Swelling Properties of Chemically Crosslinked Poly(acrylamide-co-maleic acid) Hydrogels

Amide modified cellulose-g-poly acrylic acid as a supple superabsorbent for water retention and soil conditioner

Acrylamide has high hydrophilic properties due to the presence of hydrophilic amide functional groups and is frequently used to synthesize superabsorbents. However, the toxic and carcinogenic properties of acrylamide have caused environmental concerns. The main goal of this paper is the synthesis of superabsorbent with high water absorption from biodegradable and biocompatible cellulose polymer containing amide groups in the backbone of it instead of grafting harmful acrylamide monomers to cellulose. The supple superabsorbent of amide-2,4 modified cellulose-g-poly acrylic acid (Am-2,4 modified cellulose-g-poly (AA)) to reduce water consumption in agriculture and facilitate rooting and root penetration in clay was used. To investigate the effectiveness of superabsorbent in agriculture, its water retention in treated soil (0.2 %) with different temperatures, pHs, and soil textures (sandy loam (SL), sandy clay loam (SCL), clay loam (CL), and loam (L)) was studied. Also, water retention in SCL soil in 2 cycles showed good results. Furthermore, the study includes the optimization of the parameters affecting the water absorption capacity of the superabsorbent, which leads to the absorption of 1253.20 ± 49.67 g/g in distilled water, 86.88 ± 13.36 g/g in 1.0 wt% NaCl solution, and 395 ± 14.86 g/g in tap water under optimal conditions.

Hydrophobic association-improved multi-functional hydrogels with liquid metal droplets stabilized by xanthan gum and PEDOT:PSS for strain sensors

The synthesis of liquid metal-infused hydrogels, typically constituted by polyacrylamide networks crosslinked through covalent bonds, often encounters a conundrum: they exhibit restricted extensibility and a diminished capacity for self-repair, owing to the inherently irreversible nature of the covalent linkages. This study introduces a hydrophobically associated hydrogel embedding gallium (Ga)-droplets, realized through the in situ free radical copolymerization of hydrophobic hexadecyl methacrylate (HMA) and hydrophilic acrylamide (AM) in a milieu containing xanthan gum (XG) and PEDOT:PSS, which co-stabilizes the Ga-droplets. The Ga-droplets, synergistically functioning as conductive agents alongside PEDOT:PSS, also expedite the hydrogel's formation. The resultant XG/PEDOT:PSS-Ga-P(AM-HMA) hydrogel is distinguished by its remarkable extensibility (2950 %), exceptional toughness (3.28 MJ/m3), superior adherence to hydrophobic, smooth substrates, and an innate ability for hydrophobic-driven self-healing. As a strain sensing medium, this hydrogel-based sensor exhibits heightened sensitivity (gauge factor = 12.66), low detection threshold (0.1 %), and robust durability (>500 cycles). Furthermore, the inclusion of glycerol endows the XG/PEDOT:PSS-Ga-P(AM-HMA) hydrogel with anti-freezing properties without compromising its mechanical integrity and sensing acumen. This sensor adeptly captures a spectrum of human movements, from the nuanced radial pulse to extensive joint articulations. This research heralds a novel approach for fabricating multifaceted PAM-based hydrogels with toughness and superior sensing capabilities.

Formulation of pH-responsive highly swellable hydrogel scaffolds for controlled release of tramadol HCl: characterization and biocompatibility evaluation

Introduction: The objective of current project was to formulate a system for controlled delivery of Tramadol HCl (TRD), an opioid analgesic used in the treatment of moderate to severe pain. Methods: For this purpose, a pH responsive AvT-co-poly hydrogel network was formulated through free radical polymerization by incorporating natural polymers i.e., aloe vera gel and tamarind gum, monomer and crosslinker. Formulated hydrogels were loaded with Tramadol HCl (TRD) and evaluated for percent drug loading, sol-gel fraction, dynamic and equilibrium swelling, morphological characteristics, structural features and in-vitro release of Tramadol HCl. Results and Discussions: Hydrogels were proved to be pH sensitive as remarkable dynamic swelling response ranging within 2.94g/g-10.81g/g was noticed at pH 7.4 as compared to pH 1.2. Percent drug loading was in the range of 70.28%-90.64% for all formulations. Thermal stability and compatibility of hydrogel components were validated by DSC analysis and FTIR spectroscopy. Controlled release pattern of Tramadol HCl from the polymeric network was confirmed as maximum release of 92.22% was observed for over a period of 24 hours at pH 7.4. Moreover, oral toxicity studies were also conducted in rabbits to investigate the safety of hydrogels. No evidence of any toxicity, lesions and degeneration was reported, confirming the biocompatibility and safety of grafted system.

Maleic acid as an important monomer in synthesis of stimuli-responsive poly(acrylic acid-co-acrylamide-co-maleic acid) superabsorbent polymer

Poly(acrylic acid-co-acrylamide-co-maleic acid) (p(AA-co-AM-co-MA)) superabsorbent polymer was synthesized from acrylic acid (AA), acrylamide (AM), and maleic acid (MA) via free radical copolymerization. Results showed the presence of maleic acid in structure of superabsorbent has the key and superior role in creating a smart superabsorbent. The structure, morphology, and strength of the superabsorbent were characterized using FT-IR, TGA, SEM, and rheology analysis. The effect of different factors was investigated to determine the ability of water absorbency of the superabsorbent. According to optimized conditions, the water absorbency capacity of the superabsorbent in distilled water (DW) was 1348 g/g and in a solution containing 1.0 wt.% NaCl (SCS) was 106 g/g. The water retention ability of the superabsorbent was also investigated. The kinetic swelling of superabsorbent was identified by Fickian diffusion and Schott's pseudo-second-order model. Furthermore, the reusability of superabsorbent was studied in distilled water and saline solution. The ability of superabsorbent was investigated in simulated urea and glucose solutions, and very good results were obtained. The response ability of the superabsorbent was confirmed by swelling and shrinking behavior against changes of temperature, pH, and ionic strength.

Formulation, In Vitro Evaluation, and Toxicity Studies of A. vulgaris-co-AAm Carrier for Vildagliptin

This study investigated the use of Artemisia vulgaris L. seed mucilage as a new excipient for sustained delivery of Vildagliptin. Copolymeric carrier of A. vulgaris seed mucilage-co-AAm was devised by using acrylamide (AAm) as a monomer, methylene-bis-acrylamide (MBA) as a crosslinker, and potassium persulfate (KPS) as an initiator through free radical polymerization. Different formulations of A. vulgaris-co-AAm were devised by varying contents of polymer, monomer, crosslinking agent, initiator, and reaction temperature. Copolymeric structures were characterized through XRD analysis, Fourier transform infrared (FTIR) spectroscopy, TGA and DSC analysis, and scanning electron microscopy. Porosity, gel fraction, and Vildagliptin loading capacity of copolymers were also established. Swelling and in vitro drug release studies were conducted. XRD evaluation showed the alteration of the crystalline structure of Vildagliptin into an amorphous form. FTIR analysis confirmed the successful grafting of AAm to A. vulgaris seed mucilage backbone. Porosity was increased with increasing polymer concentration and reaction temperature while it was decreased with an increasing amount of AAm, MBA, and KPS. Gel content was decreased with increasing polymer concentration and reaction temperature while it was increased with an increasing amount of AAm, MBA, and KPS. Acute oral toxicity of copolymeric network was done in animal models to evaluate the safety. Copolymers showed the same swelling behavior at all pH 1.2, 4.5, 6.8, and 7.4. Vildagliptin release from copolymer showed a cumulative trend by increasing polymer content and reaction temperature, while a declining trend was observed with increasing contents of monomer, crosslinking agent, and initiator. Sustained release of Vildagliptin was observed from copolymers and release followed the Korsmeyer-Peppas model. From the acute oral toxicity studies, it is evident that newly synthesized copolymeric carriers are potentially safe for eyes, skin, and vital organs.

Fabrication, characterization and comparison of α-arbutin loaded dissolving and hydrogel forming microneedles

In this study, polyacrylic acid-co-maleic acid (PAMA) and polyvinyl alcohol (PVA) (1:4) were used to fabricate dissolving microneedles (DMNs) and hydrogel forming microneedles (HMNs) which incorporated α-arbutin. Αlpha-arbutin is commonly used as a skin lightening agent. However, it has poor penetration ability due to its hydrophilic properties. The purpose of this study was to compare the permeation of α-arbutin into the skin using DMNs and HMNs. Both types of microneedles (MNs) were sharp, strong with elegant appearance and approximately 100% penetrated the neonatal porcine skin. All needles of α-arbutin loaded DMNs were completely dissolved within 45 min, whereas maximum swelling of HMNs was observed at 4 h. In vitro permeation studies showed that α-arbutin loaded DMNs and HMNs provided significantly about 4.5 and 2.8 times, respectively, greater α-arbutin permeability than gel and commercial cream (P < 0.05). In vivo study also showed high intradermal delivery of α-arbutin levels using DMNs (5.33 µg/mL) and HMNs (1.47 µg/mL) when compared to that of commercial cream 0.15 µg/mL. Moreover, the micro-holes caused by applying MNs can reseal within 1 h. MNs were also stable at 25 °C for 3 months. The results suggested that DMNs and HMNs developed have a promising platform for transdermal delivery.

Evaluation of Thermally Crosslinked Poly(Acrylic Acid-Co-Maleic Acid) (PAMA)/Poly(Vinyl Alcohol) (PVA) Microneedle Arrays

This study aimed to evaluate the optimal conditions for crosslinked of PAMA/PVA microneedle (MN) arrays. Poly (acrylic acid-co-maleic acid) (PAMA)/poly (vinyl alcohol) (PVA) MN arrays were fabricated for the first time using the micromolding technique. The PAMA/PVA MN arrays at the polymer ratio of 1:4 were sharp, homogenous and perfectly formed with an elegant appearance. The successfully crosslinking MN arrays were determined using FTIR and water insolubilization. The results showed that increasing the crosslinking temperature and time, the degree of crosslinking also improved, which results in a decline in water uptake. The optimal crosslinking condition for PAMA/PVA MN arrays was 130°C for 1 h. Moreover, the highest swelling was observed from crosslinked PAMA/PVA MN arrays at 90°C for 0.5 h. These studies suggest that the combination of PAMA and PVA for fabrication of MN arrays could have a great potential to develop both hydrogel and dissolving MN devices for transdermal drug delivery.

Electron beam curing of functionalized N-(4-hydroxy phenyl)maleimide monomers

Electron beam (E-beam) curing by different total radiation doses (100, 200, 300 and 400 kGy at 10 kGy per pass) of functionalized maleimides (20%) [ N-(4-acryloyloxy phenyl)maleimide, N-(4-methacryloyloxy phenyl)maleimide and N-(4-cyanato phenyl)maleimide] is carried out using N-vinyl-2-pyrrolidone as the reactive diluent (80%). The swelling studies indicate the presence of highly cross-linked structure in the polymer derived from cyanate-functionalized maleimide cured using 400 kGy electron beam (E-beam) irradiation. The thermal stabilities of all the polymers are studied using thermogravimetric analyzer. The materials cured using the highest radiation dose (400 kGy) are found to have better thermal stability compared to other materials cured using lower doses (100, 200 and 300 kGy at 10 kGy per pass). The degradation kinetic studies using the Vyazovkin method showed that the activation energies for the thermal degradation of polymeric materials got by E-beam irradiation of the monomers at 400 kGy are higher. Of all the materials investigated, liquid composition having N-(4-cyanato phenyl)maleimide (20%) and N-vinyl-2-pyrrolidone (80%) cured by E-beam radiation (400 kGy) showed better thermal stability.