Microparticles, microspheres, and microcapsules are widely used constituents of multiparticulate drug delivery systems, offering both therapeutic and technological advantages. Microparticles are generally in the 1–1000 µm size range, serve as multiunit drug delivery systems with well-defined physiological and pharmacokinetic benefits in order to improve the effectiveness, tolerability, and patient compliance. This paper reviews their evolution, significance, and formulation factors (excipients and procedures), as well as their most important practical applications (inhaled insulin, liposomal preparations). The article presents the most important structures of microparticles (microspheres, microcapsules, coated pellets, etc.), interpreted with microscopic images too. The most significant production processes (spray drying, extrusion, coacervation, freeze-drying, microfluidics), the drug release mechanisms, and the commonly used excipients, the characterization, and the novel drug delivery systems (microbubbles, microsponges), as well as the preparations used in therapy are discussed in detail.

To develop proper drug formulations and to optimize the delivery of their active ingredients through the dermal barrier, the Franz diffusion cell system is the most widely used in vitro/ex vivo technique. However, different providers and manufacturers make various types of this equipment (horizontal, vertical, static, flow-through, smaller and larger chambers, etc.) with high variability and not fully comparable and consistent data. Furthermore, a high amount of test drug formulations and large size of diffusion skin surface and membranes are important requirements for the application of these methods. The aim of our study was to develop a novel Microfluidic Diffusion Chamber device and compare it with the traditional techniques. Here the design, fabrication, and a pilot testing of a microfluidic skin-on-a chip device are described. Based on this chip, further developments can also be implemented for industrial purposes to assist the characterization and optimization of drug formulations, dermal pharmacokinetics, and pharmacodynamic studies. The advantages of our device, beside the low costs, are the small drug and skin consumption, low sample volumes, dynamic arrangement with continuous flow mimicking the dermal circulation, as well as rapid and reproducible results.

The efficacy of transdermal absorption of drugs and the irritation or corrosion potential of topically applied formulations are important areas of investigation in pharmaceutical, military and cosmetic research. The aim of the present experiments is to test the role of P-glycoprotein in dermal drug delivery in various ex vivo and in vitro platforms, including a novel microchip technology developed by Pázmány Péter Catholic University. A further question is whether the freezing of excised skin and age have any influence on P-glycoprotein-mediated dermal drug absorption. Two P-glycoprotein substrate model drugs (quinidine and erythromycin) were investigated via topical administration in diffusion cells, a skin-on-a-chip device and transdermal microdialysis in rat skin. The transdermal absorption of both model drugs was reduced by P-glycoprotein inhibition, and both aging and freezing increased the permeability of the tissues. Based on our findings, it is concluded that the process of freezing leads to reduced function of efflux transporters, and increases the porosity of skin. P-glycoprotein has an absorptive orientation in the skin, and topical inhibitors can modify its action. The defensive role of the skin seems to be diminished in aged individuals, partly due to reduced thickness of the dermis. The novel microfluidic microchip seems to be an appropriate tool to investigate dermal drug delivery.

Organ-on-a-chip technologies show exponential growth driven by the need to reduce the number of experimental animals and develop physiologically relevant human models for testing drugs. In vitro, microfluidic devices should be carefully designed and fabricated to provide reliable tools for modeling physiological or pathological conditions and assessing, for example, drug delivery through biological barriers. The aim of the current study was to optimize the utilization of three existing skin-on-a-chip microfluidic diffusion chambers with various designs. For this, different perfusion flow rates were compared using cellulose acetate membrane, polyester membrane, excised rat skin, and acellular alginate scaffold in the chips. These diffusion platforms were integrated into a single-channel microfluidic diffusion chamber, a multi-channel chamber, and the LiveBox2 system. The experimental results revealed that the 40 µL/min flow rate resulted in the highest diffusion of the hydrophilic model formulation (2% caffeine cream) in each system. The single-channel setup was used for further analysis by computational fluid dynamics simulation. The visualization of shear stress and fluid velocity within the microchannel and the presentation of caffeine progression with the perfusion fluid were consistent with the measured data. These findings contribute to the development and effective application of microfluidic systems for penetration testing.

Background/Objectives: To improve the therapeutic efficacy of albendazole (ABZ) for ileocolonic diseases, its low solubility at higher pH levels should be enhanced. Organic acids have been widely used as pH modifiers to improve the solubility of weakly basic drugs. To achieve an adequate effect of the acidic microenvironmental pH during the drug release, pH modifiers should not leach out from the formulation. In the present work, we aimed to demonstrate that 100% tartaric acid pellets (TAP) can be used as pH-modifier cores, providing an acidic microenvironmental pH to enhance the solubility of albendazole at a higher pH. Methods: This study develops multilayer-coated pellets using TAP as starter cores in a bottom-spray-configured fluidized bed apparatus. The drug-layered TAP were coated with time-dependent and pH-dependent layers. Results: The release of ABZ from tartaric acid-based coated pellets was enhanced compared to that from pellets with the same layering structure but with an inert core of sugar or microcrystalline cellulose (MCC). In vitro experiments showed that tartaric acid remained in the pellet core during the dissolution test at a pH 6.8 medium, which resulted in an enhanced release of albendazole at a higher pH. The application of a combination of time-dependent and pH-dependent polymers aimed not only to prevent the release of albendazole at lower pH levels but also to protect TAP from premature release from the formulation. Conclusions: The application of 100% ready-to-use tartaric acid pellets (TAP) with the applied combination of coatings enhanced the solubility of the weakly basic drug albendazole at higher intestinal pH.

Giardia duodenalis is a flagellated protozoan pathogen causing parasitic enteric disease outbreaks worldwide. Among detection methods, loop-mediated isothermal amplification (LAMP) has high selectivity and sensitivity, and the detection time is lower than that of conventional molecular methods. In this study, three published Giardia LAMP primer sets were tested and adapted to touchdown LAMP conditions. The measurement time, the volume of reagents, the effect of the denaturation step, different kinds of polymerases, and the presence or absence of betaine on the reaction were tested and evaluated. Based on the results of this study, the 66–60 °C range touchdown LAMP with the use of betaine, 90 °C denaturation step, Bst 2.0 WarmStart^® DNA Polymerase, and the primer set of Momoda et al. were the optimal conditions. We increased the analytical sensitivity of the LAMP reaction to 7.8- and 8-fold higher than the previously published methods for G. duodenalis assemblages A and B, with detection limits of 20 and 19.5 fg/assay, respectively, instead of 156 fg/assay. The detection time was less than 49 min for G. duodenalis assemblage A and less than 35 min for assemblage B, compared to the previously published 60 min. Our optimized LAMP protocol can be directly applied to improve Giardia LAMP tests in routine testing laboratories, could be implemented in standard diagnostic or environmental monitoring workflows, and can be used for the development of Giardia LAMP point-of-care devices or high-throughput systems.