Background: Currently, there are no preclinical models capable of studying pharmacoethnicity differences of drugs. Hence, health disparities are found with retrospective studies only. The absence of an in-vitro model that studies pharmacoethnicity differences result in negative outcomes for minorities. On the other hand, in-vitro testing with human tissue may enable pharmacoethnicity differences to be identified prior to clinical trials. Here we present a microfluidic in-vitro platform, which uses human biopsies, to determine drug penetration of nano-carriers and drugs. The objective of this project is to design and evaluate a microfluidic in-vitro platform to test Doxil-like liposomes in breast cancer tumors of African American and Whites to compare drug penetration in tissue based on blood and interstitial fluid.
Method: The microfluidic platform is design based on the shape and location of the available tumor section. Current capillary model includes etching capillary channels at 120 µm diameter with an estimated precision ± 10 µm, channel spacing is set to 300 µm. Currently we have built one microfluidic chip on tumor device using two 15 µm sections of breast cancer tumor sample (CHAU5APK).
Capillary channels are etched in glass slides using a 5W UV Laser with 70 mm f-theta lens, at a pulse rate of ≤ 15 ns. Glass etching parameters are pass 1, 100 mm/s, 40kHz, 20 µs q-pulse width; pass 2, 200 mm/s, 100 kHz, 8 µs q-pulse width. A total of 3 glass slides are etched, one for interstitial fluid flow, one for blood fluid flow, and finally the tumor slide with capillary channels etched in the tumor to present the desired drug. Afterwards, micro via channels are drilled using the UV system and revised if necessary, using sub-millimeter drill bits. Finally, a fourth slide is etched with four 1/16 diameter holes and it is used as the interface between the tumor chip and the chromatography tubing used to load desired drug and solutions.
Results: The first proof of concept prototype has been successfully built. The initial prototype demonstrated tumor tissue was stained by an acridine orange solution by a total of up to 75 µm past the capillary channels, after a 10 minutes exposure. Tissue exhibited a quick initial dye uptake followed by a slower uptake of 2.5 µm/mn. Due to current assembly limitations, interstitial fluid pressure was merged with blood vacuum pressure side.
Conclusion: Method to construct microfluidic chip on tumor devices is nearing completion. Initial proof of concept prototype establishes chamber-tissue distance to be adequate for further studies and will not require redesign. Minor method development is pending to improve assembly of chip to prevent capillary channels from getting plugged during assembly. A successful outcome of this research will permit measuring drug uptake of breast cancer tumors based on race and other attributes. The microfluidic platform is expected to have a positive impact by providing with a methodology that can evaluate pharmacological differences during in-vitro drug development and reduce the preclinical-clinical gap caused by pharmacoethnicity differences.
