1 SCIENTIFIC REPORTS | (2018) 8:15593 | DOI:10.1038/s41598-018-32756-w www.nature.com/scientificreports A genosensor for detection of HTLV-I based on photoluminescence quenching of fuorescent carbon dots in presence of iron magnetic nanoparticle- capped Au Mohadeseh Zarei-Ghobadi 1,2 , Sayed-Hamidreza Mozhgani 3,4 , Fariba Dashtestani 1 , Amir Yadegari 5 , Fatemeh Hakimian 1 , Mehdi Norouzi 2,4 & Hedayatollah Ghourchian 1 Carbon dots and Fe 3 O 4 @Au were synthesized to develop a new biosensor to detect DNA target. We investigated the photoluminescence property of carbon dots (CDs) in the presence of Fe 3 O 4 -capped Au (Fe 3 O 4 @Au). Firstly, we designed two dedicated probes for unique long sequence region of human T-lymphotropic virus type 1 genome. One of the probes was covalently bound to the CDs. In the absence of target, CDs-probe was adsorbed on the surface of Fe 3 O 4 @Au through two possible mechanisms, leading to quenching the fuorescence emission of CDs. The fuorescence emission of CDs was recovered in the presence of target since double-stranded DNA cannot adsorb on the Fe 3 O 4 @Au. Also, Fe 3 O 4 @Au can adsorb the unhybridized oligonucleotides and improves the accuracy of detection. The specifcity of the proposed biosensor was confrmed by BLAST search and assessed by exposing the biosensor to other virus targets. The experimental detection limit of the biosensor was below 10 nM with linear range from 10 to 320 nM. Nanomaterial-based detection methods have been developed to open novel and simple routes toward improving point-of-care diagnoses 1,2 . One of the main challenges to reach this achievement is utilizing simple methods and environmentally-friendly materials. Carbon nanostructures are known as benefcial biomaterials due to their optical and electrochemical characterizations 3 . Moreover, it has been reported that functionalization of carbon nanostructures with biomolecules can signifcantly ameliorate their performance. Terefore, carbon nanostruc- tures have extensively employed in various biomedical applications including biosensors, drug and gene delivery systems, bioimaging, and tissue scafold reinforcement 3,4 . In the recent decades, biosensors have attracted numerous attentions in pathogen diagnosis, disease progres- sion, point-of-care monitoring of treatment, and drug discovery 5 . Diferent techniques accompany with using signal amplifcation labels have been used to develop the selective and sensitive biosensors. Among them, biosen- sors relying on the fuorescence emission measurement and hybridization between target DNA and labelled probe oligonucleotides facilitate rapid and sensitive detection of biomolecules. Although, organic fuorophores have good features of photostability and high efciency, they sufer from high cost and photobleaching efect 6,7 . One of the proper substitution to the traditional fuorophores is quantum dot nanoparticles (QDs) due to their unique traits, like high quantum yields and photostability, broad excitation, narrow emission, and excellent resonance 1 Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran. 2 Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. 3 Department of Microbiology, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran. 4 Research Center for Clinical Virology, Tehran University of Medical Sciences, Tehran, Iran. 5 Department of Developmental Sciences, Marquette University School of Dentistry, Milwaukee, WI, 53233, USA. Correspondence and requests for materials should be addressed to H.G. (email: ghourchian@ut.ac.ir) Received: 18 May 2018 Accepted: 10 September 2018 Published: xx xx xxxx OPEN