Evaluation of the clearance characteristics of liposomes in the human nose by gamma-scintigraphy

The nasal cavity possesses many advantages as a site for drug delivery, such as, ease ofadministration, applicability for long term treatments and a large surface area for absorption.one important limiting factor for nasal drug delivery is the limited time available for absorptionwithin the nasal cavity due to mucociliary clearance, several drug delivery systems includingdifferent kinds of microspheres and liposomes have been tried for encapsulation of drugs andincreasing the residence time in nasal cavity. in this study the clearance rate of three kinds ofliposomes: neutral [phosphatidylcholin (pc) and cholesterol (chol)], cationic (pc, chol andstearylamine) and fusogenic (pc, chol, dioleoylphosphatidylethanolamine) was determined bygamma scintigraphy with lactose powder being used as negative control.liposomes were prepared by dehydration-rehydration method. 99mtc labeled liposomes wereprepared using technetium pertechnetate in the presence of a potent reducing agent, stannuschloride, the labeling procedure was set in a manner that each 150 ~i of liposome suspensionscontained 2 mbq of radioactivity. labeling efficiency was calculated by paper chromatographyusing acetone as mobile phase. each delivery system containing 2 mbq of activity was sprayedinto right nostril of four healthy volunteers and one-minute static views were repeated each halfhour until 4 hours. clearance rates were compared using two regions of interest (rols); theinitial site of deposition of particles, and all of nasopharynx region. the clearance rate of eachone of iiposomes was calculated after applying the physical decay corrections,the mean labeling efficiencies for neutral, cationic and fusogenic liposomes were calculatedas 91%, 20% and 69%, respectively. the cleared percent of preparations from nasopharynxregion after 4 hours was determined as follows: neutralliposomes l8±2.9%; fusogenic liposomes53.5± 1.2%; cationic liposomes 69.7±4.2%; lactose powder 74.5±4.9%. neutral iiposomesshowed the lowest clearance rate compared to lactose powder (p