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Biomaterials

Biomaterials - Poster Session E

Poster O15 - Oral pegfilgrastim nanoparticles for mitigating hematopoietic acute radiation syndrome

Saturday, October 26, 2024
10:00 AM – 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  Acute Radiation Syndrome (ARS), or radiation sickness, is characterized by severe illness following whole-body exposure to high doses of penetrating radiation over a short duration1. A critical aspect of ARS is Hematopoietic Acute Radiation Syndrome (H-ARS), which is of paramount concern given current global nuclear tensions. Clinical symptoms such as neutropenia and thrombocytopenia underscore the urgent need for effective countermeasures. As an FDA-approved modulator of hematopoiesis, pegfilgrastim (PF) may provide a pharmacological intervention to mitigate H-ARS risks2. Despite its efficacy and extended half-life of 42 hours3, PF's subcutaneous administration poses challenges due to needle phobia and increased healthcare costs. Oral administration offers significant advantages, improving patient compliance and reducing costs. This study explores a novel, orally administered, biodegradable system for protein delivery. We focus on chitosan (CS) and its derivatives, known for modulating epithelial permeability, integrated with phenylboronic acid (PBA)-functionalized CS-PEI polymers (CP) (denoted as CPB). These polymers enhance stability, mucosal transport, and endosomal escape4. Our nanoparticles consist of a CPB shell and an inner core of PF and tannic acid (TA). TA, a natural polyphenol, facilitates protein binding, which is essential for effective cellular delivery5. The nanoparticles, formed by precomplexing PF with TA and encapsulating it with a cationic polymer shell, achieve good stability and minimal toxicity. This study presents an optimized nanoformulation for oral PF delivery, offering a dual-functional strategy to mitigate H-ARS and enhance the effectiveness of radiation countermeasures.

Materials and

Methods:  All radiation doses, ranging between 5-10 Gy of photon radiation, were administered at Columbia University’s Center for Radiological Research. Cationic CS-PEI polymers were synthesized according to established protocols4, and PBA was subsequently introduced into the CS-PEI polymer to enhance delivery efficiency by accelerating the unpacking of the CS polymer. To evaluate the polymer’s ability to mitigate inflammation post-radiation, a Quanti-Blue assay was conducted to assess the material’s efficacy in inhibiting Toll-like receptor (TLR) pathways. Additionally, to assess the protective effects of the nanoparticles on the human hematopoietic system, we performed a flow cytometry assay to test the differentiation of neutrophils using hematopoietic stem progenitor cells (HSPCs). For in vivo studies, we monitored the survival status and body weight of mice post-radiation to further assess the protective measures provided by the nanoparticles.

Results, Conclusions, and Discussions: In our previous studies, we observed an increase in inflammatory cytokine release by stromal cells in response to high levels of photon radiation. We identified irradiation-induced damage-associated molecular patterns (DAMPs) and measured their potential activation of TLR signaling pathways, which play a role in basal resistance to irradiation in animals and multiple radiosensitive tissues6. Our TLR assay implicated the activation of the TLR-3 pathways after photon radiation in fibroblasts, one of the critical stromal populations in human tissues. Interestingly, the selected NP copolymers demonstrated scavenging of the DAMPs and inhibition of the TLR-3 pathway, thereby alleviating the inflammatory microenvironment post-radiation. We then investigated the effect of CPB@PF NPs on radiation-induced damage in hematopoietic stem and progenitor cells (HSPCs). Flow cytometry analysis at days 7 and 14 post-treatment revealed that CPB@PF nanoparticles significantly enhanced the recovery and differentiation of HSPCs after radiation exposure. Finally, we demonstrated the ability of CPB@PF NPs to mitigate radiation-induced bone marrow damage in mice. In the mice study, the cohort receiving subcutaneous PF protein showed resilience to radiation-induced weight loss. Notably, mice receiving CPB@PF NPs orally demonstrated stabilization of body weight, with marginal declines compared to the control.
Survival analysis indicated that mice treated with CPB@PF (i.g.) or PF (s.c.) had significantly higher survival rates compared to the control group. Kaplan-Meier analysis revealed that the median survival time post-irradiation for the control group (IR+PBS) was approximately 15 days.
H-ARS presents significant clinical challenges due to its severe impact on hematopoietic progenitor cells. Current H-ARS treatments rely on subcutaneous (s.c.) injections of growth factors and cytokines, which face limitations in mass casualty scenarios. Developing oral delivery systems could enhance accessibility and improve healthcare responses to nuclear incidents. Our research introduces an oral formulation for PF, effective even when administered 48 hours post-exposure. Using CPB polymers, we developed a nanoparticle-based strategy for protein delivery. This approach employs TA to enhance protein stability and form uniform nanoparticles. Our study explores the therapeutic potential of these materials for radiation exposure-related disorders.

Acknowledgements (Optional):  This work is supported by TRISH NASA NNX16AO69A and NIH 1F31CA275733