Summary

Polymer gloves are used as personal protective equipment (PPE) in many professional fields where chemical risks exist. Their effectiveness in blocking the passage of certain contaminants must be measured by accurate, standardized test methods. Measurements of chemical resistance are generally done by using a permeation cell, a small device containing two reservoirs separated by a membrane, the barrier potential of which one wishes to measure: one reservoir contains the contaminant while the other contains a medium that collects the contaminant after it has passed through the membrane. Throughout the experiment, the collector medium is sampled to measure its contaminant content. The length of time the membrane resists the passage of contaminants and their speed in passing through it are measured in that way.

In North America, tests for contaminant permeation through polymer gloves are guided by standards (e.g., ASTM-F739). This method is well supported for measuring the passage of solvent molecules through gloves. However, if one wants to measure the passage of less volatile molecules or low-concentration substances that are potentially highly toxic (e.g., pesticides or chemotherapy drugs), or of nanoparticles (NPs), the detection limits of current analytical techniques are generally inadequate. They do not allow one to measure the kinetics of contaminant passage through the gloves in real time; thus, it is impossible to derive certain crucial data from the permeation curves, such as the diffusion coefficient, passage time (or latency period before permeation), permeation rate, and influx of contaminants in the membrane.

To accurately and quantitatively measure the kinetic parameters describing the passage of contaminants through gloves, it is necessary to develop a permeation cell that uses a detection method with a very high sensitivity level and that allows continuous measurement. In this research project, a new technology was developed in the form of a permeation cell adapted to nuclear imaging by means of positron emission tomography (PET). PET makes it possible to detect molecules and NPs with a much higher sensitivity level than the spectroscopic or spectrometric methods usually used to detect the permeation process. The device was created using a polymer whose nature and dimensions do not attenuate the radiation emitted by the radioisotopes used to mark the molecules and nanoparticles.

The new PET-based permeation cell technology was tested on samples of the latex and nitrile gloves most commonly used in biomedical laboratories and nuclear medicine clinics in hospitals. Gold nanoparticles (AuNPs) were used as a type contaminant, since this kind of product, which is used increasingly frequently in medicine, is particularly difficult to detect with the usual measurement techniques applied in permeation tests. The data acquired in these tests revealed NP permeation profiles at a very high temporal resolution with a detection sensitivity that made it possible to calculate all the main parameters describing the permeation of contaminants through membranes (diffusion coefficient, latency period, permeation rate, etc.).

The latency periods at the start of permeation, measured in the upstream compartment, were all greater than 3 hours, which is substantially longer than the usual maximum duration for wearing the same pair of polymer gloves. These results confirm that a minuscule fraction of NPs passes through nitrile and latex membranes during the period when polymer gloves are used as PPE (less than 2 hours) and thus that these gloves offer excellent skin protection against the ultrasmall NPs used in the biomedical field, and particularly AuNPs. This technology will also be useful in the case of contaminants that are generally very difficult to detect with known measurement techniques (e.g., pesticides, chemotherapy drugs, viruses).