A. Barchanski
D. Funk
C. L. Sajti
B. N. Chichkov

Carbon nanotubes functionalized with laser-generated gold nanobioconjugates for application as hybrid nanosensors

Conference on Advanced Nanoparticle Generation and Excitation by Lasers in Liquids (ANGEL)
9.-12. Mai
Type: Konferenzbeitrag
Carbon nanotubes (CNTs) may be applied as novel class of nanowires, due to their remarkable electrical, optical mechanical and thermal properties. Especially their functionalization with biomolecules such as proteins and DNA has attracted considerable interest for the development of biosensors, e.g. immunosensors. Fabrication of such sensor systems is not trivial, as the perfect graphitic structure of CNTs is destroyed by covalent surface functionalization, resulting in a modification of the physical properties. As non-destructive alternative, the non-covalent functionalization of CNTs with DNA was investigated and is described elsewhere. However, a helical wrapping of the nucleotides around the CNT walls was discovered, which might reduce the functionality of the nanosensor. Here, we present the efficient, non-covalent functionalization of CNTs with laser-generated gold nanoparticles (AuNPs) and gold nanobioconjugates (Figure 1, left panel) in a single-step process. A CNT loading up to 45 \% was reached with ligand-free AuNPs (Figure 2, right panel), indicating a high affinity of the partially oxidized gold surface towards the CNTs. Furthermore, biomolecules, such as single-stranded DNA (ssDNA) and bovine serum albumin (BSA) were applied for the direct attachment and CNT loadings of 2 - 20 \% for ssDNA and between 1- 9 \% for BSA were determined (Figure 2, right panel). If the biomolecules were conjugated to laser-generated nanoparticles by the method of in situ-conjugation, a mean number of 54 ssDNA molecules and 96 BSA molecules per nanoparticle were calculated. CNT loadings of 9 – 45 \% for AuNP-ssDNA nanobioconjugates and 8 – 41 \% for AuNP-BSA nanobioconjugates were reached (Figure 2, right panel), which yield in a tremendously increased amount of biomolecules per CNT compared to the direct biomolecule conjugation route. Moreover, the resulting hybrids were pH- and ionic strength-independent, indicating weak physical interactions, such as van der Waals and hydrophobic forces. In order to demonstrate exact orientation of biomolecules and thus functionality of hybrid nanosensors, biological immunoassays are performed. In summary, the non-covalent functionalization of CNTs with laser-generated gold nanoparticles and gold nanobiohybrids is a novel, promising route for hybrid nanosensor fabrication.