Biomaterials

Homework 5

Assigned: April 19, 2014
Due: April 29, 2014

1. List any four drug encapsulation methods.
1. Coating technique, also known as the Wurster process, involves coating the drug by air spraying a biodegradable polymer coating on the drug. In order to get a uniform coating, the drug particles are isolated and suspended in a solid or liquid medium before being sprayed on. The amount of polymer that is sprayed on will change the coat’s thickness which will allow the degradation time to be controlled.
2. Coacervation involves separating a colloid material into different immiscible chemical phases. First, the drug is mixed into a solution of the coating polymer. Then the two substances are separated by an emulsion method. There are several emulsion techniques such as applying heat, adding salt, or adding a non-solvent. Then these separated drug particles are coated with a second emulsion method which hardens the outer coating.
3. Co-extrusion is a process in which the polymer shell is pumped concentrically around the drug particle. The drug is individually prepared by an application of air flow, electrostatic separation, or mechanical vibration. This separates the drug into individual “particles” so a syringe pump can wrap the drug with a polymer shell.
4. Spray drying is a common technique that forms drug particles and then dries them very fast. First, the drug solution is atomized into a spray of droplets and then subjected to a hot airstream. The drug droplets rapidly cool down and form the powder capsules we know today.

2. Define Passive and Active Targeting in drug delivery. Discuss their advantages over traditional drug delivery routes for cancer treatment.
The disadvantage of traditional drug delivery is that the drug’s efficacy decreases due to drug degradation as it travels through the body. In compensation, a high dosage is required, but that can lead to toxic side effects.
Passive targeting allows nanoparticles to easily pass through the leaky vasculature of cancer tissue. The drug loaded nanoparticles go into the blood stream, and release its drug payload at the extracellular matrix outside the cancer tissue. The drug then passes through the cancerous membrane and does its job. However, some of the drug may be absorbed by the surrounding healthy tissue which will kill the healthy cells. Active targeting allows nanoparticles to target expressed markers that indicate pathogenic tissue. The nanoparticles will bind to specific receptors and get absorbed into the cancer cells. Then it will release its drug payload. Active targeting will only attack the cancer cells and not the surrounding healthy cells. Therefore, the drug’s effects are localized to a specific area and reduce the side effects of the drug

3. Give one example of blood vessel scaffold design and the rationale behind the design.

A natural polymer graft is composed of collagen and elastin fibers in order to mimic the natural adventitial layers of blood vessels. By using these natural fibers, the material is biocompatible with the body. Smooth muscle cells are mixed with a natural polymer solution and incubated to let the cells integrate with the polymer. The rationale is that by encapsulating the