Controllable microfluidic fabrication of microstructured functional materials

A comparative analysis of PLA and PCL microparticles for hydrophilic and hydrophobic drugs

This study aims to investigate Polylactic Acid (PLA) and Polycaprolactone (PCL) polymers for microencapsulation of hydrophilic and hydrophobic anti-glaucoma drugs using an emulsion-based solvent evaporation technique. Microparticle size was analysed using optical microscopy, while drug-polymer interactions through Dynamic-Light-Scattering (DLS) and Fourier-Transform-Infra-red/Attenuated-Total-Reflection spectroscopy (FTIR/ATR). In vitro, drug release studies were performed to investigate drug encapsulation and release profiles. Spherical microparticles, with particle size 94 ± 6.9 μm for PCL-based and 100 ± 3.74 μm for PLA-based formulation, were obtained. Drug release studies showed 100% release over about 32 days, with encapsulation efficiency (%EE) and drug loading (%w/w) reaching up to 95 and 2.84% for PLA-based and 97 and 2.91% for PCL-based microparticles, respectively. DLS studies reveal an increase in hydrodynamic radius (RH), which correlates to enhanced drug encapsulation. So, the nature of the drug and polymer significantly impacts drug encapsulation and release, with drug-polymer interactions playing a crucial role alongside experimental parameters.

Unveiling the potentials of hydrophilic and hydrophobic polymers in microparticle systems: Opportunities and challenges in processing techniques

Conventional drug delivery systems are associated with various shortcomings, including low bioavailability and limited control over release. Biodegradable polymeric microparticles have emerged as versatile carriers in drug delivery systems addressing all these challenges. This comprehensive review explores the dynamic landscape of microparticles, considering the role of hydrophilic and hydrophobic materials. Within the continuously evolving domain of microparticle preparation methods, this review offers valuable insights into the latest advancements and addresses the factors influencing microencapsulation, which is pivotal for harnessing the full potential of microparticles. Exploration of the latest research in this dynamic field unlocks the possibilities of optimizing microencapsulation techniques to produce microparticles of desired characteristics and properties for different applications, which can help contribute to the ongoing evolution in the field of pharmaceutical science.

Revolutionizing targeting precision: microfluidics-enabled smart microcapsules for tailored delivery and controlled release

As promising delivery systems, smart microcapsules have garnered significant attention owing to their targeted delivery loaded with diverse active materials. By precisely manipulating fluids on the micrometer scale, microfluidic has emerged as a powerful tool for tailoring delivery systems based on potential applications. The desirable characteristics of smart microcapsules are associated with encapsulation capacity, targeted delivery capability, and controlled release of encapsulants. In this review, we briefly describe the principles of droplet-based microfluidics for smart microcapsules. Subsequently, we summarize smart microcapsules as delivery systems for efficient encapsulation and focus on target delivery patterns, including passive targets, active targets, and microfluidics-assisted targets. Additionally, based on release mechanisms, we review controlled release modes adjusted by smart membranes and on/off gates. Finally, we discuss existing challenges and potential implications associated with smart microcapsules.

Polymeric Based Hydrogel Membranes for Biomedical Applications

The development of biomedical applications is a transdisciplinary field that in recent years has involved researchers from chemistry, pharmacy, medicine, biology, biophysics, and biomechanical engineering. The fabrication of biomedical devices requires the use of biocompatible materials that do not damage living tissues and have some biomechanical characteristics. The use of polymeric membranes, as materials meeting the above-mentioned requirements, has become increasingly popular in recent years, with outstanding results in tissue engineering, for regeneration and replenishment of tissues constituting internal organs, in wound healing dressings, and in the realization of systems for diagnosis and therapy, through the controlled release of active substances. The biomedical application of hydrogel membranes has had little uptake in the past due to the toxicity of cross-linking agents and to the existing limitations regarding gelation under physiological conditions, but now it is proving to be a very promising field This review presents the important technological innovations that the use of membrane hydrogels has promoted, enabling the resolution of recurrent clinical problems, such as post-transplant rejection crises, haemorrhagic crises due to the adhesion of proteins, bacteria, and platelets on biomedical devices in contact with blood, and poor compliance of patients undergoing long-term drug therapies.

Ultrasound-trigged micro/nanorobots for biomedical applications

Micro- and nanorobots (MNRs) propelled by external actuations have broad potential in biomedical applications. Among the numerous external excitations, ultrasound (US) features outstanding practical significance with merits of its noninvasiveness, tunability, penetrability, and biocompatibility. Attributing to various physiochemical effects of US, it can propel the MNRs with sophisticated structures through asymmetric acoustic streaming, bubble oscillation, and so on. In this review, we introduce several advanced and representative US-propelled MNRs with inhomogeneous density distribution, asymmetric shape, hollow cavity, etc. The potential biomedical applications of these cutting-edge MNRs are also presented, including intracellular delivery, harmful substances collection, and so on. Furthermore, we conclude the advantages and limitations of US-propelled MNRs and prospect their future developments in multidisciplinary fields.

Toward droplets displaying life-like interaction behaviors

Developments in synthetic biology usually bring the conception of individual artificial cells. A key feature of living systems is, however, the interaction between individuals, in which living units can interact autonomously and display a role differentiation such as the case of entities chasing each other. On the other hand, droplets have become a very useful and exciting medium for modern microengineering and biomedical technologies. In this Perspective, we show a brief discussion-outlook of different approaches to recreate predator-prey interactions in both swimmer and crawling droplet systems toward a new generation of synthetic life with impact in both fundamental insights and relevant applications.

Microfluidic Formulation of Topological Hydrogels for Microtissue Engineering

Microfluidics has recently emerged as a powerful tool in generation of submillimeter-sized cell aggregates capable of performing tissue-specific functions, so-called microtissues, for applications in drug testing, regenerative medicine, and cell therapies. In this work, we review the most recent advances in the field, with particular focus on the formulation of cell-encapsulating microgels of small "dimensionalities": "0D" (particles), "1D" (fibers), "2D" (sheets), etc., and with nontrivial internal topologies, typically consisting of multiple compartments loaded with different types of cells and/or biopolymers. Such structures, which we refer to as topological hydrogels or topological microgels (examples including core-shell or Janus microbeads and microfibers, hollow or porous microstructures, or granular hydrogels) can be precisely tailored with high reproducibility and throughput by using microfluidics and used to provide controlled "initial conditions" for cell proliferation and maturation into functional tissue-like microstructures. Microfluidic methods of formulation of topological biomaterials have enabled significant progress in engineering of miniature tissues and organs, such as pancreas, liver, muscle, bone, heart, neural tissue, or vasculature, as well as in fabrication of tailored microenvironments for stem-cell expansion and differentiation, or in cancer modeling, including generation of vascularized tumors for personalized drug testing. We review the available microfluidic fabrication methods by exploiting various cross-linking mechanisms and various routes toward compartmentalization and critically discuss the available tissue-specific applications. Finally, we list the remaining challenges such as simplification of the microfluidic workflow for its widespread use in biomedical research, bench-to-bedside transition including production upscaling, further in vivo validation, generation of more precise organ-like models, as well as incorporation of induced pluripotent stem cells as a step toward clinical applications.

Systematic characterization of effect of flow rates and buffer compositions on double emulsion droplet volumes and stability

Double emulsion droplets (DEs) are water/oil/water droplets that can be sorted via fluorescence-activated cell sorting (FACS), allowing for new opportunities in high-throughput cellular analysis, enzymatic screening, and synthetic biology. These applications require stable, uniform droplets with predictable microreactor volumes. However, predicting DE droplet size, shell thickness, and stability as a function of flow rate has remained challenging for monodisperse single core droplets and those containing biologically-relevant buffers, which influence bulk and interfacial properties. As a result, developing novel DE-based bioassays has typically required extensive initial optimization of flow rates to find conditions that produce stable droplets of the desired size and shell thickness. To address this challenge, we conducted systematic size parameterization quantifying how differences in flow rates and buffer properties (viscosity and interfacial tension at water/oil interfaces) alter droplet size and stability, across 6 inner aqueous buffers used across applications such as cellular lysis, microbial growth, and drug delivery, quantifying the size and shell thickness of >22 000 droplets overall. We restricted our study to stable single core droplets generated in a 2-step dripping-dripping formation regime in a straightforward PDMS device. Using data from 138 unique conditions (flow rates and buffer composition), we also demonstrated that a recent physically-derived size law of Wang et al. can accurately predict double emulsion shell thickness for >95% of observations. Finally, we validated the utility of this size law by using it to accurately predict droplet sizes for a novel bioassay that requires encapsulating growth media for bacteria in droplets. This work has the potential to enable new screening-based biological applications by simplifying novel DE bioassay development.

Biodegradable Microparticles for Regenerative Medicine: A State of the Art and Trends to Clinical Application

Tissue engineering and cell therapy are very attractive in terms of potential applications but remain quite challenging regarding the clinical aspects. Amongst the different strategies proposed to facilitate their implementation in clinical practices, biodegradable microparticles have shown promising outcomes with several advantages and potentialities. This critical review aims to establish a survey of the most relevant materials and processing techniques to prepare these micro vehicles. Special attention will be paid to their main potential applications, considering the regulatory constraints and the relative easiness to implement their production at an industrial level to better evaluate their application in clinical practices.