The effects of temperature treatments on the structure of an injectable depot material consisting of silica microparticles and a silica hydrogel
Nygård, Ida (2022)
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2022032925952
https://urn.fi/URN:NBN:fi-fe2022032925952
Tiivistelmä
During transportation of injectable depot materials, temperature variations might occur as they are shipped globally in different climates. A systematic approach to study the effects of temperature variations was therefore conducted. Furthermore, freezing and thawing cycles were conducted on the depot material to study the effects of repeated freezing. The samples might also be subjected to unwanted deformation at some point in their life cycle, which is why the material was purposely deformed to conduct research on the effects of this action on the material structure.
The objective of this thesis was to prepare these injectable depot materials containing silica microparticles and a silica hydrogel and determine the impact of the temperature treatments on the structure of the material. Depot samples were conditioned in room temperature, fridge, freezer and in a heat chamber. The temperature treatments or the conditioning parameters were chosen based on situations which could arise during transportation of the injectable depots. A so-called Oscillatory-Rotational-Oscillatory (ORO) measurement was also set up to study the ability of the material to recover after deformation. The effects of the temperature treatments were studied by three methods: Firstly, a rheological measurement to evaluate the rheological properties of the depot material after each conditioning, secondly, a manual injectability study, which gave a qualitative insight into the structure and behavior of the material upon injection after conditioning and, lastly, an injection force measurement, which measured the load (N) or the force (N) that was required for the material to be injected through the needle.
The results suggest that temperature has an effect on the material structure and quality. The rheological measurements showed varied results but gave an overall indication of the material properties before and after conditioning. The manual injectability study suggested that the samples conditioned in the freezer lost some of the desired properties. The silica gel-network structure was most severely impacted by the freezing conditions compared to the other conditions. From the injection force measurement, it was also determined that the freezer samples, generally, caused the most clogs or unevenness in injection force. Two freezing and thawing cycles did not impact the structure significantly.
The objective of this thesis was to prepare these injectable depot materials containing silica microparticles and a silica hydrogel and determine the impact of the temperature treatments on the structure of the material. Depot samples were conditioned in room temperature, fridge, freezer and in a heat chamber. The temperature treatments or the conditioning parameters were chosen based on situations which could arise during transportation of the injectable depots. A so-called Oscillatory-Rotational-Oscillatory (ORO) measurement was also set up to study the ability of the material to recover after deformation. The effects of the temperature treatments were studied by three methods: Firstly, a rheological measurement to evaluate the rheological properties of the depot material after each conditioning, secondly, a manual injectability study, which gave a qualitative insight into the structure and behavior of the material upon injection after conditioning and, lastly, an injection force measurement, which measured the load (N) or the force (N) that was required for the material to be injected through the needle.
The results suggest that temperature has an effect on the material structure and quality. The rheological measurements showed varied results but gave an overall indication of the material properties before and after conditioning. The manual injectability study suggested that the samples conditioned in the freezer lost some of the desired properties. The silica gel-network structure was most severely impacted by the freezing conditions compared to the other conditions. From the injection force measurement, it was also determined that the freezer samples, generally, caused the most clogs or unevenness in injection force. Two freezing and thawing cycles did not impact the structure significantly.