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Gold Nanoparticle-Targeted Laser Therapy for Enhancement of Antibiotic Efficacy against MRSA Biofilms



The Centers for Disease Control and Prevention has determined that antimicrobial resistance, compounded by an ever waning number of antibiotics in the pharmaceutical pipeline, to be one of the main threats to public health.6 In the United States alone, approximately 2 million people contract hospital-acquired infections every year, resulting in 90,000; about 70% of the bacteria associated with these infections are antibiotic-resistant.5 In fact, multidrug-resistant infections cause more deaths per year than breast and colon cancer combined,6,13 and the annual cost for treatment of infection-related illnesses in the United States is estimated at $28 to $45 billion.14
The urgent need to address this health care crisis has helped drive the discovery of novel nanomaterial-based technologies with advanced capabilities for targeting and control of drug delivery, real-time monitoring of therapeutic outcomes, and phototherapeutic and photodiagnostic applications. In particular, leading-edge research from our laboratory and elsewhere15 demonstrates that exploiting the strong interactions between GNPs and lasers to destroy biofilms has the potential to enhance treatment of refractory infections and, thus, could have a significant positive impact on quality of life for patients and ease the economic burden on healthcare systems throughout the world.
GNP-targeted laser therapy would most likely find its greatest utility in eradicating cutaneous infections or debulking localized abscesses due to the current limitations in precise delivery of nanoparticles to deep tissues and sites without sufficient vasculature. It is anticipated that this therapy could improve debridement and removal of recalcitrant biofilms for synergistic enhancement of mainstay antibiotic treatments in chronic, recurrent wounds. Elderly, diabetic, and immunocompromised patients with serious nonhealing wounds that lead to significant morbidity and mortality may especially benefit.
Future development and refinement of the technique may also allow its application for removal of relatively accessible biofilm infections in the oral cavity, around catheters, and possibly on various types of abiotic surfaces. Other future innovations for advancing this therapy include use of longer-wavelength lasers in the near-infrared region for increased penetration into tissues, incorporation of broader spectrum GNP-targeting strategies to attack a wider range of pathogens, and development of multifunctional nanoparticles that would allow delivery of photothermal therapy in combination with antibiotics or anti-biofilm agents.  
Nancy J. Millenbaugh, PhD, is a principal investigator in Naval Medical Research Unit San Antonio's (NAMRUSA) Maxillofacial Injury and Disease Department located at Joint Base San Antonio, Fort Sam Houston, Texas. Dr. Millenbaugh leads the NAMRU-SA project investigation utilizing nanoparticles and laser energy to combat infectious disease. Dr. Millenbaugh has been with NAMRU-SA for over six years and received her BS in Pharmacy and her PhD in Pharmaceutics and Pharmaceutical Chemistry from Ohio State University.   

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