Background: Observational tools have been developed to assess pain in cognitively impaired individuals. It is not known, however, whether these tools are universal enough so that even pain depicted in print art can be assessed reliably. Therefore, the aim of this study was to assess the reliability in scoring facial expressions of pain in dental print art from the 17th, 18th, and 19th century, using a Short Form of the 15-item Pain Assessment in Impaired Cognition (PAIC15-SF) tool. Methods: Seventeen prints of patients undergoing dental procedures were scored twice by two inexperienced observers and an expert and once by a Gold Standard observer. Results: All observers achieved high intra-observer reliability for all four items of the category “facial expressions” and for three items of the category “body movements” (ICC: 0.748–0.991). The remaining two items of the category “body movements”, viz., “rubbing” and “restlessness”, were excluded from further research because it was not possible to calculate a reliable ICC. Overall, the intra-observer reliability of the expert was higher than that of the inexperienced observers. The inter-observer reliability scores varied from poor to excellent (ICC: 0.000–0.970). In comparison to the Gold Standard, the inter-observer reliability of the expert was higher than that of the inexperienced observers. Conclusion: The PAIC15-SF tool is universal enough even to allow reliable assessment of facial expressions of pain depicted in dental print art.

Nanodiamonds (NDs) are carbon nanoparticles with a large refractive index, a high density, and exceptional chemical stability. When excited by green light, they can emit bright red fluorescence from implanted nitrogen-vacancy (NV) centers. Taking advantage of these properties, we have developed antibody-conjugated NDs as in vitro diagnostic sensors for two complementary assays: particle-enhanced turbidimetric immunoassay (PETIA) and spin-enhanced lateral flow immunoassay (SELFIA). To achieve this goal, monocrystalline diamond powders (∼100 nm in diameter) with or without NV implantation were first treated in molten KNO3 to reduce their size and shape inhomogeneity, followed by surface carboxylation in strong oxidative acids and non-covalent conjugation with antibodies in water. PETIA and SELFIA were carried out separately with a microplate reader and a magnetically modulated fluorescence analyzer. Using C-reactive protein (CRP) as the target antigen, we found that anti-CRP-conjugated NDs exhibited high colloidal stability over 1 month at 4 °C in buffer solution. The limits of detection for 3 μL of CRP sample solution were 0.06 μg/mL and 1 ng/mL with variation coefficients of less than 10 and 15% for PETIA and SELFIA, respectively. These two methods together provide a detection range of 1 ng/mL–10 μg/mL, potentially useful for clinical applications. This work represents the first practical use of rounded monocrystalline NDs as in vitro diagnostic reagents.