RESUMEN
Vitamin D is one of the most essential nutrients for brain development, and deficiencies during pregnancy and early childhood development might be associated with autism. Regular monitoring of serum 25-hydroxyvitamin D3 level could help in early diagnosis and therapy. Analytical measurement of serum 25-hydroxyvitamin D3 level using the traditional matrix-matched calibration technique yields inaccurate results due to absence of serum matrix free from 25-hydroxyvitamin D3. The aim of this work was to develop a validated spectrofluorimetric methodology based on the standard addition approach for quantifying 25-hydroxyvitamin D3 levels in real serum samples of autistic children. The spectrofluorimetric methodology utilizes functionalized graphene quantum dots as a fluorescent probe for selective quantification of 25-hydroxyvitamin D3 level, which is based on measuring the quenching properties of 25-hydroxyvitamin D3 on a fluorescent probe. The standard addition approach exhibits a minimal matrix interference since it identically utilizes the same matrix of each study sample for creating its own calibration curve. The method was validated using the guidelines outlined in ICH M10 draft for endogenous compounds quantification. The method was successfully applied for quantifying the serum 25-hydroxyvitamin D3 levels in autistic and healthy children, and autistic children had significantly lower serum 25-hydroxyvitamin D3 levels (with a mean ± SD of 23.80 ± 17.19) when compared to healthy children (with a mean ± SD of 50.13 ± 18.74, P < 0.001). These results suggested an association between vitamin D deficiency and autism.