Development of biomaterial composite hydrogel as a passive sampler with potential application in wastewater-based surveillance.

Nowadays, the need to track fast-spreading infectious diseases has raised due to the recent COVID-19 disease pandemic. As a response, Wastewater-based Surveillance (WBS) has emerged as an early detection and disease tracking method for large populations that enables a comprehensive overview of public health allowing for a faster response from public health sector to prevent large outbreaks. The process to achieve WBS requires a highly intensive sampling strategy with either expensive equipment or trained personnel to continuously sample. The sampling problem can be addressed by passive sampler development. Chitosan-based hydrogels are recognized for their capability to sample and remove various contaminants from wastewater, including metals, dyes, pharmaceuticals, among others. However, chitosan-based hydrogels unique characteristics, can be exploited to develop passive samplers of genetic material that can be a very valuable tool for WBS. This study aimed to develop a novel chitosan hydrogel formulation with enhanced characteristics suitable for use as a passive sampler of genetic material and its application to detect disease-causing pathogens present in wastewater. The study evaluates the effect of the concentration of different components on the formulation of a Chitosan composite hydrogel (Chitosan, Glutaraldehyde, Microcrystalline cellulose (MCC), and Polyethylene glycol (PEG)) on the hydrogel properties using a Box Hunter & Hunter experimental matrix. Hydrogels' weight, thickness, swelling ratio, microscopic morphology (SEM), FTIR assay, and zeta potential were characterized. The resulting hydrogel formulations were shown to be highly porous, positively charged (Zeta potential up to 35.80 ± 1.44 mV at pH 3) and with high water swelling capacity (up to 703.89 ± 15.00 %). Based on the results, a formulation from experimental design was selected and then evaluated its capacity to adsorb genetic material from a control spiked water with Influenza A virus synthetic vector. The adsorption capacity of the selected formulation was 4157.04 ± 64.74 Gene Copies/mL of Influenza A virus synthetic vector. The developed hydrogel showed potential to be used as passive sampler for pathogen detection in wastewater. However, deeper research can be conducted to improve adsorption, desorption and extraction techniques of genetic material from chitosan-hydrogel matrices.

Hydrogel Based on Chitosan/Gelatin/Poly(Vinyl Alcohol) for In Vitro Human Auricular Chondrocyte Culture.

Three-dimensional (3D) hydrogels provide tissue-like complexities and allow for the spatial orientation of cells, leading to more realistic cellular responses in pathophysiological environments. There is a growing interest in developing multifunctional hydrogels using ternary mixtures for biomedical applications. This study examined the biocompatibility and suitability of human auricular chondrocytes from microtia cultured onto steam-sterilized 3D Chitosan/Gelatin/Poly(Vinyl Alcohol) (CS/Gel/PVA) hydrogels as scaffolds for tissue engineering applications. Hydrogels were prepared in a polymer ratio (1:1:1) through freezing/thawing and freeze-drying and were sterilized by autoclaving. The macrostructure of the resulting hydrogels was investigated by scanning electron microscopy (SEM), showing a heterogeneous macroporous structure with a pore size between 50 and 500 µm. Fourier-transform infrared (FTIR) spectra showed that the three polymers interacted through hydrogen bonding between the amino and hydroxyl moieties. The profile of amino acids present in the gelatin and the hydrogel was determined by ultra-performance liquid chromatography (UPLC), suggesting that the majority of amino acids interacted during the formation of the hydrogel. The cytocompatibility, viability, cell growth and formation of extracellular matrix (ECM) proteins were evaluated to demonstrate the suitability and functionality of the 3D hydrogels for the culture of auricular chondrocytes. The cytocompatibility of the 3D hydrogels was confirmed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, reaching 100% viability after 72 h. Chondrocyte viability showed a high affinity of chondrocytes for the hydrogel after 14 days, using the Live/Dead assay. The chondrocyte attachment onto the 3D hydrogels and the formation of an ECM were observed using SEM. Immunofluorescence confirmed the expression of elastin, aggrecan and type II collagen, three of the main components found in an elastic cartilage extracellular matrix. These results demonstrate the suitability and functionality of a CS/Gel/PVA hydrogel as a 3D support for the auricular chondrocytes culture, suggesting that these hydrogels are a potential biomaterial for cartilage tissue engineering applications, aimed at the regeneration of elastic cartilage.

Gelation Kinetics of Hydrogels Based on Acrylamide⁻AMPS⁻NVP Terpolymer, Bentonite, and Polyethylenimine for Conformance Control of Oil Reservoirs.

Relatively smaller volumes of gelling systems had been used to address conformance problems located near the wellbore in oil reservoirs with harsh temperature and salinity conditions. These gelling systems were formulated with high concentrations of low-molecular-weight acrylamide-based polymers crosslinked with polyethylenimine (PEI). However, for in-depth conformance control, in which large gelant volumes and long gelation times were required, lower-base polymer loadings were necessary to ensure the economic feasibility of the treatment. In this study, a gelling system with high-molecular weight 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N-vinyl-2-pyrrolidone (NVP), acrylamide terpolymer, and PEI, with the addition of bentonite as a filler, was formulated. The influence of the gelant formulation and reservoir conditions on the gelation kinetics and final gel strength of the system was investigated through bottle tests and rheological tests. The addition of clay in the formulation increased the gelation time, thermal stability, and syneresis resistance, and slightly improved the final gel strength. Furthermore, samples prepared with polymer and PEI concentrations below 1 wt %, natural bentonite, and PEI with molecular weight of 70,000 kg/kmol and pH of 11: (i) presented good injectivity and propagation parameters (pseudoplastic behavior and viscosity ~25 mPa·s); (ii) showed suitable gelation times for near wellbore (~5 h) or far wellbore (~21 h) treatments; and (iii) formed strong composite hydrogels (equilibrium complex modulus ~10⁻20 Pa and Sydansk code G to H) with low syneresis and good long-term stability (~3 to 6 months) under harsh conditions. Therefore, the use of high-molecular-weight base polymer and low-cost clay as active filler seems promising to improve the cost-effectiveness of gelling systems for in-depth conformance treatments under harsh conditions of temperature and salinity/hardness.

Poly(vinyl alcohol)/cellulose nanowhiskers nanocomposite hydrogels for potential wound dressings.

Polyvinyl alcohol (PVA)/cellulose nanowhisker (CNW) nanocomposite hydrogels to be used for wound dressing were obtained by freezing-thawing technique and characterized by means of morphological, physical, thermal, mechanical, barrier and antimicrobial properties. First, cellulose nanowhiskers were obtained by the acid hydrolysis of commercial crystalline microcellulose (MCC) and characterized by its size, shape, morphological, structural and thermal properties. Then, PVA/CNW nanocomposites with several CNW contents (0, 1, 3, 5 and 7wt.%) were obtained. Morphological, thermal, chemical and physical characterization of the PVA/CNW nanocomposite hydrogels was carried out. It was found that the addition of CNW to the hydrogel allows controlling the pore morphology of the samples. On the other hand, the transparency of the samples was maintained, the thermal stability was increased, the mechanical properties were improved and the water vapor transmission rate was in the range of wound dressing applications after CNW incorporation inside the PVA hydrogel matrix. The evaluation of microbial penetration showed that the prepared hydrogels can be considered as a good barrier against different microorganisms. All obtained results indicate that the PVA/CNW materials are promising to be used as wound dressing.