Accelerating Reaction Rates of Biomolecules by Using Shear Stress in Artificial Capillary Systems.

Biomimetics is a design principle within chemistry, biology, and engineering, but chemistry biomimetic approaches have been generally limited to emulating nature's chemical toolkit while emulation of nature's physical toolkit has remained largely unexplored. To begin to explore this, we designed biophysically mimetic microfluidic reactors with characteristic length scales and shear stresses observed within capillaries. We modeled the effect of shear with molecular dynamics studies and showed that this induces specific normally buried residues to become solvent accessible. We then showed using kinetics experiments that rates of reaction of these specific residues in fact increase in a shear-dependent fashion. We applied our results in the creation of a new microfluidic approach for the multidimensional study of cysteine biomarkers. Finally, we used our approach to establish dissociation of the therapeutic antibody trastuzumab in a reducing environment. Our results have implications for the efficacy of existing therapeutic antibodies in blood plasma as well as suggesting in general that biophysically mimetic chemistry is exploited in biology and should be explored as a research area.

Protein Conjugation by Electrophilic Alkynylation Using 5-(Alkynyl)dibenzothiophenium Triflates.

5-(Alkynyl)dibenzothiophenium triflates are introduced as new reagents to prepare different protein conjugates through site-selective cysteine alkynylation. The protocol developed allows a highly efficient label of free cysteine-containing proteins with relevant biological roles, such as ubiquitin, the C2A domain of Synaptotagmin-I, or HER2 targeting nanobodies. An electrophilic bis-alkynylating reagent was also designed. The second alkynylating handle thus introduced in the desired protein enables access to protein-thiol, protein-peptide, and protein-protein conjugates, and even diubiquitin dimers can be prepared through this approach. The low excess of reagent needed, mild reaction conditions used, short reaction times, and stability of the S-C(alkyne) bonds at physiological conditions make this approach an interesting addition to the toolbox of classical, site-selective cysteine-conjugation methods.

Correction: Correction: Multi-scale microporous silica microcapsules from gas-in water-in oil emulsions.

Correction for 'Correction: Multi-scale microporous silica microcapsules from gas-in water-in oil emulsions' by Zenon Toprakcioglu et al., Soft Matter, 2020, 16, 3586-3586, DOI: .

A Microfluidic Co-Flow Route for Human Serum Albumin-Drug-Nanoparticle Assembly.

Nanoparticles are widely studied as carrier vehicles in biological systems because their size readily allows access through cellular membranes. Moreover, they have the potential to carry cargo molecules and as such, these factors make them especially attractive for intravenous drug delivery purposes. Interest in protein-based nanoparticles has recently gained attraction due to particle biocompatibility and lack of toxicity. However, the production of homogeneous protein nanoparticles with high encapsulation efficiencies, without the need for additional cross-linking or further engineering of the molecule, remains challenging. Herein, we present a microfluidic 3D co-flow device to generate human serum albumin/celastrol nanoparticles by co-flowing an aqueous protein solution with celastrol in ethanol. This microscale co-flow method resulted in the formation of nanoparticles with a homogeneous size distribution and an average size, which could be tuned from ≈100 nm to 1 µm by modulating the flow rates used. We show that the high stability of the particles stems from the covalent cross-linking of the naturally present cysteine residues within the particles formed during the assembly step. By choosing optimal flow rates during synthesis an encapsulation efficiency of 75±24 % was achieved. Finally, we show that this approach achieves significantly enhanced solubility of celastrol in the aqueous phase and, crucially, reduced cellular toxicity.

Multi-scale microporous silica microcapsules from gas-in water-in oil emulsions.

Controlling the surface area, pore size and pore volume of microcapsules is crucial for modulating their activity in applications including catalytic reactions, delivery strategies or even cell culture assays, yet remains challenging to achieve using conventional bulk techniques. Here we describe a microfluidics-based approach for the formation of monodisperse silica-coated micron-scale porous capsules of controllable sizes. Our method involves the generation of gas-in water-in oil emulsions, and the subsequent rapid precipitation of silica which forms around the encapsulated gas bubbles resulting in hollow silica capsules with tunable pore sizes. We demonstrate that by varying the gas phase pressure, we can control both the diameter of the bubbles formed and the number of internal bubbles enclosed within the silica microcapsule. Moreover, we further demonstrate, using optical and electron microscopy, that these silica capsules remain stable under particle drying. Such a systematic manner of producing silica-coated microbubbles and porous microparticles thus represents an attractive class of biocompatible material for biomedical and pharmaceutical related applications.

Correction: Multi-scale microporous silica microcapsules from gas-in water-in oil emulsions.

Correction for 'Multi-scale microporous silica microcapsules from gas-in water-in oil emulsions' by Zenon Toprakcioglu et al., Soft Matter, 2020, DOI: 10.1039/c9sm02274k.