• lab-on-a-chip
• biosensori
• funzionalizzazione
• design of experiments
• surface acoustic wave

Traumatic brain injury (TBI) is recognized as one of the principal global causes of acquired disability. Currently, the primary approach to its detection involves the use of expensive and invasive strategies that have a significant impact on the national health system. After a TBI, damaged brain cells release different proteins into the extracellular environment. These proteins can enter the bloodstream by crossing the compromised blood-brain barrier (BBB) due to the traumatic injury. One protein of particular interest is glial fibrillary acid protein (GFAP), which is a type III intermediate filament protein mainly expressed by astrocytes. An increase in its plasma levels correlates with traumatic damage to central nervous systems (SNC). The development of cost-effective and rapid point-of-care (PoC) systems able to detect the presence of TBI biomarkers represents an advantageous strategy to ensure early diagnosis.
Here, surface acoustic wave (SAW) biosensors were used to detect glial-fibrillary-acidic protein (GFAP), one of the most important TBI biomarkers, in phosphate-buffered saline (PBS) using two different approaches to functionalization. Both detection strategies are based on antibodies: the first is based on antibody-splitting and direct surface immobilization for enhancing surface coverage and orientation, the second on an 11-mercaptoundecanoic acid (11MCA) linker and an 11-mercaptoundecanoic alcohol (11MA) spacer for enhancing specificity.
The effectiveness of these functionalization strategies depends on various factors, such as the chemical properties and interactions between the molecules involved in the process. Therefore, the Design of Experiments (DoE) tool was applied to obtain enough knowledge about the parameters that significantly influence the process. This information was used to identify the optimal conditions for each functionalization strategy.
Then, a signal amplification strategy based on gold nanoparticles conjugated with antibodies was employed to improve the sensitivity and specificity of the detection strategy. The bioconjugation used noncovalent modes of binding based on a combination of electrostatic and hydrophobic interactions between the antibody and the gold surface.
Different nanoparticle sizes (from 5 nm to 400 nm) were evaluated to identify the optimal size that allowed both minimal electrostatic interference with gold surface of SAW biosensors and suitable antibody coverage.