Hydrogel Microparticle-Templated Anti-Solvent Crystallization of Small-Molecule Drugs

In-situ sequential crystallization of fenofibrate and tristearin - Understanding the distribution of API in particles and stability of solid lipid microparticles from the perspective of crystallization

In-situ API crystallization in carrier matrices has attracted extensive attention in recent years for its advantages over traditional preparation processes. However, due to the lack of systemic research on molecular self-assembly behaviors, the products obtained by in-situ crystallization suffer from the problems of polymorphic transformation and drug expulsion during storage, limiting its industrial application. This paper investigates the in-situ sequential crystallization behavior of tristearin (SSS) and fenofibrate (FEN), utilizing SSS as the carrier and FEN as the API. It was found that the behavior of mixed crystallization significantly differs from single-component crystallization, including direct formation of stable form of SSS and the rapid crystallization of FEN. During the crystallization process, the melting FEN promotes the movement of SSS molecules, while the sliding of SSS lamellae, in turn, provides a mechanical stimulus to enhance the nucleation of FEN. Based on the observed synergistic crystallization behavior, the distribution and stability of the API within FEN solid lipid microparticles (SLMs) during storage were evaluated, while also examining the stability variations in SLMs formulated at different cooling rates and drug loading concentrations. The findings indicate that the initial nucleated FEN results in a decrease in the surrounding molten FEN and the irregularity of the SSS lamellas, thereby preventing the remaining molten FEN from achieving complete crystallization within a brief period. Due to the compatibility between FEN and SSS, some SSS may blend with the molten FEN, potentially resulting in further crystallization during storage and consequently increasing the risk of drug expulsion.

Pathophysiology to advanced intra-articular drug delivery strategies: Unravelling rheumatoid arthritis

Rheumatoid arthritis (RA) is one of the most prevalent life-long autoimmune diseases with an unknown genesis. It primarily causes chronic inflammation, pain, and synovial joint-associated cartilage and bone degradation. Unfortunately, limited information is available regarding the etiology and pathogenesis of this chronic joint disorder. In the last few decades, an improved understanding of RA pathophysiology about key immune cells, antibodies, and cytokines has inspired the development of several anti-rheumatic drugs and biopharmaceuticals to act on RA-affected joints. However, life-long frequent systemic high doses of commercially available drugs are currently a limiting factor in the efficient management of RA. To address this issue, various single and double-barrier intra-articular drug delivery systems (IA-DDSs) such as nanocarriers, microparticles, hydrogels, and particles-hybrid hydrogel composite have been developed which can exclusively target the RA-affected joint cavity and release the precisely controlled therapeutic drug concentration for prolonged time whilst avoiding the systemic toxicity. This review provides a comprehensive overview of the pathogenesis of RA and discusses the rational design and development of biomaterials-based novel IA-DDs, ranging from conventional to advanced systems, for improved treatment of RA. Therefore, this review aims to unravel the pathophysiology of rheumatoid arthritis and explore cutting-edge IA-DD strategies exploiting biomaterials. It offers researchers a consolidated and up-to-date resource platform to analyze existing knowledge, identify research gaps, and contribute to the scientific literature.

Templated Reactive Crystallization of Active Pharmaceutical Ingredient in Hydrogel Microparticles Enabling Robust Drug Product Processing

Commercialization of most promising active pharmaceutical ingredients (APIs) is impeded either by poor bioavailability or challenging physical properties leading to costly manufacture. Bioavailability of ionizable hydrophobic APIs can be enhanced by its conversion to salt form. While salt form of the API presents higher solution concentration than the non-ionized form, poor physical properties resulting from particle anisotropy or non-ideal morphology (needles) and particle size distribution not meeting dissolution rate targets can still inhibit its commercial translation. In this regard, API physical properties can be improved through addition of non-active components (excipients or carriers) during API manufacture. In this work, a facile method to perform reactive crystallization of an API salt in presence of the microporous environment of a hydrogel microparticle is presented. Specifically, the reaction between acidic antiretroviral API, raltegravir and base potassium hydroxide is performed in the presence of polyethylene glycol diacrylamide hydrogel microparticles. In this bottom-up approach, the spherical template hydrogel microparticles for the reaction lead to monodisperse composites loaded with inherently micronized raltegravir-potassium crystals, thus improving API physical properties without hampering bioavailability. Overall, this technique provides a novel approach to reactive crystallization while maintaining the API polymorph and crystallinity.

Self-assembling nanoarchitectonics of size-controllable celastrol nanoparticles for efficient cancer chemotherapy with reduced systemic toxicity

Celastrol, extracted from Tripterygium wilfordii Hook F, is one of the most promising natural extract for cancer treatment. Nevertheless, insufficient tumor retention and severe systemic toxicity still hinder its application. Herein, we report for the first time that Celastrol can directly self-assemble into size-controllable nanoparticles through the anti-solvent method by using different good solvent or by the variation of Celastrol concentrations. In vitro anti-cancer experiment revealed that the as-prepared nanoparticles can kill MCF-7 cells more effectively. Moreover, the nanoparticles can efficiently accumulate in tumors of the tumor bearing mice after tail vein injection. Under the administration of lethal dosage of Celastrol, the tumors are greatly suppressed and the mice maintain the activity. These results demonstrate that anti-solvent method may be a promising strategy to fabricate Celastrol nano-drugs with controllable size and less systemic toxicity for further clinical cancer treatment.

Improving ocular bioavailability of hydrophilic drugs through dynamic covalent complexation

The clinical benefits of diquafosol tetrasodium (DQS), a hydrophilic P2Y2 receptor agonist for dry eye, have been hindered by a demanding dosing regimen. Nevertheless, it is challenging to achieve sustained release of DQS with conventional drug delivery vehicles which are mainly designed for hydrophobic small molecule drugs. To address this, we developed an affinity hydrogel for DQS by taking advantage of borate-mediated dynamic covalent complexation between DQS and hydroxypropyl guar. The resultant formulation (3% DQS Gel) was characterized by sustained release, low corneal permeation, and extended ocular retention, which were desirable attributes for ocular surface drug delivery. Both in vitro and in vivo studies had been carried out to verify the biocompatibility of 3% DQS Gel. Using corneal fluorescein staining, the Schirmer's test, PAS staining, quantitative PCR and immunohistological analyses as outcome measures, the superior therapeutic effects of 3% DQS Gel over PBS, the hydrogel vehicle and free DQS were demonstrated in a mouse dry eye model. Our DQS delivery strategy reported herein is readily applicable to other hydrophilic small molecule drugs with cis-diol moieties, thus providing a general solution to improve clinical outcomes of numerous diseases.