Exploring the systemic delivery of a poorly water-soluble model drug to the retina using PLGA nanoparticles

Research Progress on Immunomodulatory Effects of Poly (Lactic-co- Glycolic Acid) Nanoparticles Loaded with Traditional Chinese Medicine Monomers

Immunomodulatory mechanisms are indispensable and key factors in maintaining the balance of the environment in humans. When the immune function of the immune system is impaired, autoimmune diseases occur. Excessive body fatigue, natural aging of the human body, malnutrition, genetic factors and other reasons cause low immune function, due to which the body is prone to being infected by bacteria or cancer. Clinically, the existing therapeutic drugs still have problems such as high toxicity, long treatment cycle, drug resistance and high price, so we still need to explore and develop a high efficiency and low toxicity drug. Poly(lactic-co-glycolic acid) (PLGA) refers to a nontoxic polymer compound that exhibits excellent biocompatibility. Traditional Chinese medicine (TCM) monomers come from natural plants, and have the characteristics of high efficiency and low toxicity. Applying PLGA to TCM monomers can make up for the defects of traditional dosage forms, improve bioavailability, reduce the frequency and dosage of drug use, and reduce toxicity and side effects, thus having the characteristics of sustained release and targeting. Accordingly, PLGA nanoparticles loaded with TCM monomers have been the focus of development. The previous research on drug loading advantages, preparation methods, and immune regulation of TCM PLGA nanoparticles is summarized in the following sections.

Recent Updates on Nanocarriers for Drug Delivery in Posterior Segment Diseases with Emphasis on Diabetic Retinopathy

In recent years, various conventional formulations have been used for the treatment and/or management of ocular medical conditions. Diabetic retinopathy, a microvascular disease of the retina, remains the leading cause of visual disability in patients with diabetes. Currently, for treating diabetic retinopathy, only intraocular, intravitreal, periocular injections, and laser photocoagulation are widely used. Frequent administration of these drugs by injections may lead to serious complications, including retinal detachment and endophthalmitis. Although conventional ophthalmic formulations like eye drops, ointments, and suspensions are available globally, these formulations fail to achieve optimum drug therapeutic profile due to immediate nasolacrimal drainage, rapid tearing, and systemic tearing toxicity of the drugs. To achieve better therapeutic outcomes with prolonged release of the therapeutic agents, nano-drug delivery materials have been investigated. These nanocarriers include nanoparticles, solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), dendrimers, nanofibers, in-situ gel, vesicular carriers, niosomes, and mucoadhesive systems, among others. The nanocarriers carry the potential benefits of site-specific delivery and controlled and sustained drug release profile. In the present article, various nanomaterials explored for treating diabetic retinopathy are reviewed.

Fluorescently Labeled PLGA Nanoparticles for Visualization In Vitro and In Vivo: The Importance of Dye Properties

Fluorescently labeled nanoparticles are widely used for evaluating their distribution in the biological environment. However, dye leakage can lead to misinterpretations of the nanoparticles' biodistribution. To better understand the interactions of dyes and nanoparticles and their biological environment, we explored PLGA nanoparticles labeled with four widely used dyes encapsulated (coumarin 6, rhodamine 123, DiI) or bound covalently to the polymer (Cy5.5.). The DiI label was stable in both aqueous and lipophilic environments, whereas the quick release of coumarin 6 was observed in model media containing albumin (42%) or liposomes (62%), which could be explained by the different affinity of these dyes to the polymer and lipophilic structures and which we also confirmed by computational modeling (log PDPPC/PLGA: DiI-2.3, Cou6-0.7). The importance of these factors was demonstrated by in vivo neuroimaging (ICON) of the rat retina using double-labeled Cy5.5/Cou6-nanoparticles: encapsulated Cou6 quickly leaked into the tissue, whereas the stably bound Cy.5.5 label remained associated with the vessels. This observation is a good example of the possible misinterpretation of imaging results because the coumarin 6 distribution creates the impression that nanoparticles effectively crossed the blood-retina barrier, whereas in fact no signal from the core material was found beyond the blood vessels.