Native Spider Silk-Based Antimicrobial Hydrogels for Biomedical Applications

Novel antimicrobial natural polymeric hybrid hydrogels based on hyaluronic acid (HA) and spider silk (Ss) were prepared using the chemical crosslinking method. The effects of the component ratios on the hydrogel characteristics were observed parallel to the primary physicochemical characterization of the hydrogels with scanning electron microscopic imaging, Fourier-transform infrared spectroscopy, and contact angle measurements, which confirmed the successful crosslinking, regular porous structure, exact composition, and hydrophilic properties of hyaluronic acid/spider silk-based hydrogels. Further characterizations of the hydrogels were performed with the swelling degree, enzymatic degradability, viscosity, conductivity, and shrinking ability tests. The hyaluronic acid/spider silk-based hydrogels do not show drastic cytotoxicity over human postnatal fibroblasts (HPF). Hydrogels show extraordinary antimicrobial ability on both gram-negative and gram-positive bacteria. These hydrogels could be an excellent alternative that aids in overcoming antimicrobial drug resistance, which is considered to be one of the major global problems in the biomedical industry. Hyaluronic acid/spider silk-based hydrogels are a promising material for collaborated antimicrobial and anti-inflammatory drug delivery systems for external use. The rheological properties of the hydrogels show shear-thinning properties, which suggest that the hydrogels could be applied in 3D printing, such as in the 3D printing of antimicrobial surgical meshes.

pH-Stat Titration: A Rapid Assay for Enzymatic Degradability of Bio-Based Polymers

Bio-based polymers have been suggested as one possible opportunity to counteract the progressive accumulation of microplastics in the environments. The gradual substitution of conventional plastics by bio-based polymers bears a variety of novel materials. The application of bioplastics is determined by their stability and bio-degradability, respectively. With the increasing implementation of bio-based plastics, there is also a demand for rapid and non-elaborate methods to determine their bio-degradability. Here, we propose an improved pH Stat titration assay optimized for bio-based polymers under environmental conditions and controlled temperature. Exemplarily, suspensions of poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) microparticles were incubated with proteolytic and lipolytic enzymes. The rate of hydrolysis, as determined by counter-titration with a diluted base (NaOH), was recorded for two hours. PLA was hydrolyzed by proteolytic enzymes but not by lipase. PBS, in contrast, showed higher hydrolysis rates with lipase than with proteases. The thermal profile of PLA hydrolysis by protease showed an exponential increase from 4 to 30 °C with a temperature quotient Q10 of 5.6. The activation energy was 110 kJ·mol−1. pH-Stat titration proved to be a rapid, sensitive, and reliable procedure supplementing established methods of determining the bio-degradability of polymers under environmental conditions.

In silico design and validation of a highly degenerate primer pair: a systematic approach

Background The techniques of amplifying genetic materials have enabled the extensive study of several biological activities outside the biological milieu of living systems. More recently, this approach has been extended to amplify population of genes, from evolutionarily related gene family for detection and evaluation of microbial consortial with several unique potentialities (e.g., enzymatic degradability). Conceivably, primer mixtures containing substitutions of different bases at specific sites (degenerate primers) have enabled the amplification of these genes in PCR reaction. However, the degenerate primer design problem (DPD) is a constraint to designing this kind of primer. To date, different algorithms now exist to solve various versions of DPD problem, many of which, only few addresses and satisfy the criteria to design primers that can extensively cover high through-put sequences while striking the balance between specificity and efficiency. The highly degenerate primer (HYDEN) design software program primarily addresses this variant of DPD problem termed “maximum coverage-degenerate primer design (MC-DPD)” and its heuristics have been substantiated for optimal efficiency from significant successes in PCR. In spite of the premium presented for designing degenerate primers, literature search has indicated relatively little use of its heuristics. This has been thought to result from the complexity of the program since it is run only by command-line, hence limiting its accessibility. To solve this problem, researchers have optionally considered the manual design of degenerate primers or design through software programs that provides accessibility through a graphical user interface (GUI). Realizing this, we have attempted in this study to provide a user-friendly approach for researchers with little or no background in bioinformatics to design degenerate primers using HYDEN Results Virtual Tests of our designed degenerate primer pair through in silico PCR substantiated the correspondence between efficiency and coverage with the target sequences as pre-defined by the initial HYDEN output, thereby validating the potentials of HYDEN to effectively solve the MC-DPD problem. Additionally, the designed primer-pair mechanistically amplified all sequences used as a positive control with no amplification observed in the negative controls. Conclusion In this study, we provided a turnkey protocol to simplify the design of degenerate primers using the heuristics of the HYDEN software program.

Photo-Crosslinkable Double-Network Hyaluronic Acid Based Hydrogel Dressing

Hyaluronic acid (HA)-based hydrogels are widely used in biomedical applications due to their excellent biocompatibility and enzymatic degradability. In this paper a photo-crosslinking double-network hyaluronic acid-based hydrogel dressing was proposed. Hyaluronic acid can be UV-crosslinked by modification with methacrylic anhydride (HA-MA) and disulfide-crosslinked by modification with 3,3'-dithiobis (propionylhydrazide) (DTP) (HA-SH). The mixings of these two materials at different ratios were produced. All the samples can be quickly gelled at 365 nm for 10 s. The rheological tests show that the storage modulus (G') of the double network (HA-SH/HA-MA) hydrogel is increased with the increase of HA-SH content. The HA-SH/HA-MA hydrogel has porous structure, high swelling ratio and Controlled degradation rate. In vitro degradation tests show that the ratio of HA-SH/HA-MA ratio was 9:1 (S9M1) in 100 U/ml hyaluronidase (Hase) degraded by 89.91±2.26% at 11d. The cytocompatibility of HA-SH/HA-MA hydrogels was proved by Live/Dead stainings and CCK-8 assays in the human dermis fibroblasts (HDF) cells test. All these results highlight the biological potential of the HA-SH/HA-MA hydrogels for DFU intervention.

Inulin: A promising carrier for controlled and targeted drug delivery system

The delivery of a drug to the preferred site of action is referred to as drug targeting. The benefits of drug targeting are a reproducible and controlled release rate of the therapeutic compound, which forestalls overdose. Due to the potential to treat colonic diseases with minimum side effects, colon targeting has become of high interest over the last decades. Inulin was investigated for its potential as encapsulation material regarding its enzymatic degradability and its drug release behaviour. Inulin is a polysaccharide with a widespread range of therapeutic uses such as a carrier in a drug delivery vehicle, as a diagnostic/analytical tool or as a dietary fibre with additional health benefits. In the main, much research has focused on inulin as a drug delivery carrier for colon-specific drug delivery. The justification for this is its potential to survive in the stomach’s acidic environment. This unique stability and strength are utilized in many ways to deliver drugs safely to the colon, where they can be easily absorbed through the gut epithelium into the blood. There are also some proofs that inulin’s prebiotic features also lead to health benefits, mainly for patients with inflammatory bowel disease or in the prevention of colonic cancer. Inulin based hydrodynamic research will be useful to discover the potential of inulin.

Study on the Thermal Properties and Enzymatic Degradability of Chiral Polyamide-Imides Films Based on Amino Acids

Six kinds of chiral polyamide-imides (PAI3a–3f) have successfully been synthesized via direct polycondensation. The thermal properties of the materials were evaluated by the gravimetric analysis (TGA) and differential scanning calorimetry (DSC). A thermal test was conducted and showed that the polymers have good thermal stability. The Tg values were affected by the volume effect of the side groups, the internal plasticizing effect and the isolation effect. Polyamide-imides (PAIs) with L configuration showed higher Tg values than PAIs with D configuration. In the enzymatic degradation experiments of PAI films, the results showed that the structure of amino acids have the greatest influence on the degradation performance of PAIs relative to chirality. The PAI films with simple side groups and L configurations were easier to degrade. The degradation rate of natural chiral PAIs were higher than those of non-natural chiral PAIs. This makes it possible to develop polymer materials with specific degradation rates.