A Comparison of Chitosan, Mesoporous Silica and Poly(lactic-co-glycolic) Acid Nanocarriers for Optimising Intestinal Uptake of Oral Protein Therapeutics

Biomedical applications of PLGA nanoparticles in nanomedicine: advances in drug delivery systems and cancer therapy

INTRODUCTION

During the last decades, the ever-increasing proportion of patients with cancer has been led to serious concerns worldwide. Therefore, the development and use of novel pharmaceuticals, like nanoparticles (NPs)-based drug delivery systems (DDSs), can be potentially effective in cancer therapy.

AREA COVERED

Poly lactic-co-glycolic acid (PLGA) NPs, as a kind of bioavailable, biocompatible, and biodegradable polymers, have approved by the Food and Drug Administration (FDA) for some biomedical and pharmaceutical applications. PLGA is comprised of lactic acid (LA) and glycolic acid (GA) and their ratio could be controlled during various syntheses and preparation approaches. LA/GA ratio determines the stability and degradation time of PLGA; lower content of GA results in fast degradation. There are several approaches for preparing PLGA NPs that can affect their various aspects, such as size, solubility, stability, drug loading, pharmacokinetics, and pharmacodynamics, and so on.

EXPERT OPINION

These NPs have indicated the controlled and sustained drug release in the cancer site and can use in passive and active (via surface modification) DDSs. This review aims to provide an overview of PLGA NPs, their preparation approach and physicochemical aspects, drug release mechanism and the cellular fate, DDSs for efficient cancer therapy, and status in the pharmaceutical industry and nanomedicine.

A membrane-free microfluidic approach to mucus permeation for efficient differentiation of mucoadhesive and mucopermeating nanoparticulate systems

The gastrointestinal mucus barrier is a widely overlooked yet essential component of the intestinal epithelium, responsible for the body's protection against harmful pathogens and particulates. This, coupled with the increasing utilisation of biological molecules as therapeutics (e.g. monoclonal antibodies, RNA vaccines and synthetic proteins) and nanoparticle formulations for drug delivery, necessitates that we consider the additional absorption barrier that the mucus layer may pose. It is imperative that in vitro permeability methods can accurately model this barrier in addition to standardised cellular testing. In this study, a mucus-on-a-chip (MOAC) microfluidic device was engineered and developed to quantify the permeation kinetics of nanoparticles through a biorelevant synthetic mucus layer. Three equivalently sized nanoparticle systems, formulated from chitosan (CSNP), mesoporous silica (MSNP) and poly (lactic-co-glycolic) acid (PLGA-NP) were prepared to encompass various surface chemistries and nanostructures and were assessed for their mucopermeation within the MOAC. Utilising this device, the mucoadhesive behaviour of chitosan nanoparticles was clearly visualised, a phenomenon not often observed via standard permeation models. In contrast, MSNP and PLGA-NP displayed mucopermeation, with significant differences in permeation pattern due to specific mucus-nanoparticle binding. Further optimisation of the MOAC to include a more biorelevant mucus mimic resulted in 5.5-fold hindered PLGA-NP permeation compared to a mucin solution. Furthermore, tracking of PLGA-NP at a single nanoparticle resolution revealed rank-order correlations between particle diffusivity and MOAC permeation. This device, including utilisation of biosimilar mucus, provides a unique ability to quantify both mucoadhesion and mucopenetration of nano-formulations and elucidate mucus binding interactions on a microscopic scale.

Optimisation of a High-Throughput Model for Mucus Permeation and Nanoparticle Discrimination Using Biosimilar Mucus

High-throughput permeation models are essential in drug development for timely screening of new drug and formulation candidates. Nevertheless, many current permeability assays fail to account for the presence of the gastrointestinal mucus layer. In this study, an optimised high-throughput mucus permeation model was developed employing a highly biorelevant mucus mimic. While mucus permeation is primarily conducted in a simple mucin solution, the complex chemistry, nanostructure and rheology of mucus is more accurately modelled by a synthetic biosimilar mucus (BSM) employing additional protein, lipid and rheology-modifying polymer components. Utilising BSM, equivalent permeation of various molecular weight fluorescein isothiocyanate-dextrans were observed, compared with native porcine jejunal mucus, confirming replication of the natural mucus permeation barrier. Furthermore, utilising synthetic BSM facilitated the analysis of free protein permeation which could not be quantified in native mucus due to concurrent proteolytic degradation. Additionally, BSM could differentiate between the permeation of poly (lactic-co-glycolic) acid nanoparticles (PLGA-NP) with varying surface chemistries (cationic, anionic and PEGylated), PEG coating density and size, which could not be achieved by a 5% mucin solution. This work confirms the importance of utilising highly biorelevant mucus mimics in permeation studies, and further development will provide an optimal method for high-throughput mucus permeation analysis.

Influence of Critical Parameters on Cytotoxicity Induced by Mesoporous Silica Nanoparticles

Mesoporous Silica Nanoparticles (MSNs) have received increasing attention in biomedical applications due to their tuneable pore size, surface area, size, surface chemistry, and thermal stability. The biocompatibility of MSNs, although generally believed to be satisfactory, is unclear. Physicochemical properties of MSNs, such as diameter size, morphology, and surface charge, control their biological interactions and toxicity. Experimental conditions also play an essential role in influencing toxicological results. Therefore, the present study includes studies from the last five years to statistically analyse the effect of various physicochemical features on MSN-induced in-vitro cytotoxicity profiles. Due to non-normally distributed data and the presence of outliers, a Kruskal–Wallis H test was conducted on different physicochemical characteristics, including diameter sizes, zeta-potential measurements, and functionalisation of MSNs, based on the viability results, and statistical differences were obtained. Subsequently, pairwise comparisons were performed using Dunn’s procedure with a Bonferroni correction for multiple comparisons. Other experimental parameters, such as type of cell line used, cell viability measurement assay, and incubation time, were also explored and analysed for statistically significant results.

Encapsulation of bioactive peptides: a strategy to improve the stability, protect the nutraceutical bioactivity and support their food applications

In recent decades, bioactive peptides have become an emerging field of interest in the scientific community as well as the food, pharmaceutical, and cosmetics industries. A growing body of research indicates that consumption of bioactive peptides may play a vital role in health through their broad spectrum of bioactivity such as antioxidant, antihypertensive, antimicrobial, anti-inflammatory, immunomodulatory, and anti-proliferative activities. In addition, bioactive peptides can be used as food preservatives due to their antimicrobial and antioxidant activities. However, some factors limit their nutraceutical and commercial applications, including easy chemical degradation (e.g., pH, enzymatic), food matrix interaction, low water-solubility, hygroscopicity, and potential bitter taste. Bearing that in mind, the encapsulation of bioactive peptides in different materials can help overcome these challenges. Studies have demonstrated that encapsulation of bioactive peptides increases their bioactivity, improves their stability, sensory properties, increases solubility, and decreases hygroscopicity. However, there is limited scientific evidence about the bioavailability and food matrix interactions of encapsulated peptides. Besides, the diverse colloidal systems used to encapsulate bioactive peptides have shown stability and good encapsulation efficiency. This review provides an overview of current advances in the encapsulation of bioactive peptides, considering the technology, developments, and innovations in the last lustrum.

Chitosan nanoparticles facilitate improved intestinal permeation and oral pharmacokinetics of the mast cell stabiliser cromoglycate

Cromoglycate is a mast cell stabiliser typically administered via inhalation or intranasally for the treatment of allergy-based respiratory issues. Oral dosing of cromoglycate remains challenging due to its high solubility but low permeability across epithelial membranes in the gastrointestinal tract: effective formulation strategies are clearly needed. Here, we investigate and preclinically develop chitosan-cromoglycate complexes and associated nano/microparticle formulations with muco-adhesive and permeation enhancing capabilities to overcome the biopharmaceutical challenges for oral dosing.The synthesized complexes were optimized with respect to chitosan grade, particle size, and drug loading and demonstrated up to a 9.3-fold enhancement in permeability across a Caco-2 monolayer for chitosan-cromoglycate particles, compared to the pure drug. This increased intestinal permeability led to improved pharmacokinetic performance of cromoglycate, e.g. up to 1.82-fold increase in relative oral bioavailability when dosed to Sprague-Dawley rats in a fasted state. These findings confirm the potential for chitosan particles to serve as an effective oral delivery vehicle for cromoglycate, with additional formulation optimization presenting the opportunity to reduce dosing frequency for treatment of allergy-based respiratory ailments.

Engineering mesoporous silica nanoparticles towards oral delivery of vancomycin

Vancomycin (Van) is a key antibiotic of choice for the treatment of systemic methicillin resistant Staphylococcus aureus (MRSA) infections. However, due to its poor membrane permeability, it is administered parenterally, adding to the cost and effort of treatment. The poor oral bioavailability of Van is mainly due to its physico-chemical properties that limit its paracellular and transcellular transport across gastrointestinal (GI) epithelium. Herein we report the development of silica nanoparticles (SNPs)-based formulations that are able to enhance the epithelial permeability of Van. We synthesized SNPs of different pore sizes (2 nm and 9 nm) and modified their surface charge and polarity by attaching different functional groups (-NH₂, -PO₃, and -CH₃). Van was loaded within these SNPs at a loading capacity in the range of ca. 18-29 wt%. The Van-loaded SNPs exhibited a controlled release behaviour when compared to un-encapsulated Van which showed rapid release due to its hydrophilic nature. Among Van-loaded SNPs, SNPs with large pores showed a prolonged release compared to SNPs with small pores while SNPs functionalised with -CH₃ groups exhibited a slowest release among the functionalised SNPs. Importantly, Van-loaded SNPs, especially the large pore SNPs with negative charge, enhanced the permeability of Van across an epithelial cell monolayer (Caco-2 cell model) by up to 6-fold, with P_app values up to 1.716 × 10^-5 cm s^-1 (vs. 0.304 × 10^-5 cm s^-1 for un-encapsulated Van) after 3 h. The enhancement was dependent on both the type of SNPs and their surface functionalisation. The permeation enhancing effect of SNPs was due to its ability to transiently open the tight junctions measured by decrease in transepithelial resistance (TEER) which was reversible after 3 h. All in all, our data highlights the potential of SNPs (especially SNPs with large pores) for oral delivery of Van or other antimicrobial peptides.