4. A small spherical bead is used as a controlled drug release capsule in the gastrointestinal system. In the particular case, a 0.1-cm-diameter bead has a uniform initial concentration of 0.2 mmol/L of the drug griseofulvin (species A). Determine the time it will take for the concentration of the griseofulvin at the center of the bead to reach 10% of its initial value. The diffusivity of griseofulvin within the bead material is 1.5 ×10-7 cm²/s. Upon release from the bead, the drug is immediately consumed so that the surface concentration is essentially zero. 5. The diffusion rate of the enzyme ribonuclease into a porous chromatography support was measured at 298 K, and an effective diffusion coefficient of 5.0 x 107 cm2/s was backed out of the data. Estimate the mean pore diameter of the support. The molecular diffusion coefficient of ribonuclease in water is 1.19x106 cm2/s at 298 K, and the diameter of the molecule is 3.6 nm. 3. A "drug patch" is designed to slowly deliver a drug (species A) through the body tissue to an infected zone of tissue beneath the skin. The drug patch consists of a sealed reservoir containing the drug encapsulated within a porous polymer matrix. The patch is implanted just below the skin. A diffusion barrier attached to the bottom surface of the patch sets the surface concentration of the drug in the body tissue at 2.0 mol/m³, which is below the solubility limit. The mean distance from the drug patch to the infected area of tissue is 5 mm. To be effective, the drug concentration must be at least 0.2 mol/m³ at the top edge of the infected zone. a. Determine the time it will take in hours for the drug to begin to be effective for treatment. The effective molecular diffusion coefficient of the drug through the body tissue is 1 x10-6 cm²/s. b. If the effective molecular diffusion coefficient were twice as fast, what would happen to the time it will take for the drug to be effective?
4. A small spherical bead is used as a controlled drug release capsule in the gastrointestinal system. In the particular case, a 0.1-cm-diameter bead has a uniform initial concentration of 0.2 mmol/L of the drug griseofulvin (species A). Determine the time it will take for the concentration of the griseofulvin at the center of the bead to reach 10% of its initial value. The diffusivity of griseofulvin within the bead material is 1.5 ×10-7 cm²/s. Upon release from the bead, the drug is immediately consumed so that the surface concentration is essentially zero. 5. The diffusion rate of the enzyme ribonuclease into a porous chromatography support was measured at 298 K, and an effective diffusion coefficient of 5.0 x 107 cm2/s was backed out of the data. Estimate the mean pore diameter of the support. The molecular diffusion coefficient of ribonuclease in water is 1.19x106 cm2/s at 298 K, and the diameter of the molecule is 3.6 nm. 3. A "drug patch" is designed to slowly deliver a drug (species A) through the body tissue to an infected zone of tissue beneath the skin. The drug patch consists of a sealed reservoir containing the drug encapsulated within a porous polymer matrix. The patch is implanted just below the skin. A diffusion barrier attached to the bottom surface of the patch sets the surface concentration of the drug in the body tissue at 2.0 mol/m³, which is below the solubility limit. The mean distance from the drug patch to the infected area of tissue is 5 mm. To be effective, the drug concentration must be at least 0.2 mol/m³ at the top edge of the infected zone. a. Determine the time it will take in hours for the drug to begin to be effective for treatment. The effective molecular diffusion coefficient of the drug through the body tissue is 1 x10-6 cm²/s. b. If the effective molecular diffusion coefficient were twice as fast, what would happen to the time it will take for the drug to be effective?
Chapter5: Unit, Percentage, Milliequivalent, Ratio, And Household Measures
Section: Chapter Questions
Problem 3.3P
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Transcribed Image Text:4. A small spherical bead is used as a controlled drug release capsule in the gastrointestinal system.
In the particular case, a 0.1-cm-diameter bead has a uniform initial concentration of 0.2 mmol/L
of the drug griseofulvin (species A). Determine the time it will take for the concentration of the
griseofulvin at the center of the bead to reach 10% of its initial value. The diffusivity of griseofulvin
within the bead material is 1.5 ×10-7 cm²/s. Upon release from the bead, the drug is immediately
consumed so that the surface concentration is essentially zero.
5. The diffusion rate of the enzyme ribonuclease into a porous chromatography support was
measured at 298 K, and an effective diffusion coefficient of 5.0 x 107 cm2/s was backed out of the
data. Estimate the mean pore diameter of the support. The molecular diffusion coefficient of
ribonuclease in water is 1.19x106 cm2/s at 298 K, and the diameter of the molecule is 3.6 nm.
Transcribed Image Text:3. A "drug patch" is designed to slowly deliver a drug (species A) through the body tissue to an
infected zone of tissue beneath the skin. The drug patch consists of a sealed reservoir containing
the drug encapsulated within a porous polymer matrix. The patch is implanted just below the skin.
A diffusion barrier attached to the bottom surface of the patch sets the surface concentration of
the drug in the body tissue at 2.0 mol/m³, which is below the solubility limit. The mean distance
from the drug patch to the infected area of tissue is 5 mm. To be effective, the drug concentration
must be at least 0.2 mol/m³ at the top edge of the infected zone.
a. Determine the time it will take in hours for the drug to begin to be effective for treatment.
The effective molecular diffusion coefficient of the drug through the body tissue is 1 x10-6
cm²/s.
b. If the effective molecular diffusion coefficient were twice as fast, what would happen to the
time it will take for the drug to be effective?
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