Three-dimensional (3D) plasmonic hot spots for label-free sensing and effective photothermal killing of multiple drug resistant superbugs

Abstract

Drug resistant superbug infection is one of the foremost threats to human health. Plasmonic nanoparticles can be used for ultrasensitive bio-imaging and photothermal killing by amplification of electromagnetic fields at nanoscale “hot spots”. One of the main challenges to plasmonic imaging and photothermal killing is design of a plasmonic substrate with a large number of “hot spots”. Driven by this need, this article reports design of a three-dimensional (3D) plasmonic “hot spot”-based substrate using gold nanoparticle attached hybrid graphene oxide (GO), free from the traditional 2D limitations. Experimental results show that the 3D substrate has capability for highly sensitive label-free sensing and generates high photothermal heat. Reported data using p-aminothiophenol conjugated 3D substrate show that the surface enhanced Raman spectroscopy (SERS) enhancement factor for the 3D “hot spot”-based substrate is more than two orders of magnitude greater than that for the two-dimensional (2D) substrate and five orders of magnitude greater than that for the zero-dimensional (0D) p-aminothiophenol conjugated gold nanoparticle. 3D-Finite-Difference Time-Domain (3D-FDTD) simulation calculations indicate that the SERS enhancement factor can be greater than 104 because of the bent assembly structure in the 3D substrate. Results demonstrate that the 3D-substrate-based SERS can be used for fingerprint identification of several multi-drug resistant superbugs with detection limits of 5 colony forming units/mL. Experimental data show that 785 nm near infrared (NIR) light generates around two times more photothermal heat for the 3D substrate with respect to the 2D substrate, and allows rapid and effective killing of 100% of the multi-drug resistant superbugs within 5 minutes.

Nanoarchitecture Based SERS for Biomolecular Fingerprinting and Label-Free Disease Markers Diagnosis

“…Copyright 2014 American Chemical Society). (E) Raman intensity from p -aminothiophenol on nanoparticle attached 3D GO based SERS substrate (Reproduced with permission from ref (30). Copyright 2016 Royal Society of Chemistry).…”

“…15−25 Although the first paper on SERS was published in 1974, 8 which is more than 40 years ago, its applications are still rare outside the spectroscopy community and it is mainly due to the fact that until now scientists are facing enormous challenges on how to design reproducible plasmonic SERS substrate with large number of “hot spots” and also how to manipulate light on the “hot spots”. 20−30 …”

Development of a SERS Probe for Selective Detection of Healthy Prostate and Malignant Prostate Cancer Cells Using ZnII

“…In the next step, we have performed the synthesis of gold nanoparticle using gold chloride, sodium borohydride and sodium citrate using our reported method 24,28,31–32 . After that, we have attached p-(imidazole)azo) benzenethiol via thiol group as shown in Figure 1C.…”

“…Gold nanoparticles of 25 nm in size were synthesized by using HAuCl 4 , 3H 2 O, sodium boro-hydride (NaBH 4 ) and ascorbic acid as we have reported before 24,28,31–32 . In brief, 0.01 wt.% solution chlorauric acid was heated to boiling and then trisodium citrate dihydrate solution was quickly added.…”

“…Since in Raman spectroscopy, scattering efficiency is extremely weak, surface-enhanced Raman spectroscopy (SERS) based on nanotechnology is becoming an excellent bio-analytical tool 21–30 . In case of SERS, the Raman signals intensity can be enhanced by 10 8 –10 14 orders of magnitude via electromagnetic fields generated by the “hot spots”, as a result, SERS can be used for ultrasensitive sensing applications 24–32 . In addition, SERS provides several advantages over fluorescence-based assays 21–30 and these are as follows: 1) near IR light can be easily used to avoid tissue autofluorescence and to enhance significantly the tissue penetration depth; (2) very narrow spectral widths in Raman bands allow multiple labels detection under single NIR light source and (3) due to the non-resonance condition, photo-bleaching issues are minimum for SERS.…”