Inexpensive Near-Infrared Fluorimeters: Enabling Translation of nIR-Based Assays to the Field

Abstract

The practical impact of analytical probes that transduce in the near-infrared (nIR) has been dampened by the lack of cost-effective and portable nIR fluorimeters. Herein, we demonstrate straightforward designs for an inexpensive microplate reader and a portable fluorimeter. These instruments require minimally complex machining and fabrication and operate with an open-source programming language (Python). Complete wiring diagrams, assembly diagrams, and scripts are provided. To demonstrate the utility of these two instruments, we performed high-throughput and field-side measurements of soil samples to evaluate the effect of soil management strategies on extracellular proteolytic, cellulolytic, and lignin-modifying activities. This was accomplished with fluorescent enzyme probes that utilized uniquely sensitive transducers exclusive to the nIR spectrum, single-walled carbon nanotubes. We also used the portable fluorimeter to evaluate spatial variations of proteolytic activity within individual field plots, while minimizing the effects of soil storage and handling. These demonstrations indicate the utility of these fluorimeters for translating analytical probes that operate in the nIR beyond the laboratory and into actual use.

Biosensing with Fluorescent Carbon Nanotubes

“…Apart from exploiting the decreasing sensitivity of Sidetectors in the NIR, efforts have been made to promote NIR-fluorescent transducers using straightforward designs for inexpensive NIR fluorimeters. [167] Instead of using high-cost InGaAs photodiode arrays,s ingle InGaAs diodes were combined with am otorized stage controlled with an open source programming language.T he robustness of these devices outside of the laboratory was demonstrated in ah igh-throughput format with field-side measurements of soil samples.F uture developments might also show remote detection using pure (6,4)-SWCNTs with Si-based cameras and also versatile use as smart surfaces,f or example,f or monitoring contamination with pathogens,s uch as bacteria, on medical surfaces or even implants.…”

Detection of Cell Membrane Interactions with Lipid-functionalized Single-walled Carbon Nanotubes

“…Additionally, this solution-phase sensor can be easily adapted to titer-plate assays, making it suitable for high-throughput screening operations. The facile means of sensor preparation, compatibility with a ubiquitous form factor, and the accessibility of open source near infrared uorimetry tools 22 makes this method easily adaptable for use by other laboratories.…”

“…Further tests were performed on a custom near-infrared plate reader (described in a previous work) 22 . Initial disruption tests were performed with PC-SWNT diluted to a concentration of 2.5 mg/mL PC.…”

“…The combined surface sensitivity and modular method of functionalization result in a powerful sensing platform where transduction may occur without the conventional energy donor-acceptor pair (e.g., tethered FRET pair or quenching agent). While much established work has been applied to sensing binding events [18][19][20] , recent studies have demonstrated SWNT's ability to transduce direct modi cation to the corona phase 21,22 . This manuscript represents a shift from sensing chemical modi cations to the corona phase (e.g., hydrolytic enzyme modi cation) to detecting structural changes (e.g., pore formation and disruption).…”

Biosensing with Fluorescent Carbon Nanotubes

“…Different polymer wrappings consisting of polysaccharides and polypeptides were used to study cellulase, pectinase, and bacterial protease. Most recently, they used this approach to evaluate the enzyme activity in soil using a low‐cost multiplexed and portable fluorimeter able to perform the measurement outside the laboratory only minutes after extraction from the field [167] . As a consequence of the fresh nature of the soil sample, field tests indicated activities an order of magnitude larger than those obtained in benchtop experiments.…”