1. a) What is packing parameter of lipid or surfactant? Calculate the packing pa
ID: 270671 • Letter: 1
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1. a) What is packing parameter of lipid or surfactant? Calculate the packing parameter of micelle, liposomes and bilayer. (10 points) b) Consider two types of single chain lipid of same hydrocarbon chain length with phosphate head group or 6-membered glucose head group. What type of structures are expected from these two lipids and why (5 points) c) Consider the following four lipids schematically shown below. Comment on the assembly of these lipids with change in pH (i.e. from acidic to neutral to basic) with explanation. (10 points) Hydrophilic Head Group MMw Hydrophobic Tail HOOC COOH COOH d)You are designing liposome based drug delivery system with three different lipids (A, B, and C see figure). All three lipids formed liposome of 200nm size and contained extremely high content of a hydrophilic drug in the liposome core. The drug release profile from the three liposomes are distinctly different. Draw qualitative sketches for amount of released drug vs. time curve for the three liposomes and explain why the drug release profiles are different in three types of liposome. (10 points) A Although the release profiles were different, all the profiles followed Higuchi model of drug release. Based on Higuchi Model, qualitatively identify two parameters which can influence the release profile. (5 points)Explanation / Answer
The aggregation of surfactants in organic or aqueous solution makes spherical micelle. Liposomes are spherical self-closed structures which are composed of curved lipid bilayers, which enclose part of the surrounding solvent into their interior. The core of the lipid bilayer consists of the tightly packed yet highly mobile lipid tails resembling a fluid phase.
(b) Two types of single chain lipid of same hydrocarbon chain length with phosphate head group or 6-membered glucose head group are likely to have a bilayer structure. It because, the phosphate head group are hydrophilic in nature which will repel reach other and will remain in the opposite poles. The same length hydrocarbon chain will aggregate oppositely.
(c) At acidic condition, the lipids will form either lipid caps or membrane patches. Basic treatment of lipid molecules are more complex than for acidic exposure, which forms irregular shapes. At neutral pH the lipids form stable unsupported bilayer.
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