Applications of Polymerized Vesicles Seung-Woo Son, Complex System and Statistical Physics Lab.

Motivation : Nature and Membranes What is a membrane structure ? Simply lipid bilayers or vesicles !

What is Vesicles? –Spherical closed bilayer structures –Surfactants comprising two alkyl chains and a cationic polar head (ammonium, phosphate or zwitterion) cf.) micelles, microemulsions, bilayers Liposomes ( a special case of vesicles ) –Vesicles formed from naturally occurring lipid molecules. Lipid : 비극성 유기용매의 추출에 의해 세포나 조직으로부터 분리되는 자연계에 존재하는 유기분자 ( 종류 : 지방, 왁스, 콜레스테롤, 스테로이드 ) * Other useful expression… –In vivo : 생체에서 … –In vitro : 시험관에서 … Introduction : Glossaries of Soft Matters

Physics of Soft Matters Micelles, bilayers, vesicles and biological membranes –Self-assembly of certain amphiphilic molecules –Association colloids or complex fluids –Soft, flexible (fluid-like) unlike solid particles, rigid macromolecules(ex.DNA) –Van der Waals force, hydrophobic, hydrogen-bond, screened electrostatic interactions etc.(not covalent bond or ionic bond) –Solution conditions(electrolyte concentration, pH, temperature, etc.) change the size and shape of molecule aggregates. Ref. Jacob N. Israelachvili, “Intermolecular and Surface Forces” Ch 16, 17

Special Character of Vesicles Diameter ~ 10nm, thickness 4~5nm spherical water-filled pockets Several weeks lifetime – Great kinetic stability – Lower surfactant exchange rate – Higher number of surfactant molecules Spherical micellesMicroemulsionsVesicles Mean molecular weight 1-3  > 10 7 Aggregation number Diameter ( Å ) Monomer exchange rate (s) > 1 Aggregate lifetime – 1 sVery longWeek, month Dilution in water DestroyedAlteredStable

Polymerization of Vesicles The aim of polymerization is to fix the structure –To observe the shape of vesicle, to measure the size –Control the size, rigidity, permeability –Actually unlimited lifetime(several month) : greater stability –To clarify the mechanism of vesicle fusion

Polymerization Strategies

Applications of Polymerized Vesicles (1) : DDS Active molecule transport –Pharmacology : selectively carry a compound to a preselected site in the organism. –pH, temperature, photochemical isomerisation, enzymes, etc.

Applications of Polymerized Vesicles (2) : catalysts Ideal medium for the formation of small and uniform colloidal particles of metals or oxides. –Potassium tetrachloroplatinatr ( K 2 PtCl 4 ) + polymerisable surfactants : extremely efficient colloidal platinum catalyst. Artificial photosynthesis –Photochemical solar-energy conversion using colloidal semiconductor –Decomposing water

Summaries Vesicles 의 모양와 성질에 대해서 Polymerization 을 연구해야 하는 이유 Polymerization 방법들 Polymerized vesicles 의 응용

Motivation :

Applications of Polymerized Vesicles (2) : photosynthesis