# Development of a handheld PEST-pen device for the rapid detection of organophosphate insecticides on food and clothing

> **NIH NIH R44** · PLANTVAX, INC. · 2020 · $705,843

## Abstract

ABSTRACT
The neurotoxicity of organophosphate (OP) insecticides in humans may result from dermal or
inhalation exposure on clothing and machinery or orally from the residue on food. In the latter
context, the health consequences associated with the use of OP insecticides, especially in
children, could be reduced by monitoring produce and eliminating the consumption of OP-
contaminated food. PlantVax currently employs the Nicotiana benthamiana (N.b.) plant
expression system to produce high levels of recombinant human acetylcholinesterase (rHuAChE)
which is used in devices e.g. the FLIR CAD-pen, for the detection of trace amounts of OP nerve
agents for military purposes. In this proposal, PlantVax aims to develop for food safety purposes,
a simplified, hand-held, portable, self-contained and inexpensive PEST-pen to rapidly detect
phosphorothionate insecticides on food, clothing and machinery. However unlike active OP nerve
agents, OP insecticides exhibit a wide range of bimolecular rate constants (ki) ranging from ki =
101M-1min-1 to 109M-1min-1) against esterases e.g AChE. These fall into two categories (i) those
with high ki (>104M-1min-1) which contain an “oxon-like” bond and can be used immediately to
produce a functional PEST-pen in Phase II and (ii) those with low ki (~101-3M-1min-1) which have a
P=S bond and will need to be converted by oxidative desulfuration into the active oxon form by
cytochrome P450 and NADPH for their toxicity and detection. The new PEST-pen device will
utilize the same esterase-based embedded chemistry as the CAD-pen with a yellow to red color
change as a read-out, but with two important modifications required to increase the ki and thus
the color change (i) the use of recombinant human CES (rHuCES) also produced in N.b. plants
immobilized into the pen sponge as the target enzyme since Phase I results indicated a 10-fold to
1,000-fold increase in ki against both thion and oxon forms with this enzyme and (ii) the
integration of P450 and NADPH into the pen to convert kilow to kihigh to enable the detection of
many highly toxic OP insecticides which might have otherwise gone undetected. In Phase II, the
chemistry will be optimized in twenty functional printed pens and then two thousand beta-
prototype PEST-pens, which are compatible with the chemistry, will be designed and produced by
injection molding for testing in the field. It is planned to initially test vegetable and fruit samples in
markets and farms in the USA, Asia and Central America to demonstrate the utility of the PEST-
pen globally.

## Key facts

- **NIH application ID:** 10079784
- **Project number:** 2R44ES029405-02A1
- **Recipient organization:** PLANTVAX, INC.
- **Principal Investigator:** Yvonne J Rosenberg
- **Activity code:** R44 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $705,843
- **Award type:** 2
- **Project period:** 2018-03-01 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10079784

## Citation

> US National Institutes of Health, RePORTER application 10079784, Development of a handheld PEST-pen device for the rapid detection of organophosphate insecticides on food and clothing (2R44ES029405-02A1). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10079784. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*