Drug delivery systems that can control drug release profile to ensure a high therapeutic efficacy and reduced side effects are highly desired in pharmaceutical and biomedical fields. Microparticles are the most commonly used drug delivery systems, because they can be easily administrated to patients, and be engineered with different structures and functions for keeping drug stability, delivering drugs to a desired location, and releasing drugs with a predetermined rate in a well‐controlled manner. Microfluidic techniques show great power for controllable generation of highly monodisperse multiple emulsion droplets with unprecedented structural diversity. Microfluidics‐templated emulsions allow elaborately design and controllable generation of highly uniform microparticles with well‐controlled sizes, shapes, compositions, and structures, and integrated functions for controlled drug release. This review highlights recent progress on controllable microfluidic fabrication of monodisperse emulsion templates and the resultant polymeric microparticles with well‐tailored structures and functions for flexible encapsulation and controlled release of drugs. Especially, a comprehensive overview of the recent biomedical applications of these microparticles with diverse release mechanisms is provided. Finally, perspectives on further advancing the microfluidic techniques for fabricating functional microparticles from lab scale to industrial scale are discussed.

In this study, a novel class of multifunctional responsive nanoparticles is designed and fabricated as drug nanocarriers for synergetic chemo–photothermal therapy of tumors. The proposed nanoparticles are composed of a thermo-/pH-responsive poly­(N-isopropylacrylamide-co-acrylic acid) (PNA) nanogel core, a polydopamine (PDA) layer for photothermal conversion, and an outer folic acid (FA) layer as a targeting agent for the folate receptors on tumor cells. The fabricated nanoparticles show good biocompatibility and outstanding photothermal conversion efficiency. The proposed nanoparticles loaded with doxorubicin (DOX) drug molecules are stable under physiological conditions with low leakage of drugs, while rapidly release drugs in environments with low pH conditions and at high temperature. The experimental results show that the drug release process is mainly governed by Fickian diffusion. In vitro cell experimental results demonstrate that the PNA–DOX@PDA–FA nanoparticles can be phagocytized by 4T1 tumor cells and release drugs in tumor cell acidic environments, and confirm that the combined chemo and photothermal therapeutic efficacy of PNA–DOX@PDA–FA nanoparticles is higher than the photothermal therapeutic efficacy or the chemotherapeutic efficacy alone. The proposed multifunctional responsive nanoparticles in this study provide a novel class of drug nanocarriers as a promising tool for synergetic chemo–photothermal therapy of tumors.

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A smart diffraction grating immunosensor based on antigen-responsive hydrogel with enhanced analyte-induced volume changes is developed for highly selective and sensitive detection of human immunoglobulin G (H-IgG). The hydrogel grating contains poly(N-isopropylacrylamide) (PNIPAM) backbones with dual-cross-linking based on the dynamic complexation between pendent goat-anti-human IgG (GAH-IgG) and pendent H-IgG, and the covalent bonding by 4-arm-polyethylene glycol-acrylamide. Upon recognizing free H-IgG in the environment, the pendent GAH-IgG in the hydrogel can form new GAH-IgG/H-IgG complexes with free H-IgG because the binding constant of GAH-IgG to the free H-IgG is much larger than that of GAH-IgG to the pendent H-IgG and thus result in the decomplexation of GAH-IgG/H-IgG complexes with the pendent H-IgG as well as the swelling of hydrogel. The thermo-responsive PNIPAM backbones enable enhancement of H-IgG-responsive volume change of the proposed hydrogel grating via temperature regulation. Moreover, the cross-linker 4-arm-polyethylene glycol-acrylamide provides excellent transparency for the PNIPAM backbones during the volume change, which ensures output of diffracted optical signals with high intensity. With the elaborately designed molecular structures, the hydrogel grating allows highly selective and sensitive detection of [H-IgG] with a detection limit as low as 1.3 × 10 −8 M. This work provides a simple and flexible strategy for developing diffraction grating immunosensors based on stimuli-responsive hydrogels for efficient detection of biomarkers.