Uniform polymer microspheres: monodispersity criteria, methods of formation and applications

Complex Emulsions as an Innovative Pharmaceutical Dosage form in Addressing the Issues of Multi-Drug Therapy and Polypharmacy Challenges

This review explores the intersection of microfluidic technology and complex emulsion development as a promising solution to the challenges of formulations in multi-drug therapy (MDT) and polypharmacy. The convergence of microfluidic technology and complex emulsion fabrication could herald a transformative era in multi-drug delivery systems, directly confronting the prevalent challenges of polypharmacy. Microfluidics, with its unparalleled precision in droplet formation, empowers the encapsulation of multiple drugs within singular emulsion particles. The ability to engineer emulsions with tailored properties-such as size, composition, and release kinetics-enables the creation of highly efficient drug delivery vehicles. Thus, this innovative approach not only simplifies medication regimens by significantly reducing the number of necessary doses but also minimizes the pill burden and associated treatment termination-issues associated with polypharmacy. It is important to bring forth the opportunities and challenges of this synergy between microfluidic-driven complex emulsions and multi-drug therapy poses. Together, they not only offer a sophisticated method for addressing the intricacies of delivering multiple drugs but also align with broader healthcare objectives of enhancing treatment outcomes, patient safety, and quality of life, underscoring the importance of dosage form innovations in tackling the multifaceted challenges of modern pharmacotherapy.

Recent Progress of Droplet Microfluidic Emulsification Based Synthesis of Functional Microparticles

The remarkable control function over the functional material formation process enabled by droplet microfluidic emulsification approaches can lead to the efficient and one-step encapsulation of active substances in microparticles, with the microparticle characteristics well regulated. In comparison to the conventional fabrication methods, droplet microfluidic technology can not only construct microparticles with various shapes, but also provide excellent templates, which enrich and expand the application fields of microparticles. For instance, intersection with disciplines in pharmacy, life sciences, and others, modifying the structure of microspheres and appending functional materials can be completed in the preparation of microparticles. The as-prepared polymer particles have great potential in a wide range of applications for chemical analysis, heavy metal adsorption, and detection. This review systematically introduces the devices and basic principles of particle preparation using droplet microfluidic technology and discusses the research of functional microparticle formation with high monodispersity, involving a plethora of types including spherical, nonspherical, and Janus type, as well as core-shell, hole-shell, and controllable multicompartment particles. Moreover, this review paper also exhibits a critical analysis of the current status and existing challenges, and outlook of the future development in the emerging fields has been discussed.

Amphiphilic Polypeptides Obtained by the Post-Polymerization Modification of Poly(Glutamic Acid) and Their Evaluation as Delivery Systems for Hydrophobic Drugs

Synthetic poly(amino acids) are a unique class of macromolecules imitating natural polypeptides and are widely considered as carriers for drug and gene delivery. In this work, we synthesized, characterized and studied the properties of amphiphilic copolymers obtained by the post-polymerization modification of poly(α,L-glutamic acid) with various hydrophobic and basic L-amino acids and D-glucosamine. The resulting glycopolypeptides were capable of forming nanoparticles that exhibited reduced macrophage uptake and were non-toxic to human lung epithelial cells (BEAS-2B). Moreover, the developed nanoparticles were suitable for loading hydrophobic cargo. In particular, paclitaxel nanoformulations had a size of 170-330 nm and demonstrated a high cytostatic efficacy against human lung adenocarcinoma (A549). In general, the obtained nanoparticles were comparable in terms of their characteristics and properties to those based on amphiphilic (glyco)polypeptides obtained by copolymerization methods.

Designable Micro-/Nano-Structured Smart Polymeric Materials

Smart polymeric materials with dynamically tunable physico-chemical characteristics in response to changes of environmental stimuli, have received considerable attention in myriad fields. The diverse combination of their micro-/nano-structural and molecular designs creates promising and exciting opportunities for exploiting advanced smart polymeric materials. Engineering micro-/nano-structures into smart polymeric materials with elaborate molecular design enables intricate coordination between their structures and molecular-level response to cooperatively realize smart functions for practical applications. In this review, recent progresses of smart polymeric materials that combine micro-/nano-structures and molecular design to achieve designed advanced functions are highlighted. Smart hydrogels, gating membranes, gratings, milli-particles, micro-particles and microvalves are employed as typical examples to introduce their design and fabrication strategies. Meanwhile, the key roles of interplay between their micro-/nano-structures and responsive properties to realize the desired functions for their applications are emphasized. Finally, perspectives on the current challenges and opportunities of micro-/nano-structured smart polymeric materials for their future development are presented.

Single cell multi-miRNAs quantification with hydrogel microbeads for liver cancer cell subtypes discrimination

The simultaneous quantification of multi-miRNAs in single cells reveals cellular heterogeneity, and benefits the subtypes discrimination of cancer cells . Though micro-droplet techniques enable successful single cell encapsulation, the isolated and restricted reaction space of microdroplets causes cross-reactions and inaccuracy for simultaneous multi-miRNAs quantification. Herein, we develop a hydrogel microbead based strategy for the simultaneous sensitive quantification of miRNA-21, 122 and 222 in single cells. Single cells are encapsulated and undergo cytolysis in hydrogel microbeads. The three target miRNAs are retained in the microbead by pre-immobilized capture probes, and activate rolling circle amplification (RCA) reactions. The RCA products are hybridized with corresponding dye labelled DNA reporters, and the respective fluorescence intensities are recorded for multi-miRNA quantification. The porous structure of the hydrogel microbeads allows the free diffusion of reactants and easy removal of unreacted DNA strands, which effectively avoids nonspecific cross-reactions. Clear differentiation of cellular heterogeneity and subpopulation discrimination are achieved for three kinds of liver cancer cells and one normal liver cell.

A single cell multi-miRNAs quantification strategy is reported. Single cells are encapsulated and undergo cytolysis in hydrogel microbeads, then the quantitative analysis of three miRNAs is used to achieve sub-populations discrimination for liver cells.

Solvent-free preparation of uniform styrene/maleimide copolymer microspheres from solid poly(styrene-alt-maleic anhydride) microspheres

A solvent-free strategy to prepare poly(styrene-alt-maleimide) (SMI) provides a facile and environmentally friendly pathway to a large-scale low cost production of monodisperse SMI microspheres.

Droplet microfluidic devices for organized stem cell differentiation into germ cells: capabilities and challenges

Demystifying the mechanisms that underlie germline development and gamete production is critical for expanding advanced therapies for infertile couples who cannot benefit from current infertility treatments. However, the low number of germ cells, particularly in the early stages of development, represents a serious challenge in obtaining sufficient materials required for research purposes. In this regard, pluripotent stem cells (PSCs) have provided an opportunity for producing an unlimited source of germ cells in vitro. Achieving this ambition is highly dependent on accurate stem cell niche reconstitution which is achievable through applying advanced cell engineering approaches. Recently, hydrogel microparticles (HMPs), as either microcarriers or microcapsules, have shown promising potential in providing an excellent 3-dimensional (3D) biomimetic microenvironment alongside the systematic bioactive agent delivery. In this review, recent studies of utilizing various HMP-based cell engineering strategies for appropriate niche reconstitution and efficient in vitro differentiation are highlighted with a special focus on the capabilities of droplet-based microfluidic (DBM) technology. We believe that a deep understanding of the current limitations and potentials of the DBM systems in integration with stem cell biology provides a bright future for germ cell research.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12551-021-00907-5.

Long-acting injectable donepezil microspheres: Formulation development and evaluation

Novel formulations of donepezil (DNP)-loaded microspheres based on a bio-degradable polymer of poly(lactic-co-glycolic acid) (PLGA) with a one-month duration of effect were developed, aimed at reducing dosing frequency and adverse effects and improving patient adherence. The spherical and monodispersed DNP-loaded microspheres were precisely fabricated by the Inventage Lab Precision Particle Fabrication method (IVL-PPFM®) based on micro-electromechanical systems (MEMS) and microfluidic technology. The types of polymers and end-groups, the drug/polymer ratio (DPR), and the routes of administration for DNP were studied to ensure an effective concentration and desired duration. Laser-light particle size analysis and scanning electron microscopy were used to characterization. Also, non-clinical animal models of beagle dogs are used to optimize DNP formulations and evaluate their pharmacokinetic properties. The PK results showed that the DPR was a critical factor in determining the exposure level and duration of DNR release. Furthermore, the lactide ratio, which varied depending upon the type of polymer, determined the hydrophobic interaction and was also an important factor affecting the desired DNP release. Since DNP shows a large inter-species variation between dogs and humans, PK modeling and simulation of the reference drug (i.e., Aricept®) and DNP-loaded microspheres were used for formulation development to overcome and interpret these variations. In addition, the developed PK model was extrapolated to humans using the estimated PK parameter and published clinical pharmacology data for DNP. The predicted PK profile of the DNP-loaded microsphere in humans showed that the formulation with PLGA 7525A and the DPR of 1/9 could maintain drug concentration for a month and could control initial burst release. The data obtained from the study could be used as scientific evidence for decision-making in future formulation development.

Poly[2-(dimethylamino)ethyl methacrylate-co-ethylene dimethacrylate]nanogel by dispersion polymerization for inhibition of pathogenic bacteria

Bacterial infections and antimicrobial resistance are one of the major public health problems and various strategies to prevent potential threats have been developed. Protonated polymers were proven as efficient agents against several microbial pathogens. Poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) linear polymer and its copolymers represent one example of functional materials which inhibit the growth of both harmful Gram-negative and Gram-positive bacteria. However, the antimicrobial effect of positively charged PDMAEMA particles has been never tested. In this report, we deeply studied several parameters of free-radical polymerization, including the effect of crosslinking monomer, medium composition, solvency and polarity, and type and concentration of initiator and stabilizer, to fabricate high-quality poly[2-(dimethylamino)ethyl methacrylate-co-ethylene dimethacrylate] (PDMAEMA-EDMA) nanogel. We successfully found that dispersion polymerization in water/2-methoxyethanol medium (80/20 w/w), initiated with 0.2 wt% potassium persulfate (KPS) and stabilized with 0.5 wt% poly(vinyl alcohol) (PVA), produced a well-defined and sub-micron 167 nm PDMAEMA-EDMA nanogel. Bactericidal activity of the quaternized PDMAEMA-EDMA nanogel was assessed via time-kill curve assay against two Gram-positive and Gram-negative pathogenic bacteria, namely Staphylococcus aureus (S. aureus) and Acinetobacter baumannii (A. baumannii). The results illustrated that the quaternized PDMAEMA-EDMA nanogel acted as an effective bactericidal agent against both tested bacteria.

Biodegradable Polymer Microparticles with Tunable Shapes and Surface Textures for Enhancement of Dendritic Cell Maturation

In this report, we present a facile approach to produce biodegradable polymeric microparticles with uniform sizes and controllable morphologies by blending hydrophobic poly(d, l-lactic-co-glycolide) (PLGA) and amphiphilic poly(d, l-lactic acid)-b-poly(ethylene glycol) (PLA-b-PEG) in a microfluidic chip. Microparticles with tentacular, hollow hemispherical, and Janus structures were obtained after complete evaporation of the organic solvent by manipulating the interfacial behavior of emulsion droplets and the phase separation behavior inside the droplets. The number and length of the tentacles on the surface of tentacular microparticles could be tailored by varying the initial concentration and blending ratios of the polymers. The organic solvent played an important role in controlling the morphologies of microparticles. For example, blending PLA_16k-b-PEG_5k with PLGA_100k in dichloromethane resulted in tentacular microparticles, whereas hollow hemispherical microparticles were obtained in trichloromethane. Moreover, these microparticles with controllable shapes and surface textures have significant influence on the immune response of dendritic cells (DCs), showing a morphology-dependent enhancement of DC maturation.

Protocol for Determining Ultraviolet Light Emitting Diode (UV-LED) Fluence for Microbial Inactivation Studies

Determining fluence is essential to derive the inactivation kinetics of microorganisms and to design ultraviolet (UV) reactors for water disinfection. UV light emitting diodes (UV-LEDs) are emerging UV sources with various advantages compared to conventional UV lamps. Unlike conventional mercury lamps, no standard method is available to determine the average fluence of the UV-LEDs, and conventional methods used to determine the fluence for UV mercury lamps are not applicable to UV-LEDs due to the relatively low power output, polychromatic wavelength, and specific radiation profile of UV-LEDs. In this study, a method was developed to determine the average fluence inside a water suspension in a UV-LED experimental setup. In this method, the average fluence was estimated by measuring the irradiance at a few points for a collimated and uniform radiation on a Petri dish surface. New correction parameters were defined and proposed, and several of the existing parameters for determining the fluence of the UV mercury lamp apparatus were revised to measure and quantify the collimation and uniformity of the radiation. To study the effect of polychromatic output and radiation profile of the UV-LEDs, two UV-LEDs with peak wavelengths of 262 and 275 nm and different radiation profiles were selected as the representatives of typical UV-LEDs applied to microbial inactivation. The proper setup configuration for microorganism inactivation studies was also determined based on the defined correction factors.

Trojan-Horse-Like Stimuli-Responsive Microcapsules

Multicompartment microcapsules, with each compartment protected by a distinct stimuli-responsive shell for versatile controlled release, are highly desired for developing new-generation microcarriers. Although many multicompartmental microcapsules have been created, most cannot combine different release styles to achieve flexible programmed sequential release. Here, one-step template synthesis of controllable Trojan-horse-like stimuli-responsive microcapsules is reported with capsule-in-capsule structures from microfluidic quadruple emulsions for diverse programmed sequential release. The nested inner and outer capsule compartments can separately encapsulate different contents, while their two stimuli-responsive hydrogel shells can individually control the content release from each capsule compartment for versatile sequential release. This is demonstrated by using three types of Trojan-horse-like stimuli-responsive microcapsules, with different combinations of release styles for flexible programmed sequential release. The proposed microcapsules provide novel advanced candidates for developing new-generation microcarriers for diverse, efficient applications.

Efficient targeted tumor imaging and secreted endostatin gene delivery by anti-CD105 immunoliposomes

BACKGROUND

Anti-CD105 mAb-conjugated immunoliposomes, loaded with secreted mouse endostatin gene, were developed for targeted tumor imaging and antiangiogenic gene therapy.

METHODS

The liposomes were investigated for size, zeta-potential, lipid content, antibody binding ability, and pcDNA loading capacity. The ability of immunoliposomes to target tumor-derived endothelial cells and perform gene transfer in vitro was measured and their basic biocompatibility was evaluated. A nude mouse/breast cancer xenograft model was used to examine the tumor internalization of fluorescent-labeled liposomes and the clinical potential of immnuoliposomes loaded with pcDNA3.1-CSF1-endostatin.

RESULTS

Loaded immunoliposomes were homogenously distributed with a well-defined spherical shape and bilayer, diameter of 122 ± 11 nm, and zeta potential + 1.40 mV. No significant differences were observed in body weight, liver index, oxidative stress, or liver and kidney function in mice after liposomes exposure. The addition of CD105 mAb to liposomes conferred the ability to target tumor-derived endothelial cells in vitro and in vivo. Systemic intravenous administration of fluorescent immunoliposomes in the xenograft model resulted in selective and efficient internalization in tumor vasculature. Treatment of mice with pcDNA3.1-CSF1-endostatin-loaded immunoliposomes suppressed tumor growth by 71%.

CONCLUSIONS

These data demonstrate the advantages of using anti-CD105 mAb-conjugated immunoliposomes to enhance tumor targeting, imaging, and gene transfer applications.

Deterministic encapsulation of single cells in thin tunable microgels for niche modelling and therapeutic delivery

Existing techniques to encapsulate cells into microscale hydrogels generally yield high polymer-to-cell ratios and lack control over the hydrogel's mechanical properties. Here, we report a microfluidic-based method for encapsulating single cells in an approximately six-micrometre layer of alginate that increases the proportion of cell-containing microgels by a factor of ten, with encapsulation efficiencies over 90%. We show that in vitro cell viability was maintained over a three-day period, that the microgels are mechanically tractable, and that, for microscale cell assemblages of encapsulated marrow stromal cells cultured in microwells, osteogenic differentiation of encapsulated cells depends on gel stiffness and cell density. We also show that intravenous injection of singly encapsulated marrow stromal cells into mice delays clearance kinetics and sustains donor-derived soluble factors in vivo. The encapsulation of single cells in tunable hydrogels should find use in a variety of tissue engineering and regenerative medicine applications.

Degradation, intra-articular retention and biocompatibility of monospheres composed of [PDLLA-PEG-PDLLA]-b-PLLA multi-block copolymers

In this study, we investigated the use of microspheres with a narrow particle size distribution ('monospheres') composed of biodegradable poly(DL-lactide)-PEG-poly(DL-lactide)-b-poly(L-lactide) multiblock copolymers that are potentially suitable for local sustained drug release in articular joints. Monospheres with sizes of 5, 15 and 30μm and a narrow particle size distribution were prepared by a micro-sieve membrane emulsification process. During in vitro degradation, less crystallinity, higher swelling and accelerated mass loss during was observed with increasing the PEG content of the polymer. The monospheres were tested in both a small (mice/rat) and large animal model (horse). In vivo imaging after injection with fluorescent dye loaded microspheres in mice knees showed that monospheres of all sizes retained within the joint for at least 90days, while the same dose of free dye redistributed to the whole body within the first day after intra-articular injection. Administration of monospheres in equine carpal joints caused a mild transient inflammatory response without any clinical signs and without degradation of the cartilage, as evidenced by the absence of degradation products of sulfated glycosaminoglycans or collagen type 2 in the synovial fluid. The excellent intra-articular biocompatibility was confirmed in rat knees, where μCT-imaging and histology showed neither changes in cartilage quality nor quantity. Given the good intra-articular retention and the excellent biocompatibility, these novel poly(DL-lactide)-PEG-poly(DL-lactide)-b-poly(L-lactide)-based monospheres can be considered a suitable platform for intra-articular drug delivery.

STATEMENT OF SIGNIFICANCE

This paper demonstrates the great potential in intra-articular drug delivery of monodisperse biodegradable microspheres which were prepared using a new class of biodegradable multi-block copolymers and a unique membrane emulsification process allowing the preparation of microspheres with a narrow particle size distribution (monospheres) leading to multiple advantages like better injectability, enhanced reproducibility and predictability of the in vivo release kinetics. We report not only on the synthesis and preparation, but also in vitro characterization, followed by in vivo testing of intra-articular biocompatibility of the monospheres in both a small and a large animal model. The favourable intra-articular biocompatibility combined with the prolonged intra-articular retention (>90days) makes these monospheres an interesting drug delivery platform. What should also be highlighted is the use of horses; a very accurate translational model for the human situation, making the results not only relevant for equine healthcare, but also for the development of novel human OA therapies.

Manufacture of poly(methyl methacrylate) microspheres using membrane emulsification

Accurate control of particle size at relatively narrow polydispersity remains a key challenge in the production of synthetic polymer particles at scale. A cross-flow membrane emulsification (XME) technique was used here in the preparation of poly(methyl methacrylate) microspheres at a 1-10 l h(-1) scale, to demonstrate its application for such a manufacturing challenge. XME technology has previously been shown to provide good control over emulsion droplet sizes with careful choice of the operating conditions. We demonstrate here that, for an appropriate formulation, equivalent control can be gained for a precursor emulsion in a batch suspension polymerization process. We report here the influence of key parameters on the emulsification process; we also demonstrate the close correlation in size between the precursor emulsion and the final polymer particles. Two types of polymer particle were produced in this work: a solid microsphere and an oil-filled matrix microcapsule.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.

Core-Shell Chitosan Microcapsules for Programmed Sequential Drug Release

A novel type of core-shell chitosan microcapsule with programmed sequential drug release is developed by the microfluidic technique for acute gastrosis therapy. The microcapsule is composed of a cross-linked chitosan hydrogel shell and an oily core containing both free drug molecules and drug-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles. Before exposure to acid stimulus, the resultant microcapsules can keep their structural integrity without leakage of the encapsulated substances. Upon acid-triggering, the microcapsules first achieve burst release due to the acid-induced decomposition of the chitosan shell. The encapsulated free drug molecules and drug-loaded PLGA nanoparticles are rapidly released within 60 s. Next, the drugs loaded in the PLGA nanoparticles are slowly released for several days to achieve sustained release based on the synergistic effect of drug diffusion and PLGA degradation. Such core-shell chitosan microcapsules with programmed sequential drug release are promising for rational drug delivery and controlled-release for the treatment of acute gastritis. In addition, the microcapsule systems with programmed sequential release provide more versatility for controlled release in biomedical applications.

Liposome-mediated delivery of the p21 activated kinase-1 (PAK-1) inhibitor IPA-3 limits prostate tumor growth in vivo

P21 activated kinases-1 (PAK-1) is implicated in various diseases. It is inhibited by the small molecule 'inhibitor targeting PAK1 activation-3' (IPA-3), which is highly specific but metabolically unstable. To address this limitation we encapsulated IPA-3 in sterically stabilized liposomes (SSL). SSL-IPA-3 averaged 139nm in diameter, polydispersity index (PDI) of 0.05, and a zeta potential of -28.1, neither of which changed over 14days; however, the PDI increased to 0.139. Analysis of liposomal IPA-3 levels demonstrated good stability, with 70% of IPA-3 remaining after 7days. SSL-IPA-3 inhibited prostate cancer cell growth in vitro with comparable efficacy to free IPA-3. Excitingly, only a 2day/week dose of SSL-IPA-3 was needed to inhibit the growth of prostate xenografts in vivo, while a similar dose of free IPA-3 was ineffective. These data demonstrate the development and clinical utility of a novel liposomal formulation for the treatment of prostate cancer.

Uniform Microparticles with Controllable Highly Interconnected Hierarchical Porous Structures

A simple and versatile strategy is developed for one-step fabrication of uniform polymeric microparticles with controllable highly interconnected hierarchical porous structures. Monodisperse water-in-oil-in-water (W/O/W) emulsions, with methyl methacrylate, ethylene glycol dimethacrylate, and glycidyl methacrylate as the monomer-containing oil phase, are generated from microfluidics and used for constructing the microparticles. Due to the partially miscible property of oil/aqueous phases, the monodisperse W/O/W emulsions can deform into desired shapes depending on the packing structure of inner aqueous microdrops, and form aqueous nanodrops in the oil phase. The deformed W/O/W emulsions allow template syntheses of highly interconnected hierarchical porous microparticles with precisely and individually controlled pore size, porosity, functionality, and particle shape. The microparticles elaborately combine the advantages of enhanced mass transfer, large functional surface area, and flexibly tunable functionalities, providing an efficient strategy to physically and chemically achieve enhanced synergetic performances for extensive applications. This is demonstrated by using the microparticles for oil removal for water purification and protein adsorption for bioseparation. The method proposed in this study provides full versatility for fabrication of functional polymeric microparticles with controllable hierarchical porous structures for enhancing and even broadening their applications.

Utilization of nanoparticles as X-ray contrast agents for diagnostic imaging applications

Among all the diagnostic imaging modalities, X-ray imaging techniques are the most commonly used owing to their high resolution and low cost. The improvement of these techniques relies heavily on the development of novel X-ray contrast agents, which are molecules that enhance the visibility of internal structures within the body in X-ray imaging. To date, clinically used X-ray contrast agents consist mainly of small iodinated molecules that might cause severe adverse effects (e.g. allergies, cardiovascular diseases and nephrotoxicity) in some patients owing to the large and repeated doses that are required to achieve good contrast. For this reason, there is an increasing interest in the development of alternative X-ray contrast agents utilizing elements with high atomic numbers (e.g. gold, bismuth, ytterbium and tantalum), which are well known for exhibiting high absorption of X-rays. Nanoparticles (NPs) made from these elements have been reported to have better imaging properties, longer blood circulation times and lower toxicity than conventional iodinated X-ray contrast agents. Additionally, the combination of two or more of these elements into a single carrier allows for the development of multimodal and hybrid contrast agents. Herein, the limitations of iodinated X-ray contrast agents are discussed and the parameters that influence the efficacy of X-ray contrast agents are summarized. Several examples of the design and production of both iodinated and iodine-free NP-based X-ray contrast agents are then provided, emphasizing the studies performed to evaluate their X-ray attenuation capabilities and their toxicity in vitro and in vivo.

Functional polymeric microparticles engineered from controllable microfluidic emulsions

Functional polymeric microparticles with typical sizes of 1-1000 μm have received considerable attention for many applications. Especially in biomedical fields, polymeric microparticles with advanced functions such as targeted delivery, controlled encapsulation, or "capture and release" show great importance as delivery systems for active molecules and drugs, as imaging agents for analytics and diagnostics, as microreactors for confined bioreactions, and more. Generally, the functions of these microparticles rely on both their structures and the properties of their component materials. Thus, creating unique structures from functional materials provides an important strategy for developing advanced functional polymeric microparticles. Several methods, such as dispersion polymerization, precipitation polymerization, copolymer self-assembly, and phase-separated polymer precipitation can be used to make functional microparticles, but each has limitations, for example, their limited control over the particle size and structure. Using emulsions as templates, however, allows precise control over the size, shape, composition, and structure of the resulting microparticles by tuning those of the emulsions via specific emulsification techniques. Microfluidic methods offer excellent control of emulsion droplets, thereby providing a powerful platform for continuous, reproducible, scalable production of polymeric microparticles with unprecedented control over their monodispersity, structures, and compositions. This approach provides broad opportunities for producing polymeric microparticles with novel structure-property combinations and elaborately designed functions. In this Account, we highlight recent efforts in microfluidic fabrication of advanced polymeric microparticles with well-designed functions for potential biomedical applications, and we describe the development of microfluidic techniques for producing monodisperse and versatile emulsion templates. We begin by describing microparticles made from single emulsions and then describe those from complex multiple emulsions, showing how the resulting microparticles combine novel structures and material properties to achieve their advanced functions. Monodisperse emulsions enable production of highly uniform microparticles of desired sizes to achieve programmed release rates and passive targeting for drug delivery and diagnostic imaging. Phase-separated multiple emulsions allow combination of a variety of functional materials to generate compartmental microparticles including hollow, core-shell, multicore-shell, and hole-shell structures for controlled encapsulation and release, selective capture, and confined bioreaction. We envision that the versatility of microfluidics for microparticle synthesis could open new frontiers and provide promising and exciting opportunities for fabricating new functional microparticles with broad implications for myriad fields.