A freeze dryer for cryogel fabrication and 3D scaffold development

Project Title: A freeze dryer for cryogel fabrication and 3D scaffold development (CPB 419/519 & CPB 471/472)

Project Lead: Amy Yousefi

Email: yousefiam@MiamiOH.edu

Phone: (513) 529-0766

Affiliation: CEC

Project Details: Providing hands-on experience in undergraduate labs and offering experiential learning to students through independent studies and senior capstone projects are key elements of undergraduate education. We currently have about 400 undergraduate students at the Department of Chemical, Paper and Biomedical Engineering (CPB). On average, 40 students take the biomaterials course each spring (CPB 519/519, 3 credit hours). This is a core course required for the bioengineering major. In this course, students are asked to use the freeze-thaw technique to fabricate hydrogels (cryogels) as potential candidates for soft-tissue replacement (lab experiment). The produced cryogels can also serve as soft tissue phantoms, enabling to uncover potential weaknesses in medical imaging systems (brain and liver elastography). These gels are made of hydrophilic polymers, such as poly(vinyl alcohol) (PVA), and need to be characterized in wet and dry states to quantify their water uptake. A freeze-dryer has been requested in this Tech Fee proposal for hydrogel characterization. This equipment can also serve CPB's senior design projects (CPB 471/472). In the past 5 years, my lab has served over 30 CPB students who have worked on the development of 3D scaffolds for tissue engineering. It is essential to properly dry the produced scaffolds after extracting their water-soluble components. A freeze dryer will also greatly contribute to independent studies (CPB 277/377), Undergraduate Summer Scholar projects (CPB 340U), and graduate MS theses (CPB 700).

Problem Project Attempts to Solve: When offering labs to undergraduate students, the quality of equipment we use in our labs directly affect the learning outcomes, via meaningful interpretation of collected data. In 2015, students waited a week before they can measure the weight of completely dried cryogels. This is inconvenient due to the risk of lost/mixed-up samples in CPB's instructional labs that serve over 100 students each year. A freeze-dryer can speed up the drying process, eliminate the risk of bacterial build up, and thereby improve the accuracy of the generated results. The CPB department also offers research opportunities for undergraduate students, either as independent study (CPB 277/377) or in the context of the required senior design projects (CPB 471/472). Therefore, these students will also have access to the equipment. Graduate theses (CPB 700) will equally benefit from this freeze dryer.

Does this project focus on Graduate Studies?: No

Does it meet tech fee criteria?: The details of the educational outcomes are listed under the following question (Biomaterials Lab). The equipment will also be used for senior design projects and independent studies. Figure 1 (attachment) shows the scaffolds that we have fabricated in the lab. The channels are generated after extracting poly(ethylene glycol) (PEG) in water. The PEG construct is produced by additive manufacturing (3D-Bioplotter), then immersed in a polymer solution, subjected to thermallyinduced phase separation, and eventually extracted by water. Freeze drying would be the final step for removing water from these scaffolds. This would add a set of pores that could make the scaffold hierarchical. Micro-, macro- and nano-pores contribute to cell attachment and growth in different ways (bone tissue engineering).

How will you assess the project?: Figure 2 (attachment) shows some cryogels produced by the freezethaw technique. The material used for producing these gels is an aqueous solution of PVA. Here are the steps that students will follow:

  • PVA (1 gr) and DI water (20 ml) will be mixed, sonicated and heated at 85°C on a hot-plate/stirrer.
  • The prepared solution will be poured into aluminum molds (20-mm diameter).
  • The set-up will be placed inside a lab freezer at -20°C.
  • The samples will be removed from the freezer after 24 hour.
  • One wet sample will be weighed after removing from the freezer (Mi) and left to air dry.
  • Another wet sample will be weighed after removing from the freezer (Mi) and placed in freeze dryer.
  • The dried samples will be weighed after the drying is complete (to measure M0).
  • Another wet sample will be weighed after removing from the freezer (Mi) and immersed in DI water.
  • The water-swollen sample will be weighed after 24 hours, 4 days and 7 days (to measure Mt, see below) after dabbing the surface water with a filter paper.
  • The original water content of the cryogels will be calculated as follows: WC (%) = [100 × (Mi - M0) / Mi]
  • The water uptake (swelling) for different time points will be calculated as follows: WU (%) = [100 × (Mt - Mi) / Mi]
  • Once the team reports were submitted (part I), the collected data by all teams will be uploaded to Google Drive to allow students perform statistical analysis (mean and standard deviation).
  • Reproducibility of the data for the air-dried samples and those dried inside the freeze dryer will be compared (part II of the lab report).

Have you received tech fee funding in the past?: Yes

What results were achieved?: (a) A Tech Fee award ($1,123) in 2014 enabled us to purchase some accessories for a diffusion cell designed by Miami's Instrumentation. A Tech Fee report was submitted in 2014. The equipment was intended for a Bioengineering Lab. Data acquisition using LabView software was also performed in 2014. (b) A Tech Fee award ($6,259) in 2015 was used to order one floating network license (FNL) of Comsol Multiphysics as well as one optimization license of the software. A Tech Fee report was submitted in 2016. The software was made available on the Redhawk compute cluster to all Miami faculty and students. An undergraduate student (CPB 340U, USS award) spent the summer of 2015 on 3D scaffold design using Comsol optimization software on Redhawk (384 CPU hours) and additive manufacturing (3D Bioplotter). Also, a graduate student (CPB 700) used 2,367 CPU hours on Redhawk to design hybrid bone-mimicking scaffolds. (c) A Tech Fee award ($1,700, Graduate) in 2015 allowed purchasing a design optimization tool (Abaqus-ATOM) for graduate students and senior capstone projects. The Tech Fee report was submitted in 2016. One floating network license (FNL) of the software was made available on the Redhawk cluster to all Miami faculty and students. The purpose of the module was to enable topology optimization, a method often used to design components with efficient material layout given a certain performance goal such as optimal mechanical strength. The results of the Comsol Optimization (b) are being compared with the output of Abaqus-ATOM software (c).

Did you submit a final report?: Yes

What happens to this project in year two?: No costly maintenance is anticipated for this lab equipment. The expected life-time is usually reasonable, and the Instrumentation Lab (75 Hughes) is well equipped to support any required maintenance.

Hardware: Freeze Dryer and a pump (Labconco) - https://www.fishersci.ca/productDetails_3032491 (similar model), $11,261

Other, please explain: Accessories, $2,573

Total Budget: $13,834