The Use of Hydroxyapatite for Protein Delivery Systems

Researchers in this article were trying to determine the best design for a drug carrier that would minimize the negative side effects patients face. Since many diseases are caused by proteins, the researchers experimented with the possibility of using hydroxyapatite (HA) as a protein-delivery system. Hydroxyapatite, a biomaterial that can be found in hard tissues, is known for its ability to bind to proteins easily. Thus, the researchers looked at HA’s adsorption and desorption abilities with cytochrome c and insulin. Cationic Cytochrome c was chosen for its ability to start apoptosis in a cell once entering the cell’s cytosol, and anionic insulin was picked for it success in reducing blood sugar levels in patients with diabetes.

In order to test the adsorption and desorption of each protein to HA, the researchers had to calculate the association and dissociation ratios of both proteins. Association ratios were determined by mixing each protein with HA followed by centrifugation, reversed phase high performance liquid chromatography (HPLC), injection of an autosampler, and a linear gradient elution. Dissociation ratios were calculated by taking the HA that had absorbed either protein, centrifuging them, and estimating their concentrations via HPLC.

After experimentation, the researchers made several observations. It was noted that insulin was more efficient in adsorbing to and interacting with HA than cytochrome c. In addition, insulin was observed to be released from HA at a slower rate than cytochrome c and that the release of insulin differed depending on the pH. Based off these observations, the researchers concluded that adsorption and desorption of proteins to HA depend on the size and charge of the protein. Therefore, HA has the potential to be used as a protein-carrier with controlled releases based on the surrounding pH and size of the absorbed protein.

I found this article interesting because it involved biomaterials, which is the track in biomedical engineering I am most interested in. The article also mentioned several ideas that I have learned and used in both chemistry and physiology, so I enjoyed reading about the application of those ideas towards the improvement of today’s medicine.

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