Student Seminole High School LAKE MARY, Florida, United States
Introduction: Orthopedic casts and prosthetics, crucial in managing bone fractures and limb replacements, face persistent challenges from bacterial infections which can extend recovery and escalate to severe complications. Despite the technological advancements, bacterial infection remains a significant challenge in the postoperative phase, prolonging recovery times and potentially leading to life-threatening complications. Additionally, not much has changed in the past several decades in the design of plaster-based prosthetics for use in prosthetics following fracture or limb replacement surgeries. This study looks to the creation of the next generation of these prosthetics using some exciting new materials that show promising biomaterial properties. Aerogels, a class of highly porous materials with ultralow density, have also been investigated for their potential application in the biomedical field. The hydrophobic nature of silica aerogels, in particular, is known to limit the adhesion of bacteria to surfaces, providing an added layer of protection against infections. Silver nanoparticles (AgNPs) have garnered particular attention for their broad-spectrum antimicrobial activity and limited toxicity toward human cells. The incorporation of AgNPs into various medical devices, including catheters and wound dressings, has demonstrated promising results. In this study, it is hypothesized that the introduction of aerogel and silver nanoparticles on the surface of orthopedic casts and prosthetics will significantly inhibit bacterial growth when compared to the growth of E.coli on a control surface without the aerogel and silver nanoparticle treatment. The findings here will aid in development of an improved orthosis that is lightweight, antimicrobial, and modular orthopedic casts and prosthetics.
Materials and
Methods: For this study, the following experimental setup was employed to evaluate the impact of graphene-infused nanoporous aerogel and silver nanoparticles on the growth of Escherichia coli K12 in various mediums. A total of 59 petri dishes were divided into five groups, with each group receiving different treatments: Group A (no treatment), Group T (control), Group P (aerogel), Group Q (aerogel with Ag nanoparticles), and Group B (plaster cast). Agar gel was poured into the petri dishes in groups T, P, Q, and B to create a consistent growth medium.
Following the initial preparation, gypsum plaster was molded into sample pieces and placed in the designated petri dishes. Groups P and Q received a uniform layer of aerogel, and Group Q additionally had Ag nanoparticles evenly distributed over the aerogel using a fine-haired brush and sieve method. The inoculation process involved transferring a bacterial monoculture of E. coli into the petri dishes of groups T, P, Q, and B using sterile techniques and inoculation loops. Each group was monitored under strict experimental controls to ensure consistency across all samples.
After a 48-hour incubation period, the colony growth was visually inspected and photographed in all petri dishes under varying lighting conditions to aid in counting and analysis. The number of bacterial colonies was meticulously counted, with distinctions made between clumps and individual dots of bacteria. Counting was repeated and the average count was considered for analyses. Meticulous care was taken to properly dispose of biohazard materials at the conclusion of the experiments.
Results, Conclusions, and Discussions: The analytical approach utilized for evaluating the efficacy of different antimicrobial treatments comprised a sequential three-step non-parametric testing procedure. Initially, the Mann-Whitney U Test was applied to detect any significant disparities in bacterial colony counts between the plaster and the control. Subsequently, the Kruskal-Wallis test was employed to ascertain differences among the control, Aerogel, and AgNP infused Aerogel. Finally, a subsequent Mann-Whitney U Test focused on comparing groups directly.
The statistical analysis indicates that there is a significant difference in the growth of E.coli bacteria on the surface of control (or orthopedic casts) as compared to aerogel and aerogel infused with silver nanoparticles (p < 0.005). As hypothesized, AgNP infused aerogel demonstrated the least colony counts for E. Coli as compared to the other treatments (p < 0.005). While aerogel alone had a significant effect on the reduction of E. Coli colonization (p < 0.005, when compared to control or plaster), the reduction in colony count was greater when used with addition of AgNP (p < 0.05). Aerogel is effective even when it is not binding to the substrate. This is expected and well-explained by the mechanism.
These findings support the potential antimicrobial properties of silver nanoparticles when applied to aerogel surfaces. The introduction of aerogel with its highly porous structure and silver nanoparticles on the surface of orthopedic casts and prosthetics can effectively inhibit the growth of E.coli bacteria, which may lead to a decreased risk of infection in patients using these devices. Aerogel, specifically metal nanoparticle induced surfaces, can be mass produced cheaply for it to be widely adopted for such applications. This study provides the scientific basis for the next step of this study – creating a removable orthosis/cast in combination with graphene or metal nanoparticle infused aerogel fabric. A lean, minimal design of a prosthetic that can be additively built will be greatly valuable during prolonged space flights, such as on trip to Mars. Orthosis can be printed to exact size on 3D printers and used with carbon fiber and aerogel+AgNP lining for an effective rigid and removable prosthetic support.
Acknowledgements (Optional): 1. Chia, D., & Yeo, J. (2020, November). Minimizing infectious spread during fabrication of casts and orthotics for hand fractures in COVID-19 patients. Annals of physical and rehabilitation medicine. Retrieved October 24, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7405915/ 2. Ning Yan, Yabin Zhou, Yudong Zheng, et. al., Antibacterial properties and cytocompatibility of bio-based nanostructured carbon aerogels derived from silver nanoparticles deposited onto bacterial cellulose, RSC Advances, #118, 2015. 3. Bifunctional Material With Organic Pollutant ... - ACS publications. (n.d.). Retrieved October 25, 2022, from https://pubs.acs.org/doi/10.1021/acssuschemeng.8b04251 4. Dunbar, B. (2015, April 15). Aerogels: Thinner, lighter, stronger. NASA. Retrieved October 24, 2022, from https://www.nasa.gov/topics/technology/features/aerogels.html 5. Walker, B., Amato, C., Palyvoda, O., Vangipuram, S., Weaver, M., Sayeed, Z., Talha Padela, M., & Yassir, W. K. (2020, January 21). Prevalence of bacterial contamination of casting material in a pediatric population. International journal of pediatrics. Retrieved October 24, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6996683/
