We manufacture our MBA™s using our GEM™ technology; both our arrays and method of manufacture are protected by a number of issued patents (US8,753,880, US9,346,197, and US9,457,497) as well as an expanding set of ongoing applications. We currently make post-prototype GEN1 MBA™s at a modest production scale.
To briefly summarize our GEM™ manufacturing process we use a patterned mold (A) as a template which we overlay with a polymer (PDMS) layer (B); we then heat this stack in an oven to let air bubbles rise into the polymer layer from the pits in the template to form the array of microbubbles (C). After curing we remove the MBA™ so-formed for further processing or immediate use, depending on the application.
We have considerable control over the GEM™ process, which allows us to produce microbubbles of different sizes (biggest diameter and mouth diameter), mouth shapes (which may be varied by changing the shape of the mouth of the pit) and array size and microbubble spacing across the array. See, e.g., Giang UB, Lee D, King MR, DeLouise LA. “Microfabrication of cavities in polydimethylsiloxane using DRIE silicon molds.” Lab on a chip. 2007 Dec; 7(12):1660-2. Epub 2007 Oct 12.
Although we make microbubbles in a variety of sizes and mouth configurations, for typical applications we fabricate microbubbles with a 60 uM mouth diameter and a largest internal diameter of 160 uM. These dimensions result in a bubble volume of about 1 nL, which is an appropriate size for cell growth and other applications of our technology. Note that we produce MBA™s with different microbubble densities; in our typical fabrication an array the size of a microscope slide has about 70,000 microbubbles.
MBA™ Fluid Circulation & Material Retention Properties
Our GEM™ manufacturing process is an elegant and efficient way of producing large arrays of microbubbles for, e.g., repetitive reaction chambers or other repetitive well applications. However bubble-shaped wells have unique properties of fluid flow as compared to traditional cylindrical wells, and Nidus explicitly leverages these properties to obtain superior performance in multiple application areas.
The figure is reproduced from a recent publication by our co-founder Lisa DeLouise with her collaborator Dr. Michael King that shows fluid flow within and over a microbubble (Agastin S, Giang UB, Geng Y, Delouise LA, King MR. “Continuously perfused microbubble array for 3D tumor spheroid model.” Biomicrofluidics. 2011 Jun; 5(2):24110. Epub 2011 Jun 03). Panels (a) and (b) show fluid flow in a circular path within a microbubble, i.e., a flow which allows bubble contents to circulate largely without being lost to the surround. Panels (c) and (d) show flow velocity above and within a bubble, with red a high flow and blue a low flow. These panels further demonstrate how bubble contents are largely retained in our MBA™ products.
Example Application — Tumor Spheroid Formation in MBA™s
As we discuss elsewhere there are a large number of applications that Nidus targets that benefit from this unique fluid-flow property and microbubble content retention. One example from the same publication is shown below, specifically, the formation by a colon cancer cell line (Colo205) of tumor spheroids in the microbubble environment:
These multi-cellular tumor spheroids have been established by multiple researchers as a relevant tumor model for drug testing in cancer research; our MBA™ system provides a particularly simple and effective system for growing and manipulating such tumor spheroids and, as a result, has high potential for cancer research and commercial cancer cell testing and analysis. For more information, see, e.g., Chandrasekaran S, King MR (2012), “Gather Round: In Vitro Tumor Spheroids as Improved Models of In Vivo Tumors,” J Bioengineer & Biomedical Sci 2:e109.
Nidus wishes to thank Dr. Michael King for his permission to reproduce two figures from Agastin S, Giang UB, Geng Y, Delouise LA, King MR. “Continuously perfused microbubble array for 3D tumor spheroid model.” Biomicrofluidics. 2011 Jun; 5(2):24110. Epub 2011 Jun 03. All other figures reproduced by permission.