Purpose: Infections caused by Methicillin-Resistant Staphylococcus aureus (MRSA) in humans are difficult to treat and are resistant to most of the β-lactam antibiotics like cefazolin. The infection is associated with inflammation which triggers and accumulate pro-inflammatory macrophages. These macrophages are characterized by the folate receptor overexpression which can be used as a biomarker to selectively target the infected site. Vancomycin is the first choice drug used in the treatment of MRSA infections but gave poor clinical outcome due to a high dose which led to nephrotoxicity. The current study is to develop a folate-targeted liposomal formulation to deliver vancomycin with high drug payload at the infected site for a sustained release action and thereby reduced MIC.
Methods: Folate receptor expression: Immunohistochemistry (IHC) was performed for Control vs MRSA infected mouse eye tissue to check the folate receptor expression on the macrophages at the infected site.
Optimization: Empirical optimization was done by varying parameters like lipid concentration. 5 liposome batches of different lipid concentrations were prepared. The best batch was selected in terms of particle size, %drug loading and serum stability.
Drug payload at the infected site: The selected formulation was used to perform in vivo study with Rhodamine conjugated vancomycin liposome (LVAR) vs free vancomycin(VAR) administered through intraperitoneal injection in MRSA infected mouse (infected thigh tissue). After treatment for a specified time, mice were euthanized and thigh tissues were collected. Harvested tissues were embedded in paraffin glass slides and fluorescence imaging was done to evaluate the sustained release of the drug.
Results: The IHC study inferred that compared to the control, MRSA infected eye tissue had higher expression of the folate receptor. This led to the development of folate targeted vancomycin liposomes. % Drug loading and serum stability showed a comparative trend with respect to cholesterol composition of the 5 batches. The liposome formulations have followed a pattern (i) increase of vancomycin loading with a decrease of cholesterol amount, (ii) increase of serum stability with an increase of cholesterol in liposomes. The batch of liposome with optimum %drug loading and serum stability was selected for in vivo to check the sustained release of the drug. The higher accumulation of LVAR with higher fluorescence intensity compared to VAR indicate the active MRSA targeting of vancomycin in liposome formulation, correlating profound therapeutic benefit in MRSA.
Conclusion: The preliminary results of initial optimization direct towards developing a robust liposomal Vancomycin formulation that may show high potential for clinical translation on extensive optimization by Quality by Design (QbD) approach. The fluorescence imaging showed high drug payload at the infected site for liposomal vancomycin vs free vancomycin which infers that targeted liposomes are more efficient in giving sustained release of vancomycin which reduces the MIC and reduces nephrotoxicity of the drug.
Reference: Materials 2018, 11(7), 1245; https://doi.org/10.3390/ma11071245.
Samaresh Sau– Detroit, Michigan
Kushal Vanamala– Detroit, Michigan
Ketki Bhise– Detroit, Michigan
Miao Zhao– MADISON, Wisconsin
HIRAM SANCHEZ– MADISON, Wisconsin
Anthony Bally– Detroit, Michigan
DAVID ANDES– MADISON, Wisconsin
Michael Rybak– detroit, Michigan
Arun Iyer– Detroit, Michigan