Cromolyn sodium encapsulated PLGA nanoparticles: An attempt to improve intestinal permeation

Abstract

High hydrophilicity curtails the intestinal permeation of cromolyn sodium (CS) which in turn compels to compromise with its multiple biological activities. Hence, the present research was intended with an objective to develop CS encapsulated polylactide-co-glycolide (PLGA) nanoparticles (CS-PNs) for enhancing intestinal permeation. The CS-PNs were prepared by double emulsification solvent evaporation method (W₁/O/W₂). The “Quality by Design” approach using box-behnken experimental design was employed to enhance encapsulation of CS inside CS-PNs without compromising with particle size. The polymer concentration, surfactant concentration and organic/aqueous phase ratio significantly affected the physicochemical properties of CS-PNs. The optimized CS-PNs were subjected to various solid-state and surface characterization studies using FTIR, DSC, XRD, TEM and AFM, which pointed towards the encapsulation of CS inside the spherical shaped nanoparticles without any physical as well as chemical interactions. Ex-vivo intestinal permeation study demonstrated ∼4 fold improvements in CS permeation by forming CS-PNs as compared to pure CS. Further, in-vivo intestinal uptake study performed using confocal microscopy, after oral administration confirmed the permeation potential of CS-PNs. Thus, the findings of the studies suggest that CS-PNs could provide a superior therapeutic carrier system of CS, with enhanced intestinal permeation.

Introduction

Cromolyn sodium (CS), also known as disodium cromoglicate and sodium cromoglicate is a widely employed mast cell stabilizing agent in treatment of various allergic conditions such as allergic rhinitis, food allergy, mastocytosis as well as allergy induced bronchial asthma. For the indication, CS is currently administered through local routes, i.e., nasal and pulmonary route in the form of either solution or powder. Although, it is effective, the dose delivery variability and transient irritations at local dosing sites such as nasal mucosa, trachea and throat, making patients to feel inconvenience with prescribed therapy [1]. To this end, oral delivery of CS could easily circumvent the problems related to existing pharmacotherapy of CS. Nevertheless, poor physicochemical properties and high water solubility (100 mg/ml at 20 °C) impedes the absorption of CS across gastrointestinal track (GIT) which ultimately results in less systemically bioavailable (<1%) following oral administration [2]. Moreover, higher level of CS in systemic circulation might be useful for the treatment of atherosclerosis owing to its anti-inflammatory activity [3], [4].

Several formulation approaches such as prodrugs and liposomal delivery system have been designed in the past for improving oral permeation, but met limited success due to their intrinsic limitations [1], [5]. In this regard, polymeric nanoparticulate (PNs) based carrier system has been dedicated tremendous research emphasis for oral permeability enhancement on account of adoption of the special absorption pathways [6]. Upon oral administration, PNs are transported across GIT through selective uptake by M-cells in Peyer's Patches (PP) which directly drains them into blood circulation via intra-epithelial lymphoid cells of lymphatic system and thus, increased systemic availability of drug could be anticipated [7]. Additionally, sustained-release behaviour, biocompatibility, biodegradability and ease of modifying properties, etc. all of which making them highly prominent therapeutic carrier system and put forefront in the arena of nanomedicine [8].

Variety of polymers, including natural and synthetic, are being used in the preparation of PNs. Amongst all, United States Food and Drug Administration (USFDA) approved polymer, poly (lactic-co-glycolic acid) (PLGA) has been widely employed for oral drug delivery application. It has been proven to be safe due to its biodegradability and biocompatibility characteristics [7]. Miscellaneous engineering strategies, including nanoprecipitation, salting out, solvent evaporation, emulsion polymerization, emulsification diffusion, dialysis and supercritical fluid technique, etc. have been developed for the preparation of PNs. The selection of the particular fabrication method is primarily depends on the physicochemical properties of the drug molecule (i.e., solubility) and molecular stability [9]. Amongst all, a majority of the methods are developed to encapsulate hydrophobic compounds inside PNs. Contrary, encapsulation of hydrophilic drugs like CS, inside the matrix of PNs is really difficult because of rapid partitioning behaviour of drug into external aqueous phase during the fabrication. For better encapsulation of a hydrophilic molecule, the double emulsification solvent evaporation method (W₁/O/W₂) is commonly employed [6], [10].

In past, several researchers have tried to encapsulate different hydrophilic molecules inside PNs but found limited success due to lack of sufficient information regarding the influence of various formulation and process variables of the double emulsification solvent evaporation method, which critically affects the physicochemical properties of PNs such as particle size, encapsulation efficiency (EE) and polydispersity index (PDI). With progressive research, it has become imperative to assess the vital effect of independent variables by utilizing Quality by Design (QbD) approach based multivariate analysis [11], [12]. Therefore, 3-level, 3-fector Box Behnken Experimental Design (BBD) based logistic approach was employed to understand the influence of independent variables on dependent variables and for harnessing them in their permissible limits to obtain maximum encapsulation without compromising with the particle size and PDI.

So far, there have been no scientific reports in literature, on preparing CS encapsulated PNs using PLGA for improving intestinal permeation. In view of this information, with the objective of improving intestinal permeability, CS was encapsulated inside PLGA nanoparticles (CS-PNs) using quality by design approach. The Box Behnken Experimental Design was employed in order to study the influence of independent variables on dependent variables and to optimize CS-PNs. Further, optimized CS-PNs were characterized for various physicochemical properties, in-vitro studies and assessed for their ex-vivo as well as in-vivo performance in animals.