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3D printing of LFIA

Table 1. Summary of the differences between material extrusion and vat photopolymerization 3D printing technologies.
Additive manufacturing Materials Speed Average cost of Printing Limitation
technologies materials (kg) resolution
Material extrusion [31,32] Plastic filaments (PLA, ABS, Fast Affordable; $40 Low Support material
ASA, PETG, and nylon)
Vat photo Liquid photopolymers and Slow Average; $100 High Support material and
polymerization [32,33] resins post-curing required
PLA: Polylactic acid; ABS: Acrylonitrile butadiene styrene; ASA: Acrylonitrile styrene acrylate; PETG: Polyethylene terephthalate glycol

A B C

Figure 6. (A) Schematic of the dipping test without the housing cassette. (B) A lateral flow immunoassay (LFIA) showing a negative signal.
(C) A LFIA showing a positive signal.

3.4. Testing of the assembled strip using an in-house developed setup. We showed that the
test cassette could be prototyped to sustain mechanical
LFIA dipstick strips were assembled to be tested with stress applied to it by hand even if it was designed to
commercial SARS-CoV-2 antibodies to simulate positive or
negative tests. Figure 6A shows a schematic of the test without be printed with minimum thickness to reduce material.
the housing cassette. In this setup, if only the control line shows To support the full functional capabilities of the device,
a red signal, then the sample is negative. If both control line and we also demonstrated that bioprinting of the test lines
test line show a red signal, then the sample is positive. Figures with a robotic arm and microfluidic pump was accurate
6B and 6C depict two LFIA strips that were used as a dipstick enough to detect IgG antibodies, when tested with
in our testing. Figure 6B shows a negative sample in which a protein-conjugated AuNP and commercially available
clear band is visible on the control line and no band is visible antibodies.
on the test line. On the other hand, Figure 6C demonstrates a Additive manufacturing technologies can be a great
positive sample containing anti-spike antibodies in which both tool for prototyping and fabricating medical devices and
the test and control lines are visible. diagnostics tools. These technologies can accelerate the
Using a dipstick design in prototyping, the LFIA optimization process by quickly adjusting to the designs
provides a faster way to assess the test and ensure that and then 3D printing the device as needed. During
all the test components are working as desired. When the development phase of a new medical device and
designing a new protein or modifying an existing one to diagnostic tools, 3D printing can provide on-demand
enhance the sensitivity of the test, it is time-efficient to solutions despite the challenges.
test the conjugated material using a dipstick LFIA before
proceeding with further optimization processes to be used Acknowledgments
as a standard LFIA. This work was financially supported by King Abdullah

4. Conclusions University of Science and Technology (KAUST) and
by King Abdulaziz City for Science and Technology
In this study, we demonstrated that the prototyping, (KACST) with a funded grant (4419-KACST COVID
printing, and assembly of an LFIA test are feasible -19).

82 International Journal of Bioprinting (2021)–Volume 7, Issue 4