While developing our nanoplastic detection system, we felt the need (aspired) for a rather unconventional microplate setting. Even though a manually altered microplate was used throughout the iGEM competition, we noticed that there was an absence of a properly designed and ready-to-use solution. Hence, we propose a 3D model for a custom glass microplate with incorporated cellulose membrane. The hardware is a sustainable alternative to plastic microplates.

As the primary goal of the NanoFind system is to detect nanoplastic particles in water samples, plates made from plastic were not an option. Due to the engineered peptides' high affinity for plastic surfaces, false-positive results may be obtained. In addition, the plastic-binding peptides conjugated with a cellulose-binding domain required a cellulose base for envisioned immobilization of the whole detection system. Hence, two key features, glass surface and incorporation of cellulose, were crucial for a feasible testing of our engineered peptide complex.

While performing experiments over the duration of the project, we managed to find a temporary DIY solution - conventional glass-coated plastic plates with addition of manually cut cellulose circles. However, having in mind a proposed project implementation - the nanoplastic detection kit - we created this 3D microplate model.

Most of the biological assays are performed using laboratory plasticware such as pipette tips, microplates, tubes, and etc. Despite the universal application, plastic degradation and leaching of contaminants or impurities from plasticware can have a significant impact on the performed bioassays [1]. As a result, the inertness of glass material could be more favorable over plastic. Yet glassware is still compatible with optical systems and may even outweigh the quality of results compared to the use of plasticware [2].

The proposed hardware contains three parts - a bottom frame of a plate, cellulose sheet, and a top plate with clamps on the sides. The form and size of the microplate matches a standard 96-well plate, yet each detachable part was specifically tailored to aid its function.

Regarding the bottom part of the plate, it is designed as a rectangular glass frame with 96 raised and rounded knobs. The aim was to create such a hardware system that would enable tight installment of the top plate wells onto the knobs on the bottom. Hence, the size of the knobs complement the size of the inner parts of the projected wells.

For the middle part of our custom glass microplate, we are using a sheet of cellulose, which is dedicated to the immobilization of the engineered peptides. The great advantage of this part is that instead of using disposable plates, it allows changing only the sheet itself.

Finally, the last piece to our hardware is the top glass plate incorporating projections of the wells. In addition, two clamps on the sides are tailored to support the tighter assemblance of the framework. As a result, the cellulose membrane is fully squeezed in between two different glass sheets, therefore the bottom parts of the wells are equally covered in cellulose. This resolves the problem of inconsistent sizing of the manually cut cellulose circles.

Our 3D model is a custom glass microplate incorporating a cellulose membrane. The versatility of our proposed microplate originates from the detachable design. Not only could the microplate be used with a cellulose sheet but it could also be exploited using sheets of other materials or as without any incorporated sheets a simple glass plate. The model is universal for liquid-based samples and compatible with the fluorescence measurement methods due to the black frame, which reduces background noise.