Novel pH-sensitive IPNs of polyacrylamide-g-gum ghatti and sodium alginate for gastro-protective drug delivery

Biomedical applications of stimuli-responsive "smart" interpenetrating polymer network hydrogels

In recent years, owing to the ongoing advancements in polymer materials, hydrogels have found increasing applications in the biomedical domain, notably in the realm of stimuli-responsive "smart" hydrogels. Nonetheless, conventional single-network stimuli-responsive "smart" hydrogels frequently exhibit deficiencies, including low mechanical strength, limited biocompatibility, and extended response times. In response, researchers have addressed these challenges by introducing a second network to create stimuli-responsive "smart" Interpenetrating Polymer Network (IPN) hydrogels. The mechanical strength of the material can be significantly improved due to the topological entanglement and physical interactions within the interpenetrating structure. Simultaneously, combining different network structures enhances the biocompatibility and stimulus responsiveness of the gel, endowing it with unique properties such as cell adhesion, conductivity, hemostasis/antioxidation, and color-changing capabilities. This article primarily aims to elucidate the stimulus-inducing factors in stimuli-responsive "smart" IPN hydrogels, the impact of the gels on cell behaviors and their biomedical application range. Additionally, we also offer an in-depth exposition of their categorization, mechanisms, performance characteristics, and related aspects. This review furnishes a comprehensive assessment and outlook for the advancement of stimuli-responsive "smart" IPN hydrogels within the biomedical arena. We believe that, as the biomedical field increasingly demands novel materials featuring improved mechanical properties, robust biocompatibility, and heightened stimulus responsiveness, stimuli-responsive "smart" IPN hydrogels will hold substantial promise for wide-ranging applications in this domain.

Design of polyacrylamide grafted sesbania gum-mediated pH-responsive IPN-based microbeads for delivery of diclofenac sodium: In-vitro-in-vivo characterizations

Microwave-assisted grafting of polyacrylamide on sesbania gum (PAAM-g-SG) was implemented employing a 3² full factorial experimental design and was hydrolyzed using sodium hydroxide (NaOH) to form H-PAAM-g-SG. Further, the diclofenac sodium-loaded novel pH-sensitive interpenetrating polymeric network (IPN) microbeads were designed using an optimized H-PAAM-g-SG and sodium alginate (SA). Different spectroscopic analysis including FTIR spectroscopy, ¹H NMR spectroscopy, elemental analysis, thermal analysis, etc. was performed to confirm the synthesis of PAAM-g-SG and diclofenac-loaded pH-sensitive IPN H-PAAM-g-SG-SA microbeads. Here, Ca⁺² ions combine with two strands of SA and form a round-shape structure that encloses uncross-linked H-PAAM-g-SG polymer and diclofenac sodium. As well, glutaraldehyde (GL) addition improved the mechanical strength due to acetal structure between hydroxyl of H-PAAM-g-SG and aldehyde of GL. The drug entrapment was confirmed proportional relationship to the Ca⁺² ions concentration whereas an increase in GL concentration resulted in a reduced drug entrapment. The pH pulsatile study assured the reversible swelling-shrinkage behavior of IPN microbeads due to the carboxyl group of PAAM-g-SG. The drug release from H-PAAM-g-SG-SA microbeads (batch: S9) was found to be 84.21 % (12h) which was non-significant (p > 0.05; f2 = 79 ∼ 90) over marketed formulation (83.31 %). Moreover, it follows the Korsmeyer Peppas (R² = 0.996) as the best-fit release kinetic model. The pH-sensitive release of diclofenac sodium from IPN H-PAAM-g-SG-SA microbeads was assured based on in vivo anti-inflammatory activity (p < 0.05). Therefore, developed novel pH-sensitive IPN microbeads based on H-PAAM-g-SG are a promising polymeric carrier substitute for delivery of drugs actuated by a pH stimulus.

A comprehensive review on the COVID-19 vaccine and drug delivery applications of interpenetrating polymer networks

An interpenetrating polymer network (IPNs) is a concoction of two or more polymers (natural, synthetic, and/or a combination of both) in which at least one polymer is synthesized or crosslinked in the intimate presence of the other. These three-dimensional networked systems have gained prominence in a series of biomedical applications, especially in the last two decades. The last decades witnessed a surge in the meaningful applications of interpenetrating polymer networks, especially in drug delivery as simple IPN systems advanced and resulted in the formation of highly efficient microspheres, nanoparticles, nanogels, and hydrogels, intelligent enough to sense and respond to changes in external stimuli such as temperature, pH, and ionic strength. The structure of the polymers, crosslinking agents, crosslinking density, and polymerization method play an integral role in determining the properties and application of IPNs in drug delivery. This review article is a modest effort to highlight the importance and applications of different types of interpenetrating polymer networks for the sustained, site-specific drug delivery of various therapeutic formulations, as witnessed in scientific research literature over the past 22 years (2000-2022). A special section of the manuscript is devoted to studying the efficacy of network polymers in vaccine delivery and highlighting the future scope (if any) of incorporating the IPN system in COVID-related vaccine/drug delivery. Four key focus areas in this review article [1, 2].

A sodium alginate-based sustained-release IPN hydrogel and its applications

Interpenetrating polymer network (IPN) hydrogels are crosslinked by two or more polymer networks, providing free volume space in the three-dimensional network structure, and providing conditions for the sustained and controlled release of drugs. The IPN hydrogels based on the natural polymer sodium alginate can form a stable porous network structure. Due to its excellent biocompatibility, the loaded drug can be sustained to the maximum extent without affecting its pharmacological effect. Sodium alginate-based IPN hydrogels have broad application prospects in the field of sustained and controlled drug release. This paper begins with an overview of the formation of alginate-based IPN hydrogels; summarizes the types of alginate-based IPN hydrogels; and discusses the pharmaceutical applications of alginate-based IPN hydrogels. We aim to give an overview of the research on IPN hydrogels based on sodium alginate in sustained and controlled drug release systems.

Core-shell alginate-ghatti gum modified montmorillonite composite matrices for stomach-specific flurbiprofen delivery

Novel alginate-arabic gum (AG) gel membrane coated alginate-ghatti gum (GG) modified montmorillonite (MMT) composite matrices were developed for intragastric flurbiprofen (FLU) delivery by combining floating and mucoadhesion mechanisms. The clay-biopolymer composite matrices containing FLU as core were accomplished by ionic-gelation technique. Effects of polymer-blend (alginate:GG) ratios and crosslinker (CaCl₂) concentrations on drug entrapment efficiency (DEE, %) and cumulative drug release after 8h (Q_8h, %) were studied to optimize the core matrices by a 3² factorial design. The optimized matrices (F-O) demonstrated DEE of 91.69±1.43% and Q_8h of 74.96±1.56% with minimum errors in prediction. The alginate-AG gel membrane enveloped optimized matrices (F-O, coated) exhibited superior buoyancy, better ex vivo mucoadhesion and slower drug release rate. The drug release profile of FLU-loaded uncoated and coated optimized matrices was best fitted in Korsmeyer-Peppas model with anomalous diffusion and case-II transport driven mechanism, respectively. The uncoated and coated matrices containing FLU were also characterized for drug-excipients compatibility, drug crystallinity, thermal behaviour and surface morphology. Thus, the newly developed alginate-AG gel membrane coated alginate-GG modified MMT composite matrices are appropriate for intragastric delivery of FLU over an extended period of time with improved therapeutic benefits.

Peptide dendrimer-conjugates of ketoprofen: Synthesis and ex vivo and in vivo evaluations of passive diffusion, sonophoresis and iontophoresis for skin delivery

The aim of this study was to evaluate skin delivery of ketoprofen when covalently tethered to mildly cationic (2⁺ or 4⁺) peptide dendrimers prepared wholly by solid phase peptide synthesis. The amino acids glycine, arginine and lysine formed the dendrimer with ketoprofen tethered either to the lysine side-arm (N_ε) or periphery of dendrimeric branches. Passive diffusion, sonophoresis- and iontophoresis-assisted permeation of each peptide dendrimer-drug conjugate (D1-D4) was studied across mouse skin, both in vitro and in vivo. In addition, skin toxicity of dendrimeric conjugates when trialed with iontophoresis or sonophoresis was also evaluated. All dendrimeric conjugates improved aqueous solubility at least 5-fold, compared to ketoprofen alone, while also exhibiting appreciable lipophilicity. In vitro passive diffusion studies revealed that ketoprofen in its native form was delivered to a greater extent, compared with a dendrimer-conjugated form at the end of 24h (Q_24h (μg/cm²): ketoprofen (68.06±3.62)>D2 (49.62±2.92)>D4 (19.20±0.89)>D1 (6.45±0.40)>D3 (2.21±0.19). However, sonophoresis substantially increased the skin permeation of ketoprofen-dendrimer conjugates in 30min (Q_30min (μg/cm²): D4 (122.19±7.14)>D2 (66.74±3.86)>D1 (52.10±3.22)>D3 (41.66±3.22)) although ketoprofen alone again proved superior (Q_30min: 167.99±9.11μg/cm²). Next, application of iontophoresis was trialed and shown to considerably increase permeation of dendrimeric ketoprofen in 6h (Q_6h (μg/cm²): D2 (711.49±39.14)>D4 (341.23±16.43)>D3 (89.50±4.99)>D1 (50.91±2.98), with a Q_6h value of 96.60±5.12μg/cm² for ketoprofen alone). In vivo studies indicated that therapeutically relevant concentrations of ketoprofen could be delivered transdermally when iontophoresis was paired with D2 (985.49±43.25ng/mL). Further, histopathological analysis showed that the dendrimeric approach was a safe mode as ketoprofen alone. The present study successfully demonstrates that peptide dendrimer conjugates of ketoprofen, when combined with non-invasive modalities, such as iontophoresis can enhance skin permeation with clinically relevant concentrations achieved transdermally.

In vitro and in vivo assessment of novel pH-sensitive interpenetrating polymer networks of a graft copolymer for gastro-protective delivery of ketoprofen

Novel pH-sensitive IPN microbeads exhibited drug release in response to changing pH and reduced side effects of ketoprofenin vivo.