Towards HIV Detection: Novel Poly(propylene imine) Dendrimer-Streptavidin Platform for Electrochemical DNA and gp120 Aptamer Biosensors

摘要

The detection of sequence specific DNA and HIV glycoprotein 120 (gp120) based on novelgeneration 4 poly(propylene imine) dendrimer/streptavidin platform is reported. The platform wasprepared by the electrodeposition of the dendrimer on a carbon electrode followed by drop coatingwith streptavidin. The generation 4 poly(propylene imine) dendrimer/streptavidin platform wascharacterised using scanning electron microscopy, voltammetry and electrochemical impedancespectroscopy (EIS). Electrochemical measurements indicated that the platform was stable, conductingand exhibited reversible electrochemistry at a former potential of 140 mV in pH 7.5 phosphate buffer3-/4- saline solution (PBS), while EIS interrogation using [Fe(CN)6 ] redox probe showed a markedreduction in charge transfer resistance (Rct) after modification. The biosensor was prepared by theimmobilisation of single stranded 5'- biotynilated probe DNA and B40 aptamer on the modifiedelectrode and then used to detect complementary DNA and gp120 respectively. The biosensorresponses were evaluated with square wave voltammetry (SWV) and EIS in the presence of PBS and3-/4- -12 2 Fe(CN)6 redox probe. A detection limit of 3.44 x 10 M (S/N = 3) and linearity r = 0.9985 wereobtained for the DNA biosensor while the aptamer biosensor detected gp120 in the nanomolarconcentration range. The DNA biosensor also showed excellent selectivity in the presence of noncomplementary and mismatch DNA strands.