Optimization of PLG microspheres for tailored drug release

On the estimation of the size of a droplet emerging from a pore opening into a crossflow field

The problem of terminating a droplet at the surface of a membrane in a crossflow field is an important topic in the context of controlled emulsification of fluids for use in pharmaceutical and other industries. Some of these industries struggle to produce emulsions of uniform sizes for their products requiring higher levels of precision. In this work, we comprehensively investigated one such technique in which droplets were produced via membrane openings and were terminated via a crossflow field. Conditions of permeation and termination were identified. A model was developed to estimate the size of the emerging droplets from information about the interfacial properties, geometry, and operating conditions (i.e., pressure and crossflow velocity). Three forces, including capillary pressure, interfacial tension, and drag forces, were identified that account for a developed torque balance, which was then used to determine the onset of breakup of an emerging droplet. A comprehensive computational fluid dynamics (CFD) analysis has been conducted to highlight the physics involved in the process and also to provide scenarios for comparison exercises. The effects of crossflow velocity, applied pressure, and viscosity contrasts have been studied. It has been determined that the emerging droplet experiences deformation along the crossflow field because of the hydrodynamic drag. The receding portion of the contact line at the surface of the membrane wraps around the pore opening, generating an interfacial tension force that produces an opposing torque due to the crossflow drag and capillary pressure. Using this phenomenon, a framework for estimating the size of the droplet upon breakup is established. Comparisons with the results obtained from the CFD analysis under different conditions show very good agreement, which builds confidence in the modeling approach.

Formulation optimization and in vitro characterization of granisetron-loaded polylactic-co-glycolic acid microspheres prepared by a dropping-in-liquid emulsification technique

PURPOSE

Traditional dosage forms of granisetron (GRN) decrease patient compliance associated with repeated drug administration because of the short half-life of the drug.

METHODS

In this study, novel GRN-loaded polylactic-co-glycolic acid (PLGA) sustained release microspheres were prepared for the first time via a dropping-in-liquid emulsification technique. The effect of various factors, such as pH of the outer phase, Tween80, polyvinyl alcohol (PVA) concentrations, and hardening process, on the encapsulation efficiency (EE), drug loading (DL), and particle size of microspheres were extensively studied. The physicochemical properties, including drug release, surface morphology, crystallinity, thermal changes, and molecular interactions, were also studied.

RESULTS

GRN has a pH-dependent solubility and showed a remarkably high solubility under an acidic condition. The EE of the alkaline medium (pH 8) was higher than that of the acidic medium (pH 4.0). EE and DL decreased in the presence of Tween80 in the outer phase, whereas EE significantly increased during hardening. The particle size of microspheres was not affected by PVA and Tween80 concentrations, but it was influenced by PVA volume and hardening. X-ray diffraction and differential scanning calorimetry results showed that the physical state of the drug changed from a crystalline form to an amorphous form, thereby confirming that the drug was encapsulated into the PLGA matrix. Fourier transform-infrared spectroscopy confirmed that some molecular interactions occurred between the drug and the polymer. GRN-loaded PLGA microspheres showed sustained release profiles of over 90% on week 3.

CONCLUSION

GRN-loaded PLGA microspheres with sustained release were successfully prepared, and they exhibited a relatively high EE without Tween 80 as an emulsifier and with hardening process.

Kinetic Release Studies of Antibiotic Patches for Local Transdermal Delivery

This study investigates the usage of electrohydrodynamic (EHD)-3D printing for the fabrication of bacterial cellulose (BC)/polycaprolactone (PCL) patches loaded with different antibiotics (amoxicillin (AMX), ampicillin (AMP), and kanamycin (KAN)) for transdermal delivery. The composite patches demonstrated facilitated drug loading and encapsulation efficiency of drugs along with extended drug release profiles. Release curves were also subjected to model fitting, and it was found that drug release was optimally adapted to the Higuchi square root model for each drug. They performed a time-dependent and diffusion-controlled release from the patches and followed Fick’s diffusion law by the Korsmeyer–Peppas energy law equation. Moreover, produced patches demonstrated excellent antimicrobial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) strains, so they could be helpful in the treatment of chronic infectious lesions during wound closures. As different tests have confirmed, various types of antibiotics could be loaded and successfully released regardless of their types from produced BC/PCL patches. This study could breathe life into the production of antibiotic patches for local transdermal applications in wound dressing studies and improve the quality of life of patients.

Production of monodisperse polyurea microcapsules using microfluidics

Methods to make microcapsules - used in a broad range of healthcare and energy applications - currently suffer from poor size control, limiting the establishment of size/property relationships. Here, we use microfluidics to produce monodisperse polyurea microcapsules (PUMC) with a limonene core. Using varied flow rates and a commercial glass chip, we produce capsules with mean diameters of 27, 30, 32, 34, and 35 µm, achieving narrow capsule size distributions of ±2 µm for each size. We describe an automated method of sizing droplets as they are produced using video recording and custom Python code. The sustainable generation of such size-controlled PUMCs, potential replacements for commercial encapsulated systems, will allow new insights into the effect of particle size on performance.

Mathematical modeling of drug delivery from autocatalytically degradable PLGA microspheres--a review

PLGA microspheres are widely studied for controlled release drug delivery applications, and many models have been proposed to describe PLGA degradation and erosion and drug release from the bulk polymer. Autocatalysis is known to have a complex role in the dynamics of PLGA erosion and drug transport and can lead to size-dependent heterogeneities in otherwise uniformly bulk-eroding polymer microspheres. The aim of this review is to highlight mechanistic, mathematical models for drug release from PLGA microspheres that specifically address interactions between phenomena generally attributed to autocatalytic hydrolysis and mass transfer limitation effects. Predictions of drug release profiles by mechanistic models are useful for understanding mechanisms and designing drug release particles.

Polymeric Microspheres for Medical Applications

Synthetic polymeric microspheres find application in a wide range of medical applications. Among other applications, microspheres are being used as bulking agents, embolic- or drug-delivery particles. The exact composition of the spheres varies with the application and therefore a large array of materials has been used to produce microspheres. In this review, the relation between microsphere synthesis and application is discussed for a number of microspheres that are used for different treatment strategies.