Control of Drug Release from Microparticles by Tuning Their Crystalline Textures: A Structure–Activity Study

Abstract

Predicting drug release profiles from polymer microparticles has proven challenging due to the numerous environmental and chemical factors that affect the device and influence the rate of drug release. By measuring the various polymer properties that can influence drug release, a predictive approach can be used to select polymers with specific properties that will lead to the desired release profile for the application. To illustrate this, a library of tyrosol-derived poly(ester-arylate)s, poly(amide)s, and poly(carbonate)s were used to evaluate the effects of physical (crystallinity, water accessibility, thermal, and hydrophobicity) and chemical (polymer−drug interactions) polymer properties on the release of a highly crystalline drug dexamethasone, which was loaded at a high weight percent (wt %) in microparticles. Nuclear magnetic resonance (NMR) experiments showed that the polymer and drug were not chemically interacting and instead exist as a physical mixture even after exposure to physiological conditions. Polymer crystallinity data revealed that crystallite size was strongly correlated with faster drug release, suggesting that larger crystallites reduce the tortuosity for dexamethasone to diffuse out of the particle matrix. This correlation observed in particles with and without the drug was reproduced with bulk polymers, indicating that crystallinity data from bulk polymers can be used to predict release profiles without having to prepare drug-loaded particles. Consistent with the crystallinity data, particle pore sizes of representative formulations showed that particles with larger pores resulted in faster dexamethasone release. Interestingly, thermal properties (glass transition temperature and melting temperature), polymer hydrophobicity, and molecular weight retention at the end of the 119-day release study did not show any correlation with drug release.

Recent progress in nanomedicines for imaging and therapy of brain tumors

“…11,12 Importantly, the remarkable advantages in blood–brain barrier crossing nanotechnology make brain tumor imaging and therapy a great opportunity. 11,14…”

“…11,12 Importantly, the remarkable advantages in blood-brain barrier crossing nanotechnology make brain tumor imaging and therapy a great opportunity. 11,14 Brain tumors are life-threatening diseases, bearing a low survival rate for patients. 15,16 According to the World Health Organization (WHO) classification in the year 2021 (Fig.…”

Encapsulated Transition Metal Catalysts Enable Long-term Stability in Frontal Polymerization Resins

“…Alternatively, we propose that latency in FROMP resins can be achieved via a localized separation between monomer and active catalyst that can be removed upon exposure to an external stimulusa technique ubiquitous in biological systems. , An established way to delay contact between reactive pairs is the encapsulation of molecular cargo in the form of polymer microparticles (PMPs). This well-studied method has been applied to the controlled release of drug molecules, , catalyst species, − and polymerization initiators. − Pojman et al demonstrated that microencapsulation of organic peroxide initiators increases the storage life of free-radical acrylate FP . Extended storage times (>1 day) resulted in significant decreases in the mechanical properties of the polymer products and SP still occurred within a two month period.…”