Preparation and In Vitro Evaluation of Antibiotic Drug Immunoconjugates

The aim of the present study was to develop drug immunoconjugates (DIC) of antibiotics like Ampicillin trihydrate, Amoxycillin trihydrate, Streptomycin sulphate, Rifampicin and doxorubicin with Anti-D serum using different coupling methods. Protein content in AntiD serum was estimated by Lowry’s method. The conjugates were purified from unbound drug by dialysis. The drugs to antibody ratios were estimated by determining the quantity of antibacterial drugs coupled during coupling reactions by turbidimetric or colorimetric assay. The conjugates were tested for both antibody and antibacterial activities by simple in vitro methods. Slide agglutination test was used to know the retention of activity of the antibody qualitatively. The antibacterial activity was observed by reduction in turbidity due to growth inhibition. When glutaraldehyde method was used to couple the drugs the resulted DICs of Ampicillin trihydrate, Amoxycillin trihydrate and Streptomycin sulphate retained both antibody and antibacterial activities, while a direct linkage of Streptomycin sulphate to antibody resulted in the loss of antibacterial activity. Rifampicin was also linked to antibody by two methods. Upon direct linkage of Rifampicin to antibody retained both activities, but when linked by dicyclohexyl carbodiimide method, an antibody inactive preparation was resulted. Doxorubicin an anticancer antibiotic was also linked to antibody by glutaraldehyde method which retained antibody activity. Taken together, the results of our studies would be useful in the design of drug immunoconjugates with antibiotic drugs to treat specific infections in chemotherapy.