Design of sterile mucoadhesive hydrogels for use in drug delivery: Effect of radiation on network structure

Smart Hydrogel Bilayers Prepared by Irradiation

Environment-responsive hydrogel actuators have attracted tremendous attention due to their intriguing properties. Gamma radiation has been considered as a green cross-linking process for hydrogel synthesis, as toxic cross-linking agents and initiators were not required. In this work, chitosan/agar/P(N-isopropyl acrylamide-co-acrylamide) (CS/agar/P(NIPAM-co-AM)) and CS/agar/Montmorillonite (MMT)/PNIPAM temperature-sensitive hydrogel bilayers were synthesized via gamma radiation at room temperature. The mechanical properties and temperature sensitivity of hydrogels under different agar content and irradiation doses were explored. The enhancement of the mechanical properties of the composite hydrogel can be attributed to the presence of agar and MMT. Due to the different temperature sensitivities provided by the two layers of hydrogel, they can move autonomously and act as a flexible gripper as the temperature changes. Thanks to the antibacterial properties of the hydrogel, their storage time and service life may be improved. The as prepared hydrogel bilayers have potential applications in control devices, soft robots, artificial muscles and other fields.

Intravitreal hydrogels for sustained release of therapeutic proteins

This review highlights how hydrogel formulations can improve intravitreal protein delivery to the posterior segment of the eye in order to increase therapeutic outcome and patient compliance. Several therapeutic proteins have shown excellent clinical successes for the treatment of various intraocular diseases. However, drug delivery to the posterior segment of the eye faces significant challenges due to multiple physiological barriers preventing drugs from reaching the retina, among which intravitreal protein instability and rapid clearance from the site of injection. Hence, frequent injections are required to maintain therapeutic levels. Moreover, because the world population ages, the number of patients suffering from ocular diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR) is increasing and causing increased health care costs. Therefore, there is a growing need for suitable delivery systems able to tackle the current limitations in retinal protein delivery, which also may reduce costs. Hydrogels have shown to be promising delivery systems capable of sustaining release of therapeutic proteins and thus extending their local presence. Here, an extensive overview of preclinically developed intravitreal hydrogels is provided with attention to the rational design of clinically useful intravitreal systems. The currently used polymers, crosslinking mechanisms, in vitro/in vivo models and advancements are discussed together with the limitations and future perspective of these biomaterials.

Ultrasonic-assisted synthesis of sodium lignosulfonate-grafted poly(acrylic acid-co-poly(vinyl pyrrolidone)) hydrogel for drug delivery

Ultrasonic-assisted synthesis of sodium lignosulfonate-grafted hydrogel and the sustained release performance of the drug.

Exploiting a new glycerol-based copolymer as a route to wound healing: Synthesis, characterization and biocompatibility assessment

The use of biocompatible materials based on naturally derived monomers plays a key role in pharmaceutical and cosmetic industries. In this paper we describe the synthesis of a new low molecular weight copolymer, based on glycerol and l-tartaric acid, useful to develop biocompatible dermal patches with drug delivery properties. The copolymer's chemical composition was assessed by FT-IR (Fourier transform infrared spectroscopy), (1)H NMR ((1)H Nuclear Magnetic Resonance) and XPS (X-ray photoelectron spectroscopy), while its molecular weight distribution was estimated by SEC (size exclusion chromatography). Copolymer thermal properties were studied by TGA (thermogravimetric analysis). Biological evaluations by MTT assay and SEM (scanning electron microscopy) observations performed with murine fibroblasts and human keratinocytes (HaCaT) revealed a good compatibility of the proposed copolymer. Ciprofloxacin was selected as model drug and its release was evaluated by HPLC (high performance liquid chromatography), showing that the new copolymer supplied promising results as drug delivery system for wound healing applications. Furthermore, investigations on Skin-Mesenchymal stem cells (S-MSCs) behaviour and gene expression showed that the copolymer and its combination with ciprofloxacin did not affect their stemness. In this regard, the fabrication of dermal patches with new, low cost materials for local treatment of skin infections represents an attractive strategy in order to bypass the worrying side effects of systemic antibiotic therapy. Overall, the performed physico-chemical characterization, drug release test and biological evaluations showed that this new copolymer could be a promising tool for the in situ delivery of bioactive molecules during skin lesions treatment.

Hydrogel Antimicrobial Capture Coatings for Endotracheal Tubes: A Pharmaceutical Strategy Designed to Prevent Ventilator-Associated Pneumonia

This paper presents a novel strategy for the prevention of ventilator-associated pneumonia that involves coating poly(vinyl chloride, PVC) endotracheal tubes (ET) with hydrogels that may be subsequently used to entrap nebulized antimicrobial solutions. Candidate hydrogels were prepared containing a range of ratios of hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) from 100:0 to 70:30 using free radical polymerization and, when required, simultaneous attachment to PVC was performed. The mechanical properties, glass transition temperatures, swelling kinetics, uptake of gentamicin from an aqueous medium, and gentamicin release were characterized. Increasing the MAA content of the hydrogels significantly decreased the ultimate tensile strength, % elongation at break, Young's modulus, and increased the glass transition temperature, the swelling ratio, and gentamicin uptake. Microbial (Staphylococcus aureus and Pseudomonas aeruginosa) adherence to control (drug-free) hydrogels was observed; however, while adherence to gentamicin-containing p(HEMA) occurred, no adherence occurred to gentamicin-containing HEMA:MAA copolymers. Antimicrobial persistence of gentamicin-containing hydrogels was examined by determining the zone of inhibition against each microorganism on successive days. Hydrogel composition affected the observed antimicrobial persistence, with the hydrogel composed of 70:30 HEMA:MAA exhibiting >20 days persistence against S. aureus and P. aeruginosa, respectively. To simulate clinical use, the hydrogels (coated onto PVC) were first exposed to a nebulized solution of gentamicin (4 mL, 80 mg for 20 min), and then to nebulized bacteria (4 mL ca. 1×10(9) colony forming units mL(-1), 30 min). Viable bacteria were not observed on the gentamicin-treated p(HEMA: MAA) copolymers, whereas growth was observed on gentamicin-treated p(HEMA). In light of the excellent antimicrobial activity and physicochemical properties, p(HEMA: MAA) copolymers composed of ratios of 80:20 or 70:30 HEMA: MAA were identified as potentially useful coatings of endotracheal tubes to be used in conjunction with the clinical nebulization of gentamicin and designed for the prevention of ventilator-associated pneumonia.