Biocompatibility: Evaluation and Risk Assessment

Question 1

toxicity

Answer 1

describes the ability of a material to damage a biological system by chemical means
may be local or systemic

Question 2

immunotoxicity

Answer 2

describes the adverse effects on the structure and function of the immune system

Question 3

autograft

Answer 3

donor and recipient are the same person

Question 4

allograft

Answer 4

donor and recipient are from the same species

Question 5

xenograft

Answer 5

donor and recipient are from the different species

Question 6

risk is a combination of

Answer 6

hazard and exposure

Question 7

in vitro biocompatibility assessment

Answer 7

isolated cells derived from animal or human tissues are grown in culture plates and used for testing

Question 8

three primary cell culture assays are used for evaluating compatibility

Answer 8

direct contact
agar diffusion
elution testing

Question 9

cell lines

Answer 9

immortalized cells, some are from normal cells, others from tumors
effectively they are clones of the original donor
good: established and commercially available, genetically uniform, lower cost
bad: some genetic manipulation required to achieve immortality, may not function as target cells type, may not be available for target cell types and species
not for human use due to immunogenicity, research tool only

Question 10

primary cells

Answer 10

isolated directly from animal or human tissues
good: closest to the real cell, can be patient specific
bad: difficult to grow, limited proliferation capacity, heterogeneous, immunogenic, difficult to reproduce

Question 11

how can i test biocompatibility on a specific patient

Answer 11

stem cells
personalized induced stem cell will carry your genetic characteristic and unique response toward biomaterials

Question 12

direct contact assay

Answer 12

biomaterial is placed directly over or under cultured cells

Question 13

agarose diffusion assay

Answer 13

biomaterial is separated from cultured cells by a thin layer of agarose

Question 14

elution assay

Answer 14

biomaterial is incubated in medium for an extended period of time to extract leachable compounds

the conditioned media will then be used to culture cells in a separately prepared dish

Question 15

direct contact advantages

Answer 15

no extract preparation
zone of diffusion
target cell contact with material
standardize amount of test material or test indeterminate shapes

Question 16

disadvantages of direct contact

Answer 16

cellular trauma if material moves
cellular trauma with high density materials

Question 17

agar diffusion advantages

Answer 17

no extract preparation
zone of diffusion
can test one side of material, independent of material density

Question 18

disadvantages of agar diffusion

Answer 18

requires a flat surface
risk of absorbing water from agar
solubility of toxicant in agar

Question 19

advantages of elution

Answer 19

dose response effects
extended exposure times
choice of extract conditions

Question 20

disadvantages of elution

Answer 20

time required for preparation

Question 21

cytotoxicity vs viability

Answer 21

based on physical and/or physiological differences between live and dead cells

Question 22

metabolic assays

Answer 22

based on the conversion of one dye to another in the presence of metabolically active environment
cell number is determined using standard curve
underlying assumption that cells have constant metabolic rate

Question 23

viability assay based on constants that reflect cell number

Answer 23

one can estimate the number of cells by measuring the number of ATP molecules
generally the number of ATP molecule per cell is constant
metabolically active cell converts ADP back into ATP faster compared to dormant cells

Question 24

combining cell number assay and metabolic assay

Answer 24

these two end points don’t measure the same thing
cell number –> measure of cell death (important of acute biocompatibility
metabolic assay –> cell health (slow does not equal death)

Question 25

in vitro model is an excellent tool to determine

Answer 25

lack of biocompatibility

Question 26

in vivo implant models

Answer 26

non-functional test
functional test

Question 27

non-functional in vivo implant models

Answer 27

focus on direct interactions between the substance and chemical and biological nature of implant environment

Question 28

functional test in vivo implant models

Answer 28

functional model that it test the device as intended

Question 29

limitations of in vivo implant models

Answer 29

interspecies variation, local tissue conditions that are abnormal in some species may be chronic in others, infection, variable metabolism, variable lifetimes