Download Q: Write a one- to two-sentence description of a matrix drug

Q: Write a one- to two-sentence description of a matrix drug-delivery system and a reservoir drugdelivery system. Use a diagram, if that is helpful.
So what are the defining features of a reservoir drug-delivery system? Literally, the system has a
reservoir – aka, a chamber-like component that houses the drug usually in liquid form. This “core” of the
drug is surrounded/encased in a film made of certain types of polymer – usually biocompatible. The
chemical characteristics of the polymer (such as the molecular composition of the polymer – if it’s a
pretty densely branched repeating chain of molecules ( that is essentially what a polymer is) vs. a less
branched chain of repeating molecular chain) and the physical properties of the polymer (such as how
thick vs. thin the film is) can affect the rate of the drug within being released through the polymer
coating of the reservoir. The physical / chemical properties of the drug molecules that would interact
with the physical / chemical properties of the encasing polymer membrane can influence the rate of the
drug diffusing through the membrane out of the reservoir and into the external environment. The path
that the drug molecule takes is: dissolution of drug from the core into the surrounding polymer 
diffusion of the drug across the polymer membrane  dissolution of drug into the external
environment.
So what’s a matrix drug-delivery system like? This type of drug-delivery system also utilizes polymers but
in a different way: the polymer doesn’t serve as an enclosing membrane to the drug core, but the
polymer – usually biocompatible so that it can be placed directly in the vicinity of the target region in the
body - is actually the ‘chunk’ in which drug molecules are evenly dispersed/dissolved throughout the
chunk. And when the matrix delivery system – aka the ‘chunk’ of polymer that contains drug molecules
dispersed through it – is placed near the target region for, there
A question that you may want to ask yourself is … what is the difference between a matrix drug-delivery
system vs. a reservoir drug-delivery system? What do you think? Hint: A noted limitation of the reservoir
system is that drug molecules with large molecular weights or proteins (molecules with very high
molecular weights!) may have more difficulty in dissolving into the surrounding polymer and in diffusing
across through the enclosing polymer membrane. In such cases the matrix system is sometimes better
because it allows the drug molecules and/or proteins already dissolved and dispersed throughout the
polymer itself from the get-go, requiring only for drug to diffuse through the polymer to the external
environment.
Q: You are asked to design a delivery system that provides a constant rate of release of insulin. You
want the system to release 1 mg of insulin per day. Will you use a matrix or a reservoir system? Make
a list of the advantages and disadvantages of each design for this particular application.
So let’s see here… from the question you glean that the desired rate of insulin release is a constant 1 mg
per day. Which of the two: matrix OR reservoir system allows for a constant drug-release profile as a
function of time? (by the way/for your edification: whenever you see the phrase “A as a function of B”
that means that the A is the y-axis (dependent variable) and B is the x-axis (independent variable))
Regarding drug delivery rates, which of the two do you think will produce a relatively more constant rate
of drug release at steady-state? Hint: In the reservoir system, there is drug from the core that is in
contact with the enclosing membrane trying to make it to the outside. And assuming for a good bit of
time that the drug reservoir level is sufficient, there will be a steady rate of drug dissolving into the
surrounding polymer, diffusing across the membrane, and emanating out into the target region. Think
about the matrix system. Drug molecules close to the outside of the polymer chunk will seep out first
(they have the shortest route to the external environment). But what do you think happens to the rate
of drug release as time increases? (Think about the molecules that are diffusing out, but are situated
more in the center of the polymer chunk – it would take more time for such molecules to diffuse out
into the external environment) Now think about graphing both drug release profiles as functions of time
(aka time on the x axis). Which do you think would have a more constant rate of drug release?
Also as you can imagine, in general, let’s think about the structural complexity and/or simplicity of a
matrix vs. reservoir system. Which one do you think is more structurally complex? Do you think that
from a manufacturing standpoint, perhaps one that is more structurally complex would be more
expensive and thus a disadvantage especially in producing mass quantities? Hint: think which one would
have more parts to assemble (reservoir + enclosing membrane vs. mass of polymer with drug already
dissolved in it)
Q: You are asked to design a delivery system for local treatment of breast cancer; the system will be
implanted at the site of the solid tumor and slowly release chemotherapy to the local tissue. Will you
use a degradable or a non-degradable polymer? Will you use a matrix system or microspheres? Make
a list of the advantages and disadvantages of each for this particular application.
One point to consider about nondegradable polymers is that they are more robust and could be used for
long-term drug release - possibly appropriate for long-term therapies for such as breast cancer, one
drawback may be that it is more difficult to achieve a steady/constant drug release rate with
nondegradable-polymer based matrix systems.
We know that if a non-degradable polymer-based delivery system is implanted to local tissue, it would
have to be surgically removed from the region at the end of therapy right (where as a degradable
polymer (that is biocompatible of course!) would eventually dissolve into local tissue). So with the
intention of maximizing greatest comfort and quality of life to the patient – (which is the foundational
motivation behind the innovation and work in BME, right?), would a degradable or non-degradable
polymer-based system be more ideal?
If implanted to the site of the solid tumor – aka in vivo or in the body, and we want to go with a
degradable polymer, one cannot emphasize enough maintaining the patients’ safety throughout
treatment. It’s perhaps important to note how controllably the polymer will degrade in vivo and
whether it would dissolve into inert/non-toxic constituents.
In a biodegradable matrix, the parameters of the degradation (usually by hydrolysis, or sometimes autocatalyzed hydrolysis) may be able to be ‘tuned’ such that the rate of drug delivery can be controlled by
the erosion kinetics.
Microspheres could potentially be used, however, they are more so delivered to the target site via
injection or ingestion. Because microspheres can be injected to a site (and thus delivered with high
precision to the desired location), perhaps they can be used more ideally for introducing these drug
delivery systems to the actual tumor itself by injecting the spheres into the tumor.
For slow release to the local tissue, however, perhaps a matrix system made of a biodegradable polymer
would be more ideal.