Effects of drying methods on the preparation of dexamethasone-loaded chitosan microspheres

Locally released dexamethasone and its effects on osteogenic activity at implant-tissue interface

The osseointegration of titanium implants within the host tissue holds crucial importance. The introduction of functional coatings at tissue-implant interface enhances the bioactivity of titanium implants, improves their therapeutic outcomes, and enhances the effectiveness of treatments. In this study, we focused on enhancing the bioactivity of titanium-based implant materials by coating the titanium surfaces with chitosan microspheres, which are loaded with osseointegration-promoting agent dexamethasone (DEX). Initially, chitosan microspheres were successfully produced, followed by DEX loading through diffusion, resulting in a drug loading efficiency of around 50.2 (wt %). The subsequent drug release profile displayed a 24-hour duration, releasing approximately 32.6 (wt %) of the loaded DEX. In cell proliferation assays using human osteosarcoma (SAOS-2) cells, Ti surfaces coated with DEX-loaded chitosan microspheres initially exhibited lower cell numbers compared with DEX-free ones. This observation was attributed to transient osteogenic differentiation effects of DEX, since a notable increase in cell proliferation was observed on the 7th day. Von Kossa staining revealed mineralization beginning on the 14th day, particularly evident in DEX-loaded samples. Moreover, alkaline phosphatase (ALP) activity displayed a pattern of initial increase and subsequent decrease, with DEX release from chitosan microspheres showing a clear influence on the osteogenic differentiation, especially on the 7th day. These findings align with literature, highlighting DEX's potential to enhance osteogenic differentiation and cellular behavior on chitosan microsphere-coated titanium surfaces. This study emphasizes the promising implications for functionalizing surfaces of implant materials with DEX-loaded chitosan microspheres to improve their biocompatibility and bioactivity.

Functional microspheres for tissue regeneration

As a new type of injectable biomaterials, functional microspheres have attracted increasing attention in tissue regeneration because they possess some advantageous properties compared to other biomaterials, including hydrogels. A variety of bio-inspired microspheres with unique structures and properties have been developed as cellular carriers and drug delivery vehicles in recent years. In this review, we provide a comprehensive summary of the progress of functional and biodegradable microspheres that have been used for tissue regeneration over the last two decades. First, we briefly introduce the biomaterials and general methods for microsphere fabrication. Next, we focus on the newly developed technologies for preparing functional microspheres, including macroporous microspheres, nanofibrous microspheres, hollow microspheres, core-shell structured microspheres, and surface-modified functional microspheres. After that, we discuss the application of functional microspheres for tissue regeneration, specifically for bone, cartilage, dental, neural, cardiac, and skin tissue regeneration. Last, we present our perspectives and future directions of functional microspheres as injectable carriers for the future advancement of tissue regeneration.

Dexamethasone: Insights into Pharmacological Aspects, Therapeutic Mechanisms, and Delivery Systems

Dexamethasone (DEX) has been widely used to treat a variety of diseases, including autoimmune diseases, allergies, ocular disorders, cancer, and, more recently, COVID-19. However, DEX usage is often restricted in the clinic due to its poor water solubility. When administered through a systemic route, it can elicit severe side effects, such as hypertension, peptic ulcers, hyperglycemia, and hydro-electrolytic disorders. There is currently much interest in developing efficient DEX-loaded nanoformulations that ameliorate adverse disease effects inhibiting advancements in scientific research. Various nanoparticles have been developed to selectively deliver drugs without destroying healthy cells or organs in recent years. In the present review, we have summarized some of the most attractive applications of DEX-loaded delivery systems, including liposomes, polymers, hydrogels, nanofibers, silica, calcium phosphate, and hydroxyapatite. This review provides our readers with a broad spectrum of nanomedicine approaches to deliver DEX safely.

Influence of drying processes on the structures, morphology and in vitro release profiles of risperidone-loaded PLGA microspheres

The purpose of this study was to investigate the influences of drying methods on the risperidone (RIS) release profiles of RIS-loaded PLGA microspheres. These microspheres were fabricated with an O/W emulsion solvent evaporation method. The wet microspheres were dried with freeze drying and vacuum drying methods. The microspheres were mono-dispersed spheres with an average diameter of 100 μm. Studies found that drying methods had great influence on the porosity, morphology, and release profiles of RIS-loaded PLGA microspheres. Specifically, the freeze-dried microspheres had higher porosity (78.46 ± 1.64%) than those vacuum-dried ones (52.45 ± 2.68%), and they showed higher RIS release rates (p < 0.05). In the accelerated release tests (45 °C), these microspheres dried under the pressures of 700 mmHg and 200 mmHg gave faster release rates than those ones dried under the pressure of 450 mmHg. Importantly, the accelerated release test (45 °C) had a high correlation with the real-time test (37 °C) (R² > 0.99). These studies exhibited a significance in the precise preparation of RIS-loaded PLGA microspheres.

Formulation, optimization, and pharmacodynamic evaluation of chitosan/phospholipid/β-cyclodextrin microspheres

Cholinergic neurotransmission loss is the main cause of cognitive impairment in patients with Alzheimer's disease. Phospholipids (PLs) play an essential role in memory and learning abilities. Moreover, PLs act as a source of choline in acetylcholine synthesis. This study aimed to prepare and optimize the formulation of chitosan/phospholipid/β-cyclodextrin (CTS/PL/β-CD) microspheres that can improve cognitive impairment. The CTS/PL/β-CD microspheres were prepared by spray drying, and optimized with an orthogonal design. These microspheres were also characterized in terms of morphology, structure, thermostability, drug loading, and encapsulation efficiency. The spatial learning and memory of rats were evaluated using the Morris water maze test, and the neuroprotective effects of the CTS/PL/β-CD micro-spheres were investigated by immunohistochemistry. Scanning electron microscopic images showed that the CTS/PL/β-CD microspheres were spherical with slightly wrinkled surfaces. Fourier transform infrared spectroscopy and differential scanning calorimetry proved that PLs formed hydrogen bonds with the amide group of CTS and the hydroxyl group of β-CD. The learning and memory abilities of rats in the treated group significantly improved compared with those in the model group. Immunohistochemical analysis revealed that treatment with the CTS/PL/β-CD microspheres attenuated the expression of protein kinase C-δ and inhibited the activation of microglias. These results suggest that the optimized microspheres have the potential to be used in the treatment of Alzheimer's disease.