Drug Delivery wi ith Temperature Sensitive L Liposomes Gino - PowerPoint PPT Presentation

Drug Delivery wi ith Temperature Sensitive L Liposomes  Gino Graziano  Chemistry Major  Santa Barbara City College  Santa Barbara City College  Faculty Advisor: Dr. Joseph Zasad dzinski  Department of Chemical Enginee ering  Mentor: Tallie Forbes Mentor: Tallie Forbes  Funding from National Institutes of Health (NIH)

Liposomes and Mecha Liposomes and Mecha anism anism  Phospholipid bilayer (cell mem mbrane material) Water-compatible head Water compatible head Water-incompatible tail Distinguishing Characteristic Distinguishing Characteristic  Naturally aggregates in “leaky” cancer tissue Mechanism:  Temperature Sensitive Temperature Sensitive Drug permeates membrane and is (releases contents at ~40 ° C) encapsulated

Big Picture g  More effective cancer trea atments by using temperature sensitive liposomes as vehicl p les for chemotherapy drugs py g Tumor Tumor Current Chemotherapy Liposome Delivery  Dispersed  Dispersed  Targeted  Targeted  Limited dosages  Larger effective dosage  Wide range of adverse effects  Reduced adverse effects  Controlled release Controlled release

Research Goals  What loading conditions giv ve the highest encapsulation efficiency? amount of drug encapsulated encapsulation efficiency = = total drug added to sample g p Variables  pH gradient ( Δ pH) pH gradient ( Δ pH)  Temperature  Time  Concentrations

 Using gold nanoshells for co  Using gold nanoshells for co ontrolled release ontrolled release M Mechanism M h i 1) ) Tethering of nanoshells to liposome 2) 2) ) Irradiation with near infrared laser ) Irradiation with near-infrared laser 3) ) Liposome is heated to release temperature 4) ) Drug is released Go old nanoshell Polymer tethers

Method: Fluorescence Method: Fluorescence e Spectroscopy e Spectroscopy  Measuring concentration of d rug through fluorescence intensity through fluorescence intensity y Generally, intensity is directly related to concentration: related to concentration: I = kC Proportionality constant constant  Fluorescence is measured before and after rupturing b f d ft t i Chal llenges loaded liposomes  Phot todecomposition  Self S lf -quenching hi g  Che mical interaction

Preliminary Results: E Preliminary Results: E Encapsulation Encapsulation  Change in fluorescence intens sity ( Δ I) is indicative of how much drug was encapsulat how much drug was encapsulat ted ted Increased pH Gradient Increased Loading Time 30.0 30.0 20.0 20.0 ∆ I ∆ I 10.0 10.0 0.0 0.0 2 hrs 16.5 hrs 3.4 4.4 Loading time ∆ pH I Increased Drug Amount d D A t I Increased Loading Temperature d L di T t 20.0 80.0 60.0 10.0 40.0 ∆ I Δ I 20.0 0.0 0.0 2.5 μ L 7.5 μ L 20°C 35°C Amount of drug added Loading temperature

Method Comparison 120.0 Two loading schemes used 90.0 Double buffer method  Manually established pH Δ I 60.0 gradient gradient 30.0 Ion gradient method  Passively established pH 0 0 0.0 gradient Same conditions Summary Increases in encapsulation seen when: h  pH gradient is increased Ion gradient loading shows  Loading time is increased to be much more efficient to be much more efficient  Loading temperature is increased L di t t i i d  Drug to lipid ratio is increased

Preliminary Results: R Preliminary Results: R Release Release  Loaded liposomes irradiated with near-infrared laser Without Nanoshells Without Nanoshells With Nanoshells With Nanoshells 30000 12000 Intensity Intensity 20000 20000 8000 8000 10000 4000 0 0 Bulk Temperature : 37 ± 1 ° C ure: 40 ° C 78.71% Release Release Temperat 78 71% Release

Conclusions Conclusions  Increasing encapsulation tren g p nd with increasing loading time, temperature, p H gradient and drug/lipid ratio  Ion gradient loading much m ore effective  Significant release observed g with nanoshells, suggests , gg relatively effective nanoshell tethering

Future Work: Future Work:  Leakage measurement L k t  Comparative release with d different tethering methods  More encapsulation data sp  More encapsulation data, sp pecifically regarding pecifically regarding time and concentration

Acknowledgments Acknowledgments Tallie e Forbes Dr. Joseph h Zasadzinski The Zasa adzinski Lab Dr. Jens s-Uwe Kuhn Dr Nich Dr. Nich holas Arnold holas Arnold Dr. Ar rica Lubin

Ion Gradient Method Ion Gradient Method (NH 4 ) 2 SO 4 NH 3 + + NH 4 HSO 4 U ncharged (leaves the liposome) Further equilibria: NH 4 HSO 4 NH SO H 3 + H 2 SO 4 SO H 2 SO 4 H + + + HSO 4 - Acidification of interior H + + HSO 4 - + SO 4 2-