**4. Conclusions**

It can be concluded from the above study that the particle size of AuNPs has no effect on the test zone band intensity of Malaria Pan rapid diagnostic test kits if optical density of AuNP–protein conjugate is adjusted at 520 nm. The test zone band intensity was also observed to be maximum at 520 nm and optical density 3.0. It was found from the study that any quantity of protein can be utilized for AuNP conjugation, if the final optical density (OD) is adjusted correctly. It can also be

concluded that, by optimizing the optical density, an enhanced test zone band intensity can be obtained while reducing the total number of trial and wastage of reagents.

**Author Contributions:** Conceptualization: P.M. and D.N.K.; Methodology: R.N and A.S.; Validation: A.K., J.D.S. and R.K.; Formal Analysis: A.F.V.L.; Investigation: S.J.B.F.; Data Curation: N.S.; Writing—Original Draft Preparation: P.M., R.N. and A.S.; Writing—Review and Editing: A.K.; Visualization: P.P.; Funding acquisition: D.O.B., S.K.P. and P.V.; Supervision: D.N.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
