Chitosan gold nanoparticles for detection of amplified nucleic acids isolated from sputum

A platform for nucleic acid detection employing chitosan and chitosan coated gold nanoparticles (AuNPs) was developed. Mycobacterium tuberculosis (MTB) was used as a model target. MTB DNA was extracted from sputum using simple total nucleic acid extraction. Following amplification of MTB DNA, chitosan and AuNPs were added to samples. Free chitosan conjugated non-target DNA in negative samples, avoiding AuNP-DNA interaction and hence negative samples remained red. In positive samples, amplified DNA was capable of saturating free chitosan leading to AuNP aggregation where positive samples turned blue. Via visual color detection 15/16 MTB positive samples and 3/3 negative samples were correctly identified. This test is a 1-tube, 1-step assay reducing the risk of contamination in molecular laboratories and is a proof of concept on how chitosan; a cheap polymer could increase the sensitivity of AuNPs towards specific detection of nucleic acids without using target specific oligotargeters or expensive extraction kits.