O25 - Improved Antimicrobial Properties of Platelet Like Particles

Saturday, October 11, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

PL

Preston Lewis

Undergraduate Researcher
North Carolina State University, North Carolina, United States

Co-Author(s)

Luke J. Tucker

Postdoctoral Researcher
North Carolina State University
Raleigh, North Carolina, United States

Primary Investigator(s)

Ashley C. Brown

Lampe Distinguished Professor
North Carolina State University and University of North Carolina at Chapel Hill
Raleigh, North Carolina, United States

Introduction: : Trauma-induced wounds often lead to long-term complications, particularly when infections are present. In chronic wound environments, microbial contamination can inhibit healing, increase the risk of systemic complications like sepsis, and complicate clinical management. While platelet-like particles (PLPs) have demonstrated promise in improving wound healing and reducing bleeding, the ability of first-generation particles to mitigate infection remains limited. Recent advances in the Brown Lab introduced silver nanoparticle-loaded PLPs (AgPLPs), which integrate antimicrobial action with hemostatic function. These particles are synthesized by polymerizing N-isopropylacrylamide and acrylic acid to form ultralow crosslinked (ULC) microgels, which are then loaded with silver nanoparticles and functionalized with fibrin-specific antibody fragments. However, further optimization is warranted to enhance silver and antibody binding. This study explores the development of a modified variant, ULC+, which is created by increasing acrylic acid content through controlled deamination via hydrolysis. The aim is to improve particle functionality by increasing the availability of binding sites for both antimicrobial agents and targeting proteins. The overarching goal is to develop a multifunctional biomaterial with improved therapeutic potential for infected and trauma-caused wounds.

Materials and

Methods: : ULC particles were first synthesized by polymerizing N-isopropylacrylamide and acrylic acid using established protocols. To create ULC+, the base ULC particles underwent additional hydrolysis to increase their acrylic acid content, thereby generating more carboxylic acid sites for binding. The resulting ULC+ particles were then loaded with silver nanoparticles via a chemical reduction reaction using silver nitrate and sodium borohydride, forming AgULC+. Fibrin-specific antibody fragments were conjugated to both AgULC and AgULC+ particles to create targeting systems (AgPLP and AgPLP+).

To characterize these particles, titration assays were conducted to quantify differences in carboxylic acid group content by measuring NaOH volumes needed to reach equivalence points. Dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) were used for size characterization. Atomic force microscopy (AFM) was used to assess particle morphology and deformability. Transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS) are being employed to confirm silver incorporation and quantify loading. A minimum inhibitory concentration assay was used for preliminary antimicrobial evaluation against Staphylococcus aureus. Absorbance values were used to determine bacterial viability across varying concentrations of ULC, AgULC, ULC+, and AgULC+.

Results, Conclusions, and Discussions:: Initial titration studies revealed that ULC+ required a significantly lower average volume of NaOH to reach equivalence compared to ULC, supporting an increase in carboxylic acid content. This indicates that ULC+ possess a higher baseline binding capacity, providing more accessible sites for conjugation of silver nanoparticles and antibody fragments. AFM also showed no differences in the topography of ULC+ and ULC particles, suggesting no changes in particle stiffness and structure due to increased acid functionality.

Preliminary antimicrobial analysis using a 96-well plate assay demonstrated enhanced bacterial suppression by AgULC+ compared to AgULC, ULC+, and unmodified ULC particles. These findings suggest that the dual action of increased silver content and fibrin-targeting may result in more efficient delivery of silver nanoparticles to infected tissues. Absorbance values at higher particle concentrations showed a clear trend: AgULC+ had the strongest inhibitory effect against Staphylococcus aureus, supporting its potential as a more effective wound treatment agent.

These results support the hypothesis that structural modifications to ULCs improve functional performance. By enhancing the availability of binding sites through acrylic acid enrichment, AgULC+ demonstrates improved antimicrobial activity and lays the groundwork for a robust, multifunctional platform. Future work will focus on quantifying silver content using ICP-MS and evaluating fibrin-binding efficiency through clot-on-slide assays. Additional in vitro testing will further assess biocompatibility and efficacy under simulated wound conditions. If successful, AgULC+ could represent a next-generation wound healing material that combines soft-tissue conformability, infection control, and targeted delivery, addressing a significant clinical challenge in trauma and chronic wound care.

Acknowledgements and/or References (Optional): :