APPLICATION OF POLYMERS AND POLYMER-BASED NANOPARTICLES TOWARDS THE AMELIORATION OF CHRONIC RESPIRATORY DISORDERS

Author

Kalindu D.C. Perera, University of Rhode IslandFollow

Date of Award

2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Pharmaceutical Sciences

Department

Biomedical and Pharmaceutical Sciences

First Advisor

Jyothi U. Menon

Abstract

Chronic respiratory diseases (CRDs) affected upwards of 400 million people worldwide as of 2019, accounting for 7.54% of the then global population. CRDs encompass a wide range of pathophysiologies, as a function of the specific cell/s and tissue structures affected within the pulmonary environment. These may be obstructive (e.g.: chronic obstructive pulmonary disorder, COPD) or restrictive in nature (e.g.: pulmonary fibrosis, PF). Hypersecretion of mucus (at times, with increased- or hyperviscosity) is a common hallmark of obstructive CRDs, while extensive tissue fibrosis is a hallmark of many restrictive CRDs. Thus, while it is not possible to formulate a “silver bullet” for all CRDs, there exists an opportunity to target common pathophysiological features in order to better treat these conditions.

A significant part of treating such common disease features is currently achieved through traditional small molecule drugs. These suffer from poor patient compliance, off-target effects, poor in vivo absorption (due to various biological barriers), or simply from many separate pharmaceutical agents being required to effect even minor alleviation of disease features. Many of these may be addressed through the application of polymer-based drug delivery solutions, particularly nanoparticles, which are well-absorbed, and can be custom-designed for a desired application, including targeting, sustained/controlled drug release, multi-drug encapsulation and differential release profiles.

The key aims of this dissertation were to: a) design and characterize poly(lactic-co-glycolic) acid (PLGA)-based nanoparticles for the amelioration of fibrosis in PF and b) design and characterize PLGA-based nanoparticles to address chronic airway inflammation and resultant airway obstruction by hypersecreted and/or hyperviscous mucus. A secondary aim that developed within the course of the above work was the development of a novel, thermoresponsive poly(N-isopropylacrylamide) (PNIPAm)-based photoink for 3D digital light processing (DLP) bioprinting.

Exploiting the ability of pectin from citrus peel to ameliorate fibrosis (through its interaction with galectin-3), citrus pectin (CP)-coated nanoparticles were synthesized. These were shown to experience significant preferential uptake by fibrotic pulmonary fibroblasts in a dose-dependent manner, and were highly cytocompatible. In vitro evaluation of these particles’ efficacy showed marked reductions in pro-fibrotic markers such as galectin-3 (gal3), α-smooth muscle actin α-SMA, and β-catenin within 24 h. The deposition of collagen (a key indicator of fibrosis) was also shown to be reduced in vitro. In keeping with these results, in vivo data from a murine model of bleomycin-induced PF showed even more promising data, with significant downregulation of the aforementioned markers (among others) and an apparent reversal of fibrosis within 72 h of treatment.

Recognizing the limitations of this proof-of-concept formulation, a version with a modified CP (in the form of Pectasol C: PTS) coating was synthesized, encapsulating a payload of the anti-fibrotic nintedanib (NIN). Maintaining their propensity for higher uptake by fibrotic cells and a lack of cytotoxicity, these showed a significant additive effect of the formulation’s two anti-fibrotic components in vitro. This latter was observed through the reduction in levels of gal3, α-SMA and pSMAD3 in fibrotic fibroblasts. These trends were observed both in conventional 2D cell cultures as well as in a model of fibroblastic foci, carried out using fibroblast spheroids. While confirming the efficacy of this formulation, these in vitro studies also underscored the subtle differences in nanoparticle uptake and response dynamics in traditional and more physiologically-relevant models.

To aid in the generation of the aforementioned spheroids, a PNIPAm-based photoink for use with the Cellink LumenX series of DLP bioprinters was developed. This photoink was optimized through multiple full factorial experiments, with a target lower critical solution temperature (LCST) approaching that of standard cell culture conditions. The hydrogels produced by the final optimized formulation (LCST= 36.8°C) displayed marked changes to their rheological properties at the LCST, with direct impact on shrinking and swelling behaviour. Rapid shrinking (85-90% loss of water within 10 mins.) at the LCST allowed for microwell arrays generated with this photoink to rapidly compact spheroids. Subsequent swelling at room temperature allowed for facile removal of spheroids, with no reductions of viability in seeded cells. Apart from microwell arrays, the photoink also showed itself to be capable of being applied for thermoresponsive drug release, and for the printing of structures with fine features in the order of >40-200 µm (dependent on axis).

Finally, lipid-polymer hybrid nanoparticles were developed as an inhaled, multi-functional drug delivery platform for use in obstructive CRDs. Dipalmitoylphosphatidylcholine (DPPC) was added as a coating to PLGA nanoparticles. The lipid shell was designed to rapidly release a mucolytic in the form of N-acetylcysteine (NAC), and the polymer core for sustained release of the anti-inflammatory all-trans retinoic acid (ATRA). These particles showed themselves to be capable of exerting significant changes in both bulk- and microrheology of an in vitro model of cystic fibrosis mucus, effecting significant decreases in local and bulk viscosity. This aided not only more rapid movement of these particles through the mucus (avoiding putative clearance), but also assisted in more rapid amelioration of underlying epithelial inflammation. Assessment of this combinatorial effect in an organ-chip model of airway inflammation confirmed this effect, with significant reductions in levels of pro-inflammatory cytokines IL-6 and -8 after just 72 h of treatment.

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Recommended Citation

Perera, Kalindu D.C., "APPLICATION OF POLYMERS AND POLYMER-BASED NANOPARTICLES TOWARDS THE AMELIORATION OF CHRONIC RESPIRATORY DISORDERS" (2025). Open Access Dissertations. Paper 4429.
https://digitalcommons.uri.edu/oa_diss/4429