulting in the swelling of the hydrogels.

Tough Triblock Copolymer Hydrogels with Different Micromorphologies for Medical and Sensory Materials

Tough triblock copolymer hydrogels with microstructures of sphere, cylinder, and laminae were constructed using a newly developed “drying and swelling” method without changing the chemical structures of their monomeric units. These tough triblock copolymer hydrogels commonly showed high fracture stress of ∼10 MPa but exhibited varied elastic moduli depending on their microstructures. Furthermore, the constructed laminar gel formed pH-sensitive photonic gel at the base conditions, providing the gel application with potential as a sensor. Given their high toughness, biocompatibility, and tunable modulus, this study helps expand the potential application of amphiphilic block copolymer hydrogels for medical and industrial use.

Sustained co-delivery of gemcitabine and cis-platinum via biodegradable thermo-sensitive hydrogel for synergistic combination therapy of pancreatic cancer

Pancreatic cancer is one of the most devastating cancers with poor prognosis and no significant change in the survival rate over the past decades. Localized targeted drug delivery through interventional endoscopic ultrasonography-guided fine-needle injection (EUS-FNI) is an attractive and minimally invasive strategy for inoperable pancreatic cancer. An injectable in-situ formed long-lasting drug delivery system is a promising alternative for the localized treatment of pancreatic cancer via EUS-FNI. Here, a biodegradable thermo-sensitive copolymer hydrogel for the co-delivery of anticancer agents gemcitabine (GEM) and cis-platinum (DDP) was developed. This hydrogel is a free flowable liquid at room temperature that changes into a semi-solid hydrogel following injection in response to the physiological temperature. Both in vitro and in vivo drug release behaviors indicate sustained drug release of this delivery system. Synergistic cellular proliferation inhibition and desirable apoptosis promotion have been found when pancreatic cancer Bxpc-3 cells were co-cultured with this GEM-DDP/hydrogel system. After a single intratumoral injection, the dual-drug loaded hydrogel formulation exhibited superior anti-tumor efficacy and minimized systemic side effect on pancreatic cancer xenograft mouse model in comparison to the intravenously injected free GEM and DDP combination. In addition, a strong synergistic therapeutic effect of the GEM-DDP/hydrogel system against pancreatic cancer has been found in vitro and in vivo compared to the single-drug loaded hydrogel composites. The obtained findings suggest this developed thermo-sensitive copolymer hydrogel system as a potential universal carrier for the localized targeted delivery of multi-drugs, for use in a variety of inoperable solid tumors.

Synthesis and evaluation of injectable thermosensitive penta-block copolymer hydrogel (PNIPAAm-PCL-PEG-PCL-PNIPAAm) and star-shaped poly(CL─CO─LA)-b-PEG for wound healing applications.

Loss of skin integrity due to injury, burning, or illness makes the development of new treatment options necessary. Skin tissue engineering provides some solutions for these problems. The potential of a biodegradable star-shaped copolymer [Poly(CL─CO─LA)-b-PEG] and penta-block copolymer hydrogel (PNIPAAm-PCL-PEG-PCL-PNIPAAm) was assessed for skin tissue engineering applications. Two copolymers were synthesized for cellular culture scaffolds and their mechanical properties were compared. The resulting star-shaped copolymer and thermosensitive penta-block copolymer were characterized using Fourier transform infrared and nuclear magnetic resonance spectroscopy. The crystallizability of the two copolymers wasanalyzed using X-ray diffraction. The resulting thermosensitive penta-block copolymer was evaluated by differential thermal analysis, differential scanning calorimetry and thermogravimetric analysis. Scanning electron microscopy and in vitro degradation of the polymer network in phosphate buffer solutions (pH 7.4) at 37°C were also examined. The pore size of the gels was calculated with Image Analyzer software. Finally, the cytotoxic, morphological, and gene expression effects of copolymers on the skin fibroblast were evaluated. The experiments showed that the PNIPAAm-PCL-PEG-PCL-PNIPAAm polymer with the right composition and the expected molecular weight wasachieved. The hydrogel had less crystallizability compared with its precursors. The resulting thermosensitive hydrogel had a three-dimensional structure with interconnected pores that mimicked the extracellular matrix. The control of the degradability rate can be possible by weight percent changes. The pore size correlated with the polymer concentration in aqueous solution and the pore sizes of the 20 wt% hydrogel were better for fibroblast cultivation than those of the 10 wt% hydrogel. Cell proliferation on the 20% gel was more than that of the 10% gel. The hydrogel not only preservedthe viability and phenotypical morphology of the entrapped cells but also stimulatedthe initial cell-cell interactions and proliferation of fibroblasts. The hydrogel did not influence cell conformation and this property of the polymer underlinedits safety. Cells seeded on this copolymer showed a normal and spearshapeand formed a focal adhesion with the hydrogel surface. Notably, the hydrogel increased collagen I α1 and collagen III mRNAs expression. Due to the low molecular weight and poor mechanical strength of the star-shaped copolymer, it was not considered for fabricationof the scaffolds for wound healing. The biodegradable, biocompatible, injectable and thermosensitive PNIPAAm-PCL-PEG-PCL-PNIPAAm hydrogel in 20 wt% demonstrated a desirable potential for future application as a cell scaffold in skin tissue engineering and wound healing.

Dual-responsive copolymer hydrogel as broad-spectrum adsorbents for metal ions

A copolymeric hydrogel (PEGMA) with poly(ethylene glycol) methyl ether acrylate (PEGA), 2-methoxyethyl acrylate (MEA) and acrylic acid (AA) was synthesized in this study. The obtained PEGMA hydrogel exhibited sensitive response to pH and temperature and showed excellent adsorption properties for many metal ions, such as Fe(Ⅲ), Pb(Ⅱ), Zn(II), Ni(II), Mn(II) and Co(II), etc. Fe(Ⅲ) and Pb(Ⅱ) were selected to study thermodynamics and kinetics. The adsorption process followed pseudo-second-order kinetics equation. The adsorption isotherms could be described by Freundlich isotherm models. The maximum adsorption amount was calculated to be 195.43 (Fe3+) and 176.06 (Pb2+) mg/g. Besides, using the thermal and pH responsiveness, the PEGMA hydrogels can quickly release the adsorbed molecules with control. The heavy metal ions loaded PEGMA hydrogels could also be easily regenerated by diluted hydrochloric acid and still keep a major adsorption capacity. After five cycles, the adsorption ability remained more than 90% of the original PEGMA. Thus, the PEGMA hydrogels may be new high-performance and environment friendly material for metal pollution treatment with promising developmental potential.

Self‐Assembled Acrylic ABA Triblock Copolymer Hydrogels with Various Block Compositions: Water Absorbency, Rheology, and SAXS

AbstractA series of well‐defined symmetric poly(methyl methacrylate)‐b‐poly(sodium methacrylate)‐b‐poly(methyl methacrylate) (PMMA‐b‐PSMA‐b‐PMMA) triblock copolymers with various block compositions is synthesized. The amphiphilic ABA triblock copolymers form polyelectrolyte hydrogels in water by self‐assembly. The hydrophobic PMMA endblocks act as physical cross‐links in the form of frozen micelles, while the hydrophilic PSMA midblocks span the 3D network. The influence of various synthetic parameters on the self‐assembly and the macroscopic properties of these hydrogels is systematically investigated by water absorbency, oscillatory shear rheology, and small‐angle X‐ray scattering. The polymer concentration during the hydrogel formation affects the ratio between looping and bridging chains. The number of MMA units per endblock (nA) determines the size and the relaxation rates of the physical cross‐links and thus, the mechanical stability of the hydrogels. More SMA units in the midblock (nB) increase the water absorbency, while the mechanical moduli decrease. Even lower G‐moduli are achieved by partly exchanging the symmetric ABA triblock with AB diblock copolymers, which can only form non‐elastic dangling ends.

Injectable Vaginal Hydrogels as a Multi-Drug Carrier for Contraception

Injectable intravaginal hydrogels could deliver drugs systemically without hepatic first pass effect. This paper focuses on the contraceptive function of an injectable temperature-sensitive four-arm star-shaped poly(D,L-lactic-co-glycolic acid)-b-methoxy poly(ethylene glycol) (4sPLGA-mPEG) block copolymer hydrogels as a carrier of three drugs. In vitro controlled release profiles were investigated via HPLC, and it showed that the cumulative release amounts of indomethacin (IMC), gestodene (GSD), and ethinyl estradiol (EE) from copolymer hydrogels could be regulated by adjusting the lactide/glycolide (LA/GA) mol ratio. In addition, in vitro release profiles of IMC, GSD, and EE well corresponded to Higuchi model. The acute toxicity of copolymer hydrogels loaded with different dosage contents multi-drug was evaluated in vivo. As to the high dosage group, the uterus was hydropic at day 1 and ulcerated at day 5, followed with intestinal adhesion. Regarding the middle dosage group, no festering of tissues was observed and, blood coagulum existed in the uterus at different days. For low dosage group, no significant tissue necrosis was found. Finally, the antifertility experiments confirmed that hydrogels loaded with the multi-drug had an excellent contraceptive effect. The above results indicated that injectable copolymer hydrogel as a multi-drug carrier was promising as a novel contraception method.

Hierarchical assembly in PLA-PEO-PLA hydrogels with crystalline domains and effect of block stereochemistry

Understanding the development of microstructure (e.g., structures with length scales roughly 0.5–500 μm) in hydrogels is crucial for their use in several biomedical applications. We utilize ultra-small-angle neutron scattering (USANS) and confocal microscopy to explore microstructure of poly(lactide)-poly(ethylene oxide)-poly(lactide) (PLA-PEO-PLA) triblock copolymer hydrogels with varying l/d-lactide ratio. We have previously found that these polymers self-assemble on the nanoscale into micelles. Here, we observe large-scale structures with diverse morphologies, including highly porous self-similar networks with characteristic sizes spanning approximately 120 nm–200 μm. These structural features give rise to power-law scattering indicative of fractal structures in USANS. Mass fractal and surface fractal structures are found for gels with l/d ratios of 80/20 and 50/50, respectively. Confocal microscopy shows microscale water-filled channels and pores that are more clearly evident in gels with a higher fraction of l-lactide in the PLA block as compared to the 50/50 hydrogels. Tuning block stereochemistry may provide a means of controlling the self-assembly and structural evolution at both the nanoscale and microscale, impacting application of these materials in tissue engineering and drug delivery.

Preparation And Characterization of Magnetic Nanocomposite Based on Gum Arabic/2-Hydroxyethylmethacrylate Using Gamma Irradiation For Use In Biomedical Application

Magnetic nanoparticles were prepared from gum arabic (GA), 2-hydroxyethylmethacrylate (HEMA) copolymer hydrogel using gamma irradiation. The factors affecting on the preparation of (GA/HEMA) copolymer hydrogel and the magnetic nanocomposite of (GA/HEMA)-(Fe3O4) such as irradiation dose, copolymer composition, copolymer concentration and magnetite concentration were investigated. The swelling property of the prepared hydrogels was studied and the results showed that the swelling percent increases with increasing PH and reaching equilibrium swelling at 6 h. The obtained hydrogel and its magnetic nanocoposites were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and Transmission electron microscope (TEM). The presence of Fe3O4 inside the GA/HEMA-Fe3O4 nanocomposites was confirmed by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). Magnetic properties were characterized by Vibrating sample magnetometer (VSM). Finally, the drug loading and in vitro release properties of the (GA/HEMA) copolymer hydrogel and its magnetic nanocomposites were also evaluated using endoxan as an anticancer drug model. The results showed that, the optimum endoxan drug release was 97% from (GA/HEMA)-(Fe3O4) nanocomposite during 210 min. Thus, (GA/HEMA)-(Fe3O4) nanocomposite could be used for localized drug delivery for endoxan drug in neutral environment of the intestine.

Venlafaxine-loaded sustained-release poly(hydroxyethyl methacrylate-co-itaconic acid) hydrogel composites: their synthesis and in vitro/in vivo attributes

Hydrogels have potential applications as sustained-release drug delivery systems, as an example in treatment of major depressive disorders. This paper reports some works carried out to obtain a new type of copolymeric hydrogel for an anti-depressant drug. The copolymerization of itaconic acid, hydroxyethyl methacrylate (HEMA), and tetraethyleneglycol dimethacrylate was performed. The gels were evaluated for swelling, diffusion coefficient, drug incorporation, in vitro dissolution, and in vivo performance in rabbits after oral administration. The pharmacokinetic parameters like bioavailability, Cmax and Tmax were calculated for hydrogels in comparison to oral solution containing equivalent amount of venlafaxine. The HEMA-based matrices showed negligible swelling and release rate of venlafaxine, which were also very low in a buffer of pH 1.2. However, both the swelling and release rate of venlafaxine were faster at high pH (6.5 and 7.5). The Tmax of the formulation with the highest swelling and release rate (T1) were found at 600 min compared to that at 180 min for oral solution having equivalent quantity of venlafaxine. AUC0–∞ for oral hydrogel was 2.1 times greater than that for oral solution of venlafaxine. Similarly, MRT for hydrogel was 3.1 times more than that for oral solution. However, Cmax for oral cross-linked hydrogel composite was significantly lower than that for equivalent amount of oral drug solution. The synthesized hydrogel composites showed a promising ability for sustained release of venlafaxine both in vitro and in vivo. It was found that venlafaxine delivery through oral route was practical.

Development of a gelatin‐g‐poly(acrylic acid‐co‐acrylamide)–montmorillonite superabsorbent hydrogels forin vitrocontrolled release of vitamin B12

ABSTRACTGelatin (Ge)‐g‐poly(acrylic acid‐co‐acrylamide) and montmorillonite (MMT)‐clay‐based nanocomposite hydrogels were fabricated to study the controlled release of vitamin B12. Polymeric hydrogels were characterized with Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). FTIR spectroscopy confirmed the grafting of partially neutralized acrylic acid on a Ge backbone. The incorporation of MMT fillers inside the nanocomposite hydrogels and their increased crystallinity were established by XRD analysis. The rough surface morphologies of the composite hydrogels shown by SEM resulted from the assimilation of MMT inside the same. TEM confirmed the formation of nanosized composites. The average length and width of the MMT platelets were found to be 184.37 and 20.48 nm, respectively. The maximum swelling of the hydrogel was 375 g/g, and the results were established with Design‐Expert software. The biodegradability of the nanocomposite increased in comparison to that of the copolymer hydrogel. Biocompatibility and cytotoxicity studies were also performed. During different time intervals, the controlled release of vitamin B12in artificial gastric fluid (AGF) and artificial intestinal fluid (AIF) was evaluated with a UV–visible spectrophotometer; this resulted in different controlled release curves. The release in AGF was 42%, and in AIF, the cumulative release was 80% over 6 h. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 47596.

Active visualized solvent sensor based on copolymer hydrogel photonic crystals containing white LEDs

This study demonstrated the achievement of rapid chemical solvent detection by a copolymer hydrogel photonic crystal sensor (CHPCS) created by a simple infiltration of the copolymer hydrogel precursor inside the voids of three-dimensionally opal photonic crystal templates. CHPCS with strong mechanical strength was used as copolymer poly(HEMA-co-MMA-co-NVP) hydrogel and composite poly(St-co-AA-co-MMA) sub-microspheres. CHPCS was immersed in different chemical solvents, including alcohols (hydroxyl compounds) and acetone (carbonyl compounds). The interlayer spacing of CHPCS was swollen and exhibited optical diffraction, which could be detected by the optical measurements and theoretical prediction based on the Bragg diffractive theory. We proposed and demonstrated that CHPCS combined with white LEDs could serve as active naked eye detection solvent sensors that further exhibit great potential as real-time monitoring detectors for chemical solvents.

Electrically Triggered Transdermal Drug Delivery Utilizing Poly(Acrylamide)-graft-Guar Gum: Synthesis, Characterization and Formulation Development

Objective: The study aimed to prepare electrically-triggered transdermal drug delivery systems (ETDS) using electrically responsive polyacrylamide-graft-gaur gum (PAAm-g-GaG) copolymer. Methods: The PAAm-g-GaG copolymer was synthesized by adopting free radical polymerization grafting method. This PAAm-g-GaG copolymer hydrogel acts as a drug reservoir and blend films of Guar Gum (GaG) and Polyvinyl Alcohol (PVA) were included as Rate Controlling Membranes (RCM) in the system. The PAAm-g-GaG copolymer was characterized by FTIR, neutralization equivalent values, thermogravimetric analysis and elemental analysis. Results: On the basis of results obtained, it is implicit that the drug permeation decreased with an increase in the concentration of glutaraldehyde and RCM thickness; while drug permeation rate was increased with increasing applied electric current strength from 2 to 8 mA. A two fold increase in flux values was observed with the application of DC electric current. An increase in drug permeation was witnessed under on condition of electric stimulus and permeation was decreased when electric stimulus was "off". The skin histopathology study confirmed the changes in skin structure when electrical stimulus was applied. Conclusion: The electrically-sensitive PAAm-g-GaG copolymer is a useful biomaterial for transdermal drug delivery application.

Investigation of a novel thermogelling hydrogel for a versatility of drugs delivery

The P(CL-PDO)-PEG-(P(CL-PDO)(PECP) copolymer hydrogel is an attractive thermogelling material for practical applications due to the fast dissolution of the copolymer in water and good stability of the resultant sol solution that is beneficial for guest matter mixing. In this paper, the degradation properties and drug release behavior of the hydrogel loaded with various types of drugs were evaluated. The integrity of the PECP hydrogel could preserve for 2 weeks and became viscous liquid after degradation time of 21 weeks. With the degradation time, both the molecular weight and weight loss of the hydrogel decreased gradually. NMR analysis of the degraded products indicated that the chain breaking of the copolymer mainly occurred within the sequence structures of PDO-PDO or PDO-PCL, implying the acceleration effect of PDO unit to the degradation of hydrogel. Three distinct types of drugs including small molecular hydrophobic, small molecular hydrophilic and hydrophilic macromolecular drugs were loaded into the PECP hydrogel to evaluate their release profiles. The result showed that the releasing periods for macromolecular protein or hydrophobic drug were extended to more than one month. Since these two types of drugs are loaded within different regions of the hydrogel due to their different hydrophobic/hydrophilic nature, the PECP hydrogel is expected to develop injectable system loaded with a versatility of drugs or guest matter for synergetic effect.