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# exam1 - Exam 1 03/21/06 80 points total 20.462J/3.962J...

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Exam 1 20.462J/3.962J 03/21/06 Spring 2006 80 points total Useful Equations: Expressions for the molecular weight (M) of degrading polymers vs. time: 1 = 1 + kt M = e M kt o M M o Charlier model for controlled release; amount of drug released at time t and depth of diffusion front: kt 1 ) 1/ 2 kt 1 Q ( t ) = A ˜ ( e k = A 2 C C D o ( e ) s o k kt 1 1/ 2 o s h ( t ) = 2 D C ( e 1 ) kC o π RT ( c ) Osmotic pressure developing across a membrane and resulting flux of water: L p () = J water δ Merrill-Peppas master equation for swelling of nonionic hydrogels: 2 1 = 2 v sp 2 , ( 1 ln( φ ) + φ , 2 s + χφ , 2 s ) , 2 s 1/ 3 M c M V 1 , 2 r , 2 s 1 , 2 s ⎢⎜ ⎟⎥ , 2 r 2 , 2 r 1 5/ 3 χ ) 2, s reduced form for highly swollen gels: 1 v sp ,2 ( 2 M 2/ 3 c V 1 2, r diffusion coefficient for a drug molecule (hydrodynamic radius r ) in a hydrogel with swelling ratio Q : 1 D = D H 2 O 1 r e ( Q 1 ) (cm 2 /sec) ξ 20.462J/3.962J S06 EXAM 1 1 of 10 9/5/06

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1. (20 points total) Choosing materials for in vivo applications . Answer the questions below with concise responses: 1-3 sentences or fragments, or qualitative sketches as appropriate. a. (5 points) Materials used in vivo can be placed into one of three classes, based on the ultimate fate of the material. What are these 3 classes, and what is the characteristic fate in vivo of materials of each type? b. (5 points) Draw the chemical structure and name 3 examples of bonds typically sensitive to hydrolysis under physiologic conditions; show the chemical structure of the immediately resulting products that are created by hydrolysis of each. 20.462J/3.962J S06 EXAM 1 2 of 10 9/5/06
c. (5 points) Biodegradable solid polymers undergo two distinct modes of breakdown, surface erosion or bulk erosion. Fill in the graphs shown below with qualitative representations/annotation to show what behavior you would expect for a material undergoing surface vs. bulk erosion.

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## This note was uploaded on 11/11/2011 for the course BIO 2.797j taught by Professor Matthewlang during the Fall '06 term at MIT.

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exam1 - Exam 1 03/21/06 80 points total 20.462J/3.962J...

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