The synthesis of multithiolated DNA molecules that can be used to produce self-assembled monolayers of single-stranded DNA oligonucleotides on gold substrates is described. Generation 3 polyamidoamine (PAMAM) dendrimers were conjugated to DNA oligomers and functionalized with ~30 protected thiol groups. The protected thiol groups-thioacetate groups-allowed the dendrimer-DNA constructs to be stored in a buffer solution for at least 2 months before deprotection without any observable decrease in their ability to assemble into functional layers. The monolayers formed using these multithiolated DNA probe strands demonstrate target capture efficiencies comparable to those of analogous monolayers assembled with DNA functionalized with single thiol groups. A functional advantage of using dendrimer headgroups is the resistance to probe strand loss in prolonged exposure to buffer solutions at a high temperature (95 °C).

Short sequences of DNA immobilized on gold surfaces can be used to capture an array of target molecules because of their high level of specificity. Depending on the nature of the target molecules, the proper density and distribution of the immobilized DNA molecules are fundamental to the quality of the sensor. With the aim to control the packing density and minimize the heterogeneity of the surfaces, DNA–dendron conjugate molecules were synthesized in solution and used to make self-assembled monolayers of single-stranded DNA surfaces on gold. The headgroups used were polyamido amine dendrons (cleaved cystamine core dendrimers) of generations two through five. The structural composition of these self-assembled monolayers was characterized using grazing angle Fourier-transform infrared and X-ray photoelectron spectroscopies. Surface plasmon resonance was used to measure surface densities of the probe monolayers and each monolayer’s ability to capture fully complementary DNA strands from solution. The surface density of the probe monolayers was found to decrease with increasing dendron generation number, while the hybridization efficiency increased with increasing dendron generation number.