Last Friday afternoon (11/18), the team met up to test a 300 um-diameter needle coated in BSA for channel formation. We first made up 0.5% agarose and loaded it into the chamber with the needle inside. After the gel solidified, the needle was removed carefully using tweezers. We first tried pushing fluid through with a 20 uL pipette. The fluid chose to pass through the space where the gel met the chamber wall instead of through the channel itself. This led us to believe that 300 um may be too small and confer too much resistance to allow fluid to pass. In addition, we were not able to see if the needle removal left a channel that was able to support itself due to the very small diameter. In future experiments, we will test larger diameter needles and use a dye to track fluid flow through the channel.
On 11/22, I met with Nick Thompson to discuss modifications to the chamber design. We discussed printing a channel out of PLGA or PCL to solve the channel instability issue. However, there were significant limitations with the low permeability and cost of such a channel. We also discussed the possibility of a needle with small enough perforations to inhibit the PEG to flow into the chamber. Pictures and video from our 11/18 experiment are uploaded to the following folder: https://drive.google.com/drive/folders/0Bz1SvoM7LVxSQ09FNlBrLWZVcDQ?usp=sharing
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At the meeting last Friday afternoon with our client on 11/11, we discussed the material properties of our gel chamber and decided to look further into whether or not the materials we wanted to 3D print with would absorb small molecules like urea which is 60 daltons (very small). We also discussed methods to sterilize the device as the autoclave is not an option for most 3D print materials. The high temperatures and pressure that that the autoclave goes up to will end up deforming most 3D print materials that we use.
In our meeting, we also discussed other options to look into. Due to design and print difficulties, our group has decided to try out needles using agarose gel as a proof of concept. From speaking to other researchers in the George Lab who have expertise in using needles that interact with ECM and PDMS gel interfaces, we have decided to submerge our needles in bovine serium albumin (BSA) for 30 minutes in an attempt to decrease the friction coefficient and make it much easier to remove from the gel. An official protocol will be uploaded next week after further discussions with George Lab members. We have also asked for scientific literature and protocols from the lab, which we are in the process of getting. Further, we will be testing the BSA needles in an agarose gel in order to assess the plausibility of this strategy. The needle will be inserted into agarose gels at varying concentrations, allowed to polymerize, and then removed to assess any damage that is done to the gel afterwards. Protocols will be uploaded as these experimental designs are finalized. We are excited to start testing out different components in order to assess the feasibility of our ideas. At the same time, we are also developing back-up plans in case aspects of this prove to be beyond our capabilities. Moving on from slight design modifications of testing chamber lid sealing that were made last week, we the team continued our discussion with Young Guang (client Graduate student) and Nick Thompson at 3D-printing center on medical campus, to actualize the product chamber for rst time (Detailed changes can be observed in the attached images. Circular pegs have replaced the “n” interface between the main body of the chamber and the lid for better leakage prevention.) On this Monday, the rst prototype of the drug-testing chamber was 3D printed. The actual product is presented in images attached, with keys for size comparison. The injection port was eventually not integrated into lid by printing, as our team still needs to assess the practicality of the dimensions of the main chamber. The purpose of this print will be to assess “workability” of the chamber, namely, if the design will be conducive to human manipulation, channel implementation, and gel loading. Our group still plans on exploring carbohydrate glass and are in the process of designing a mold for the sacrificial channel. Due to the fact that our scheduled meeting this week with our client Young Guang (client Graduate student) shall occur on Friday afternoon, this report contains information known and discussed within design team until Thursday. The meeting shall be dedicated to rst experiment design for qualitative testing for the 3D printed chamber prototype—corresponding results of the experimentation will be included in next weekly report.
Most of the progress this week has been focused on chamber design. As such, most of this report will focus on proposed revisions to the preliminary design. These changes can be observed in the attached images.
The “fin” interface between the main body of the chamber and the lid has been replaced by circular pegs. From tests conducted by Dr. Setton’s summer students, the “fin” interface was prone to leakage and warping after multiple uses. The injection port is still absent from the top, as our team still needs to assess the practicality of the dimensions of the main chamber. We are currently scheduling a printing session next week with Nick Thompson to print this design. The purpose of this print will be to assess “workability” of the chamber, i.e if the design will be conducive to human manipulation, channel implementation, and gel loading. Our group still plans on exploring carbohydrate glass and are in the process of designing a mold for the sacrificial channel. However, most of our energy now is dedicated to fleshing out the main chamber design. We have also invited Dr. Yin to our SciNote team (LiSunTao) and project (SettonDrugDeliveryWork). |
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April 2017
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