Discipline: Biological Sciences
Veolanda A. Peoples - Alabama State University
Co-Author(s): Shannon Williams, Stephanie Barrow, Ronda Bibbs, Mamie T. Coats
Streptococcus pneumoniae is a respiratory pathogen which remains a major cause of morbidity and mortality worldwide in spite of available vaccines and antibiotics.The development of a novel antimicrobial drug is needed in order to conquer existing mutating S.pneumoniae isolates. Our goal was to investigate the usefulness of penicillin conjugated gold nanoparticles (AuNP-Pen) and encapsulated poly lactic-co-glycolic (PLGA-Pen) nanoparticles as potential multivalent antimicrobials inhibiting the growth of clinically relevant planktonic S. pneumoniae.
Methods: Gold nanoparticles (AuNP) were synthesized through the reduction of gold (III) chloride trihydrate (HAuCl4) with sodium borohydride (NaBH4) using the citrate reduction method.The final nanoparticle suspension yields a concentration of 2.5 x 10-4M. Penicillin was conjugated to the surface of the particles via formation of a thioether bond. PLGA-Pen nanoparticles were prepared by emulsification-diffusion method. All planktonic susceptibility studies were done over five hours of incubation in enriched media at 37°C. Biofilms were incubated at 37°C for four and twenty-four hours. Following incubation, viable colony counts were performed for all non-adherent bacteria. The S. pneumoniae isolates used were isolated from pediatric patients and had varying susceptibility to penicillin.
Results: The AuNP-Pen produced were 5-10nm spherical particles with 1.03 x 10-6 mol of penicillin/ng particle. While the encapsulated PLGA-Pen particles were considerable larger at 150-200nm. Following exposure to the nanoparticles, planktonic pneumococci showed reduced viability in the presence of the 0.125ng/µl AuNP-Pen and 0.25ng/µl PLGA-Pen when compared to AuNP and PLGA. However, independent of the level of penicillin susceptibility, there was not a significant difference in the inhibitory ability of free penicillin compared to that of AuNP-Pen and PLGA-Pen. Furthermore, while there was a trend for the isolates to survive less well in AuNP-Pen and PLGA-Pen than AuNP and PLGA, respectively; the difference was not statistically significant. However, AuNP in static biofilms statistically decreased viable non-adherent bacteria at four (P=0.0148) and 24 hours (P<0.05). Summary: While the tested nanoparticles were not effective against the antibiotic resistant S. pneumoniae, they will be examined against other pathogens. Also, because the use of these nanomaterials as therapeutics (against other bacteria) is possible, the genetic response of S. pneumoniae to the conjugate and encapsulated nanoparticles will be examined in the future.
Funder Acknowledgement(s): This work was supported by NSF-CREST (HRD-1241701); NSF-PIRE-1545884; and NSF-TPAC HRD-1432991
Faculty Advisor: Mamie Coats, email@example.com
Role: I performed all of this research myself, including MBC, SEM imaging, adherence assays, tissue culture, etc. A summer intern/student assisted me with the biofilm work.