Chem & Bio Engineering最新文献

The rapid and reversible adhesion between solids is of great significance, particularly in fields such as biomedicine, intelligent machines, and bioelectronic sensors. Hydrogels, as soft materials, play a vital role in reversible adhesion. To achieve a wider range of applications, it is essential to enhance the intelligence of hydrogels. However, the preparation of reversible adhesive hydrogels with remote control, reversible adhesion, rapid response, and no residue remains a challenge in the field. Herein, we developed a light-controlled reversible adhesive hydrogel by integrating temperature-controlled reversible adhesion with the photothermal response capabilities of Fe₃O₄. The hydrogel can adhere/desorb reversibly under temperature control and allows for remote adhesion control using infrared light. Under infrared light irradiation, surface water causes carboxylic acid groups to migrate to the surface, thereby shielding the catechol groups. This results in insufficient adhesive groups at the interface to form interactions with opposing surfaces. Without infrared light irradiation, the adhesive functional groups are exposed, allowing interaction forces to form between the surface with the adhesion groups and the opposing surfaces. This smart hydrogel holds significant potential for future applications in wound dressings, wearable devices, and soft robots.

Microlenses are the basis of diverse modern instruments, which demand for more flexible fabrication. Thermal reflowing after photolithography of non-cross-linked polymers is the most widely applied strategy for manufacturing final products or primary molds of microlenses with desired microcurvatures. However, this approach can commonly form only one specific curvature for the same precursor system, lacking manufacturing flexibility. Here we report the direct growth of microstructures with flexible control of the curvature after one-step photolithography. This method relies on spatial UV irradiation, which induces network rearrangements in a dynamically cross-linked hydrogel. Upon subsequent water swelling, the irradiated locations develop microstructures with tunable curvature controlled by the irradiation time. Following by a secondary ionic cross-linking, the hydrogels are mechanically strengthened for practical microlens replication. Consequently, microlens arrays with a roughness around 20 nm are rapidly molded from the hydrogel templates. Multiple focuses are uniformly projected on a targeted plane, indicating the fine imaging capability of the microlenses. Moreover, the focal lengths are facilely adjustable not only in a wide range but also in a spatially selective manner. Our growth strategy paves a versatile and efficient method for the flexible fabrication of functional optical devices.

The production of active pharmaceutical ingredients (APIs) requires enantiopure chiral amines, for which greener synthesis processes are needed. Transaminases (TAs) are enzymes that catalyze the enantioselective production of chiral amines from prochiral ketones through transamination under mild conditions. Yet, industrial applications of biocatalytic transamination remain currently hindered by the limited stability of soluble enzymes and by the unfavorable thermodynamic equilibrium of targeted asymmetric reactions. Enzyme immobilization can be applied to address stability, recoverability, and reusability issues. In the perspective of process intensification, we chose to immobilize TAs on polymeric (polypropylene) membranes. In the asymmetric synthesis of (R)-2-fluoro-α-methylbenzylamine ((R)-FMBA), such membrane-immobilized TAs exhibited superior specific activity and stability compared with soluble TAs; they also outperformed TAs immobilized on resins. The reaction yield remained, however, limited by thermodynamics. To further enhance the synthesis yield, the reaction was coupled with the in situ crystallization of (R)-FMBA with 3,3-diphenylpropionic acid (DPPA). By doing so, the theoretical equilibrium conversion was pushed from ∼44% to ∼83%. In fact, a 72% overall recovery yield of crystallized (R)-FMBA was demonstrated. The enantioselectivity of the reaction mixture was preserved. Importantly, purification was greatly facilitated since the target enantiopure amine was readily recovered as high-purity (R)-FMBA:DPPA crystals. The biocatalytic membranes were found to be fully reusable, performing successive high-yield asymmetric syntheses with only minor deactivation. Overall, the crystallization-assisted strategy proposed herein offers a greener path for the biocatalytic production of valuable chiral targets.