Fabrication of pH-responsive monodisperse microcapsules using interfacial tension of immiscible phases

Programmable Photoswitchable Microcapsules Enable Precise and Tailored Drug Delivery from Microfluidics

The development of precision personalized medicine poses a significant need for the next generation of advanced diagnostic and therapeutic technologies, and one of the key challenges is the development of highly time-, space-, and dose-controllable drug delivery systems that respond to the complex physiopathology of patient populations. In response to this challenge, an increasing number of stimuli-responsive smart materials are integrated into biomaterial systems for precise targeted drug delivery. Among them, responsive microcapsules prepared by droplet microfluidics have received much attention. In this study, we present a UV-visible light cycling mediated photoswitchable microcapsule (PMC) with dynamic permeability-switching capability for precise and tailored drug release. The PMCs were fabricated using a programmable pulsed aerodynamic printing (PPAP) technique, encapsulating an aqueous core containing magnetic nanoparticles and the drug doxorubicin (DOX) within a poly(lactic-co-glycolic acid) (PLGA) composite shell modified by PEG-b-PSPA. Selective irradiation of PMCs with ultraviolet (UV) or visible light (Vis) allows for high-precision time-, space-, and dose-controlled release of the therapeutic agent. An experimentally validated theoretical model was developed to describe the drug release pattern, holding promise for future customized programmable drug release applications. The therapeutic efficacy and value of patternable cancer cell treatment activated by UV radiation is demonstrated by our experimental results. After in vitro transcatheter arterial chemoembolization (TACE), PMCs can be removed by external magnetic fields to mitigate potential side effects. Our findings demonstrate that PMCs have the potential to integrate embolization, on-demand drug delivery, magnetic actuation, and imaging properties, highlighting their immense potential for tailored drug delivery and embolic therapy.

Recent advances in the microfluidic production of functional microcapsules by multiple-emulsion templating

Multiple-emulsion drops serve as versatile templates to design functional microcapsules due to their core-shell geometry and multiple compartments. Microfluidics has been used for the elaborate production of multiple-emulsion drops with a controlled composition, order, and dimensions, elevating the value of multiple-emulsion templates. Moreover, recent advances in the microfluidic control of the emulsification and parallelization of drop-making junctions significantly enhance the production throughput for practical use. Metastable multiple-emulsion drops are converted into stable microcapsules through the solidification of selected phases, among which solid shells are designed to function in a programmed manner. Functional microcapsules are used for the storage and release of active materials as drug carriers. Beyond their conventional uses, microcapsules can serve as microcompartments responsible for transmembrane communication, which is promising for their application in advanced microreactors, artificial cells, and microsensors. Given that post-processing provides additional control over the composition and construction of multiple-emulsion drops, they are excellent confining geometries to study the self-assembly of colloids and liquid crystals and produce miniaturized photonic devices. This review article presents the recent progress and current state of the art in the microfluidic production of multiple-emulsion drops, functionalization of solid shells, and applications of microcapsules.

Microfluidic macroemulsion stabilization through in situ interfacial coacervation of associative nanoplatelets and polyelectrolytes

HYPOTHESIS

Since macroemulsions tend to break down to lower free energy, they hardly retain their initial drop state. Therefore, studies are being conducted to overcome this based on advanced interface engineering techniques, but it is still challenging. Herein we hypothesize that the stability of giant droplets can be secured without chemical bonding through the interfacial coacervation of polyelectrolyte and associative nanoplatelets.

EXPERIMENTS

We synthesized associative silica nanoplates (ASNPs) via polypeptide-templated silicification and consecutive wettability adjustment. To produce monodisperse macrodroplets, the inner fluid containing partially positively charged ASNPs and the outer fluid dissolving negatively charged polyacrylic acid (PAA) were coflowed through a capillary-based microfluidic channel.

FINDINGS

Dynamic interfacial tension and interfacial rheology measurements revealed that the migration of ASNPs and PAA from each phase to the interface led to the formation of a complex bilayered thin membrane with an enhanced interfacial modulus. In addition, we demonstrated that adjusting the surface properties of ASNPs by coupling a fluorochemical enabled the production of monodisperse fluorocarbon-in-oil-in-water double macroemulsions. These results highlighted the applicability of our microfluidics-based interfacial coacervation technology in the development of complex fluid products with visual differentiation and drug encapsulation.

From vesicles to materials: bioinspired strategies for fabricating hierarchically structured soft matter

Certain organisms including species of mollusks, polychaetes, onychophorans and arthropods produce exceptional polymeric materials outside their bodies under ambient conditions using concentrated fluid protein precursors. While much is understood about the structure-function relationships that define the properties of such materials, comparatively less is understood about how such materials are fabricated and specifically, how their defining hierarchical structures are achieved via bottom-up assembly. Yet this information holds great potential for inspiring sustainable manufacture of advanced polymeric materials with controlled multi-scale structure. In the present perspective, we first examine recent work elucidating the formation of the tough adhesive fibres of the mussel byssus via secretion of vesicles filled with condensed liquid protein phases (coacervates and liquid crystals)-highlighting which design principles are relevant for bio-inspiration. In the second part of the perspective, we examine the potential of recent advances in drops and additive manufacturing as a bioinspired platform for mimicking such processes to produce hierarchically structured materials. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)'.

Monodisperse Selectively Permeable Hydrogel Capsules Made from Single Emulsion Drops

Capsules are often used to protect chemical and biological entities from the environment, to control the timing and location of their release, or to facilitate the collection of waste. Their performance depends on the thickness and composition of their shells, which can be closely controlled if capsules are made from double emulsion drops that are produced with microfluidics. However, the fabrication of such double emulsions is delicate, limiting throughput and increasing costs. Here, a fast, scalable method to produce monodisperse microcapsules possessing mechanically robust, thin, semipermeable hydrogel shells from single emulsion drops is introduced. This is achieved by selectively polymerizing reagents in close proximity to the drop surface to form a biocompatible 1.6 μm-thick hydrogel shell that encompasses a liquid core. The size-selective permeability of the shell enables the growth of living yeast and bacteria in their cores. Moreover, if capsules are loaded with adsorbents, they can repetitively remove waste products from water. The simplicity and robustness of the capsule fabrication makes the process scalable and cost effective. It has thus the potential to extend the use of calibrated capsules possessing well-defined dimensions to cost sensitive fields, including food, waste water treatment, or oil recovery.