Nanoparticles, such as liposome, are commonly used as vehicles for drug delivery to target tissues such as tumors. However, relatively little research has focused on liposomal interactions with the tumor extracellular matrix (ECM), a huge hurdle in the process of perfecting dosage. To our knowledge, there is no method available that allows the observation liposomes against a whole collagen fiber. In order to better study these interactions, we have designed a 3D-printed frame that helps in visualizing liposome transport around a collagen fiber. Observation of our replicated microenvironment will allow us to shed more light on the movements of liposomes within the ECM of tumor cells.
Collagen fiber was removed from adult rat tail and allowed to soak in phosphate-buffered saline (PBS) overnight. Primary design of the frame was done using SketchUp software. Printing of 12mm frame design was done using a Form 2 3D printer (Formlabs). Fiber-in-frame was placed in a glass bottom microwell dish (MatTek Corp.). Research-grade liposomes that mimic the clinical product Doxil (DoxomTM, Liposomics) were used in a background of 0.07mg/ml BSA solution, and added to the channel. Visualization of the interaction was done using confocal microscope (Nikon A1R-MP+ Multiphoton System).
As a proof-of-concept, we mounted a collagen fiber into our frame and filled channel with BSA solution. Observation indicates that liposomes prefer to accumulate on the collagen fiber surface. Multiple trial frames were needed to account for height requirements necessary for confocal microscopy. Our built-in sample well allowed for a maximum 20 uL of formulation to be added into the channel environment from one end of the fiber. Our next steps will focus on reducing height and volume of background and sample needed as well as removing the need for a dish or slide altogether. Future studies will focus on kinetic phenomena in this microenvironment.
Using the methods described above, we observed that Doxom liposomes accumulated near the fiber surface. This suggests that liposomes can use collagen as a route of travel in the extracellular environment. Future experiments with this frame design and others will be used to study the liposomal interactions with collagen and other ECM components. In addition to new frame designs, instruments with higher intensity and resolution will provide more accurate data.||