Reconditioned microplates and tubes for Pierce BCA protein assay
To assess whether reconditioning affects protein quantification accuracy, we performed the Pierce BCA assay using two formats: a microplate-based method (96-well polystyrene plates) and a tube-based method (1.5 mL polypropylene microcentrifuge tubes).
Three microplates and 18 tubes were subjected to five reconditioning cycles and reused to perform the assay after each cycle, compared against new consumables at every cycle. Both formats followed standard BCA protocols, with 9 concentration standards and a Milli-Q water blank run in each condition. Absorbance was measured at 562 nm, and standard curves were generated for each condition. Blank absorbance, standard curve absorbance, and standard deviations were compared between new and reconditioned consumables to evaluate any effect on measurement accuracy and variability.
For full methodology and detailed results, see our published study: Mansouri et al., 2026 — npj Materials Sustainability
Protein quantification results in 96-well microplates and micro-centrifuge tubes using the BCA assay. Statistical analysis was performed using the Mann–Whitney U test with a Bonferroni-Holm correction. No statistically significant differences were observed. Each standard was tested in five replicates per plates for microplates and in three replicates for tubes (total of 18 tubes).
Results
Reconditioned microplates and tubes produced BCA standard curves comparable to new consumables across all reconditioning cycles. For tubes, R² values were consistently above 0.99 for both new and reconditioned conditions, and no statistically significant differences in absorbance were detected across any of the standards. The blank absorbance of reconditioned tubes was marginally higher than new tubes (by approximately 0.003 absorbance units), but this difference was not statistically significant. For microplates, R² values remained above 0.97 in all conditions, and no statistically significant differences in absorbance were detected across any of the standards.
Effect sizes and standard deviations varied slightly across standards and replicates in both formats but showed no consistent pattern favoring either group, suggesting that observed variation reflects normal experimental factors such as standard preparation, handling, or measurement timing rather than any effect of reconditioning.
These results support the safe reuse of microplates and microcentrifuge tubes for protein quantification, with no loss of accuracy or reliability across five reconditioning cycles.