Visible light was used as a tool to control hydrogel mechanical properties via defect formation, and subsequently dangling end defects generated with this approach were reacted for temporal stiffening.

Neutrophils are the primary responders to infection, rapidly migrating to sites of inflammation and clearing pathogens through a variety of antimicrobial functions. This response is controlled by a complex network of signals produced by vascular cells, tissue resident cells, other immune cells, and the pathogen itself. Despite significant efforts to understand how these signals are integrated into the neutrophil response, we still do not have a complete picture of the mechanisms regulating this process. This is in part due to the inherent disadvantages of the most-used experimental systems: in vitro systems lack the complexity of the tissue microenvironment and animal models do not accurately capture the human immune response. Advanced microfluidic devices incorporating relevant tissue architectures, cell-cell interactions, and live pathogen sources have been developed to overcome these challenges. In this review, we will discuss the in vitro models currently being used to study the neutrophil response to infection, specifically in the context of cell-cell interactions, and provide an overview of their findings. We will also provide recommendations for the future direction of the field and what important aspects of the infectious microenvironment are missing from the current models.

Click nucleic acids (CNAs) are a new, low-cost class of xeno nucleic acid (XNA) oligonucleotides synthesized by an efficient and scalable thiol-ene polymerization. In this work, a thorough characterization of oligo­(thymine) CNA–oligo­(adenine) DNA ((dA)20) hybridization was performed to guide the future implementation of CNAs in applications that rely on sequence-specific interactions. Microscale thermophoresis provided a convenient platform to rapidly and systematically investigate the effects of several factors (i.e., sequence, length, and salt concentration) on the CNA–DNA dissociation constant (K app). Because CNAs have limited water solubility, all studies were performed in aqueous-DMSO mixtures. CNA–DNA hybrids between oligo­(thymine) CNA (average length of 16 bases) and (dA)20 DNA have good stability despite the high organic content, a favorable attribute for many emerging applications of XNAs. In particular, the K app of CNA–DNA hybrids in 65 vol % DMSO with 10 mM sodium chloride (NaCl) was 0.74 ± 0.1 μM, whereas the K app for (dT)20–(dA)20 DNA–DNA was found to be 45 ± 2 μM in a buffer without DMSO but at the same NaCl concentration. CNA hybridized with DNA following Watson–Crick base pairing with excellent sequence specificity, discriminating even a single-base-pair mismatch, with K app values of 0.74 ± 0.1 and 3.7 ± 0.6 μM for complementary and single-base-pair mismatch sequences, respectively. As with dsDNA, increasing CNA length led to more stable hybrids as a result of increased base pairing, where K app decreased from 5.6 ± 0.8 to 0.27 ± 0.1 μM as the CNA average length increased from 7 to 21 bases. However, unlike DNA–DNA duplexes, which are largely unstable at low salt concentrations, the CNA–DNA stability does not depend on salt concentration, with K app remaining consistent between 1.0 and1.9 μM over a NaCl concentration range of 1.25–30 mM.