Bio-functionalized Polymeric Nanocarrier System for Targeting Inflamed Intestinal Mucosa

Abstract

Inflammatory bowel disease (IBD) is the chronic inflammation of the Gastrointestinal tract (GIT). Ulcerative colitis (UC) is one of the major types of IBD that confines to the colon. The available conventional therapies for the treatment of IBD are less promising because of pathophysiological, and cellular barriers. In this context, nanocarrier-based drug delivery system specifically delivers various therapeutic agents to the target area. Nanocarriers made up of pH-sensitive polymers protect against drug degradation and absorption in the upper GIT. The combination of pH-sensitive polymer with a sustained-release polymer like PLGA release and concentrate the drug at the target area for a prolonged time. Further, to overcome inter and intra-cellular barriers at the colon, ligand-based strategy enables specific targeting of colon cells and recruited immune cells like macrophages via specific surface receptors overexpressed under inflammation. Based on the altered immunological condition of the colon in UC, various surface receptors like macrophage galactose type lectin-C (MGL-2) and transferrin receptor (TFR-1) are exploited for colon drug delivery purpose. We aimed to develop stimuli sensitive-ligand anchored sustained release polymeric nanocarriers to target the colon for prolonged duration and bypass obstacles via the oral route. The outer stimuli sensitive coat dissolves at the colon microenvironment and exposes underneath drug-containing ligand anchored PLGA nanocores that target the overexpressed surface receptors and releases the drug for a prolonged duration. Under stimuli sensitive-ligand anchored polymeric nanocarriers based rationale, we have developed three strategies to target inflamed colon through the oral route. In the first one, we have prepared Dexamethasone (Dexa) loaded D-galactose-PLGA nanoparticles (GAL-PLGA NPs) and stimuli sensitive Dexa loaded D-galactose/Eudragit S100/Pullulan nanocargoes (Dexa-GP/ES/Pu NCs). The later have all attributes to target colon because of dual stimuli sensitive coat of Eudragit S100 (ES) and Pullulan (Pu) that dissolved under pH and microbial enzymes of the colon. Further, ligand anchored galactose-PLGA (GAL-PLGA or GP) core has a high affinity towards MGL-2, that is overexpressed on the surface of macrophages at the colon. The Dexa-GAL-PLGA NPs were developed under systemic quality by design (QbD) approach and Box-Behnken design. Further, coating with ES/Pu generated Dexa-GP/ES/Pu NCs that have appropriate physicochemical properties, thermal stability, negligible interactions between excipients, and retardation of drug release at pH 1.2 and sustained xvii drug release at pH 7.4, biocompatible and good uptake by the colon and macrophage cells. The Dexa-GP/ES/Pu NCs demonstrated efficient targeting and amelioration of Dextran sulfate sodium (DSS) induced colitis. Under the second approach, we have developed Tofacitinib citrate (Tofa) loaded PLGA/transferrin nanocarriers (Tofa-P/tfr NCs) using QbD and Box-Behnken design. Furthermore, Tofa-P/tfr NCs were modified to formulate nanoshells (NSh) i.e., Tofa-LP/tfr NSh and Tofa-LP/tfr/ES NSh with enhanced properties because of lipidic content (L) in the core that facilitates more drug content to be encapsulated, controlled drug release and have some protective effects on intestine mucosa. The pH-sensitive nature of Tofa-LP/tfr/ES NSh enabled more colon-specific action. Tofa-P/tfr NCs, Tofa-LP/tfr NSh and Tofa-LP/tfr/ES NSh have an adsorbed tfr ligand that facilitated direct binding with TFR-1 receptors. The minimal drug release at pH 1.2 was observed with Tofa-LP/tfr/ES NSh. These three nano-formulations have extensive uptake potential. Tofa-LP/tfr NSh and Tofa-LP/tfr/ES NSh were more biocompatible than Tofa-P/tfr NCs. All Tofa-P/tfr NCs, Tofa-LP/tfr NSh and Tofa-LP/tfr/ES NSh proved to be efficacious in restoring inflammation in the DSS-colitis model as manifested from restored clincal and inflammatory indices. However, Tofa-LP/tfr/ES NSh had the superior action because of multiple characteristics. Under the third strategy, tacrolimus (TAC) loaded nanocarriers (NCs) were developed with adhered L-Lysine content on PLGA (P/Lys), coated with dual ES100 and EL100 (ES-L100) pH-sensitive coat. The combined rationale is developed to counter the inter- and intra-individual variations and have more control over drug release at colon. TAC-P/Lys NCs and TAC-P/Lys/ES-L100 NCs were developed with optimal characteristics. ES-L100 coated formulation have more retardation of drug release at pH 1.2 than uncoated nano-formulation. Both TAC-P/Lys NCs and TAC-P/Lys/ES-L100 have good biocompatibility and uptake potential into the caco-2 cells and macrophages. TAC-P/Lys NCs and TAC-P/Lys/ES-L100 have promising therapeutic effects in the oxazolone (OXA) induced colitis model, as manifested through the endoscopy, morphological parameters, histology, inflammatory proteins, and mediators’ levels. Further, TAC loaded nanocarriers inhibited inflammatory pITK levels in the T-cells, as indicated through immunohistochemistry, flowcytometry, and RT-PCR. In short, TAC-P/Lys/ES-L100 NCs have superior therapeutic efficacy in the OXA-colitis model as compared to uncoated TAC-P/Lys NCs. However, further investigations are required to check the therapeutic efficiency of all these nano-formulations on a relevant bigger animal model and to translate this concept into clinical studies.