Open Access

Photocrosslinkable formulations based on the radical thiol-ene reaction are considered better alternatives than methacrylated counterparts for light-based fabrication processes. This study quantifies differences between thiol-ene and methacrylated crosslinked hydrogels in terms of precursors stability, the control of the crosslinking process, and the resolution of printed features particularized for hyaluronic acid (HA) inks at concentrations relevant for bioprinting. First, the synthesis of HA functionalized with norbornene, allyl ether, or methacrylate groups with the same molecular weight and comparable degrees of functionalization is presented. The thiol-ene hydrogel precursors show storage stability over 15 months, 3.8 times higher than the methacrylated derivative. Photorheology experiments demonstrate up to 4.7-times faster photocrosslinking. Network formation in photoinitiated thiol-ene HA crosslinking allows higher temporal control than in methacrylated HA, which shows long post-illumination hardening. Using digital light processing, 4% w/v HA hydrogels crosslinked with a dithiol allowed printing of 13.5 × 4 × 1 mm3 layers with holes of 100 µm resolution within 2 s. This is the smallest feature size demonstrated in DLP printing with HA-based thiol-ene hydrogels. The results are important to estimate the extent to which the synthetic effort of introducing –ene functions can pay off in the printing step.

As ubiquitous defense mechanisms in Nature, stinger-like structures cover a size range over six orders of magnitude. While their composition varies, we uncovered a common geometric trait: a non-linear relationship between diameter and distance from the tip, following a power law with an exponent universally between 2 and 3. Through a combination of theoretical mechanics and experiments, we interpret this universal shape to be the result of a competition between penetration and buckling, motivated by the limitations of the mechanical properties of the stinger material. Our study not only resolves a mystery underlying the structural optimization of convergently evolved natural stingers, but also can offer inspiration for efficient needles in technology or biomedicine, made from sustainable non-metallic materials.

Antibiotic resistance in chronic lung infections caused by Pseudomonas aeruginosa requires alternative approaches to improve antibiotic efficacy. One promising approach is the use of adjuvant compounds that complement antibiotic therapy. This study explores the potential of menadione as an adjuvant to azithromycin against planktonic cells and biofilms of P. aeruginosa, focusing on its mechanisms of action and cytotoxicity in pulmonary cell models. Methods: The effect of menadione in improving the antibacterial and antibiofilm potency of azithromycin was tested against P. aeruginosa. Mechanistic studies in P. aeruginosa and AZMr-E. coli DH5α were performed to probe reactive oxygen species (ROS) production and bacterial membrane disruption. Cytotoxicity of antibacterial concentrations of menadione was assessed by measuring ROS levels and membrane integrity in Calu-3 and A549 lung epithelial cells. Results: Adding 0.5 µg/mL menadione to azithromycin reduced the minimum inhibitory concentration (MIC) by four-fold and the minimum biofilm eradication concentration (MBEC) by two-fold against P. aeruginosa. Adjuvant mechanisms of menadione involved ROS production and disruption of bacterial membranes. Cytotoxicity tests revealed that antibacterial concentrations of menadione (≤64 µg/mL) did not affect ROS levels or membrane integrity in lung cell lines. Conclusions: Menadione enhanced the efficacy of azithromycin against P. aeruginosa while exhibiting a favorable safety profile in lung epithelial cells at antibacterial concentrations. These findings suggest that menadione is a promising antibiotic adjuvant. However, as relevant data on the toxicity of menadione is sparse, further toxicity studies are required to ensure its safe use in complementing antibiotic therapy.

The functional integration of biological switches with synthetic building blocks enables the design of modular, stimulus-responsive biohybrid materials. By connecting the individual modules via diffusible signals, information-processing circuits can be designed. Such systems are, however, mostly limited to respond to either small molecules, proteins, or optical input thus limiting the sensing and application scope of the material circuits. Here, a highly modular biohybrid material is design based on CRISPR/Cas13a to translate arbitrary single-stranded RNAs into a biomolecular material response. This system exemplified by the development of a cascade of communicating materials that can detect the tumor biomarker microRNA miR19b in patient samples or sequences specific for SARS-CoV. Specificity of the system is further demonstrated by discriminating between input miRNA sequences with single-nucleotide differences. To quantitatively understand information processing in the materials cascade, a mathematical model is developed. The model is used to guide systems design for enhancing signal amplification functionality of the overall materials system. The newly designed modular materials can be used to interface desired RNA input with stimulus-responsive and information-processing materials for building point-of-care suitable sensors as well as multi-input diagnostic systems with integrated data processing and interpretation.

Engineered living materials (ELMs), which usually comprise bacteria, fungi, or animal cells entrapped in polymeric matrices, offer limitless possibilities in fields like drug delivery or biosensing. Determining the conditions that sustain ELM performance while ensuring compatibility with ELM hosts is essential before testing them in vivo. This is critical to reduce animal experimentation and can be achieved through in vitro investigations. Currently, there are no standards that ensure ELM compatibility with host tissues. Towards this goal, we designed a 96-well plate-based screening method to streamline ELM growth across culture conditions and determine their compatibility potential in vitro. We showed proliferation of three bacterial species encapsulated in hydrogels over time and screened six different cell culture media. We fabricated ELMs in bilayer and monolayer formats and tracked bacterial leakage as a measure of ELM biocontainment. After screening, an appropriate medium was selected that sustained growth of an ELM, and it was used to study cytocompatibility in vitro. ELM cytotoxicity on murine fibroblasts and human monocytes was studied by adding ELM supernatants and measuring cell membrane integrity and live/dead staining, respectively, proving ELM cytocompatibility. Our work illustrates a simple setup to streamline the screening of compatible environmental conditions of ELMs with the host.