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Developing an engineerable chemical reaction that is triggerable for simultaneous chemical bond formation and cleavage by external cues offers tunability and orthogonality which is highly desired in many biological and materials applications. Here, we present a chemical switch that concurrently captures these features in response to chemically and biologically abundant and important cues, viz., thiols and amines. This thiol/amine-triggerable chemical switch is based on a Triggerable Michael Acceptor (TMAc) which bears good leaving groups at its β-position. The acceptor undergoes a “trigger-to-release” process where thiol/amine addition triggers cascaded release of leaving groups and generates a less activated acceptor. The newly generated TMAc can be further reversed to liberate the original thiol/amine by a second nucleophile trigger through a “trigger-to-reverse” process. Within the small molecular volume of the switch, we have shown five locations that can be engineered to achieve tunable “trigger-to-release” kinetics and tailored reversibility. The potential of the engineerable bonding/debonding capability of the chemical switch is demonstrated by applications in cysteine-selective and reversible protein modification, universal self-immolative linkers, and orthogonally addressable hydrogels., A triggerable Michael acceptor (TMAc) with programmable reactivity and reversibility for simultaneous coupling and decoupling has been developed for selective protein modification, self-immolative linker and orthogonally addressable hydrogel.

Correction for ‘Encapsulating bacteria in alginate-based electrospun nanofibers’ by Emily Diep et al., Biomater. Sci., 2021, 9, 4364–4373, DOI: 10.1039/D0BM02205E.

Microfluidic strategies to enable the growth and subsequent serial crystallographic analysis of micro-crystals have the potential to facilitate both structural characterization and dynamic structural studies of protein targets that have been resistant to single-crystal strategies. However, adapting microfluidic crystallization platforms for micro-crystallography requires a dramatic decrease in the overall device thickness. We report a robust strategy for the straightforward incorporation of single-layer graphene into ultra-thin microfluidic devices. This architecture allows for a total material thickness of only ~1 μm, facilitating on-chip X-ray diffraction analysis while creating a sample environment that is stable against significant water loss over several weeks. We demonstrate excellent signal-to-noise in our X-ray diffraction measurements using a 1.5 μs polychromatic X-ray exposure, and validate our approach via on-chip structure determination using hen egg white lysozyme (HEWL) as a model system. Although this work is focused on the use of graphene for protein crystallography, we anticipate that this technology should find utility in a wide range of both X-ray and other lab on a chip applications.

Nanofiber mats hold potential in numerous applications that interface with microorganisms. However, a fundamental study that quantifies the transport of microorganisms into three-dimensional microenvironments, such as nanofiber mats, has not yet been conducted. Here, we evaluate the microbial uptake capacity of three hydrophilic cellulose sorbents, a high surface area electrospun nanofiber mat, as well as two commercial products, a macrofibrous Fisherbrand fabric and an adsorptive Sartorius membrane. The small average fiber diameter (∼1.0 μm) and large porosity of the nanofiber mats enabled a 21 times greater collection of Escherichia coli K12 per milligram of material than the macrofibrous Fisherbrand controls and 220 times more than the Sartorius controls. In most cases, the exposure time of the nanofiber mats to the microorganisms was sufficient to reach a quasi-equilibrium state of microbial uptake, allowing the calculation of an adsorption coefficient (Keq) that relates the concentration of cells in the sorbent to the concentration of cells remaining in solution. The Keq of the nanofiber mats was 420, compared to 9.2 and 0.67 for the Fisherbrand and Sartorius controls, respectively. In addition to E. coli, we studied the cellulose nanofiber mat uptake of two additional medically relevant and distinct microorganisms, Gram-negative Pseudomonas aeruginosa PA01 and Gram-positive Staphylococcus aureus MW2, to probe whether microorganism removal is bacteria-specific. The high uptake capacity of all three bacteria by the nanofiber mats indicates that microbial uptake is independent of the microorganism's adhesion mechanism. This work suggests that cellulose nanofiber mat “sponges” are a green platform technology that has the potential to remove detrimental microorganisms from wounds, trap bacteria within a protective military textile, or remediate contaminated water.