Better roadside drug detection
New Australian standards mandate that the cannabis test must have a THC cut-off at 15 ng/mL. But with better sensitivity this will reduce the number of false readings.
IDEAL Hub postdoc fellow Dr Giles Kirby (UniSA) has been working closely with the industry partner, Alcolizer, to develop the next generation of rapid, low-cost, and sensitive drug detection devices. The project seeks to solve challenging sample collection problems involving the detection of drugs in biofluids such as saliva. With our new method we have achieved below 10 ng/mL with scope to improve this further. We have also seen excellent increases in sensitivity from other drugs such as methamphetamine, which we can quantify accurately down to 1.75 ng/mL.
Dr Kirby measuring surface antigens on T-cells using a flow cytometer.
What makes our approach different is the combination of methods providing both fast and quantitative results. We see this technology as the platform to supersede lateral flow assays, a technology that has been around for over 60 years and is reaching the limits of what it is capable of.
“Fast detection of small molecules remains a critical challenge. The platform technology that we’ve developed has potential in environmental monitoring, healthcare and bioprocessing.” – Dr Kirby, UniSA
The team has addressed key scientific hurdles and proven the technology. The next phase is focused on translation – understanding how to transform this technology into an off-the-shelf product. The research gives our industry partner a competitive edge placing them in an excellent position to become market leaders in this growing sector.
Next generation of rapid point-of-care diagnostic systems
There is growing demand for portable “lab-on-a-chip” (LOC) diagnostic devices that allow us to bring sample analysis and testing out into the real world. Current conventional analytical technologies require specialized equipment and skilled staff, and often testing is undertaken in large diagnostic laboratories with slow turnaround times.
It is widely believed that the key to achieving high-performance in a compact LOC device is the integration of highly sensitive optical components. The integration of optics into such devices is expected to allow the sensitivity, selectivity and speed of detection requirements to be met for various biosensing and point-of-care applications.
IDEAL Hub Postdoc Fellow Dr Nicolas Riesen (UniSA) has been collaborating with industry partner, ULVAC Inc. and the IDEAL Hub team to develop the next generation of optofluidic biosensors. These state-of-the-art integrated optical components aim to enhance the detection limits of LOC devices down to extremely low levels (e.g. femtomolar concentrations). However, the miniaturisation of various laboratory functions into a LOC platform is difficult without losing sensitivity and performance, especially given the smaller sample volumes used.
Schematic of a pillar cuvette with immobilised WGM whispering gallery mode microspheres for multiplexed sensing and SEM image of one of the immobilised microspheres.
These biosensors are based on the pillar cuvette platform. A pillar cuvette is an array of pillars dry-etched into glass which allows for a thin film of liquid to spread out and wick across the open area. The thin film of liquid rapidly evaporates allowing for more liquid to be drawn in from an adjoining reservoir.
This platform is simple and cost-effective. To enhance the performance of this platform various optical elements are being embedded called ring resonators and whispering gallery mode (WGM) resonators (Riesen et al., Sensors 2022, 22, 4135). In the case of whispering gallery mode resonators, the IDEAL Hub team is using microspheres which are doped with a phosphor material. When the phosphor is excited, light circulates inside the microspheres – a phenomenon known as whispering gallery modes. Since the whispering gallery modes are confined and orbit thousands of times inside the microsphere, they can interact thousands of times with molecules on the surface of the microsphere. This results in a sensor with extreme sensitivity. This platform is used to create simple and practical biosensors with extreme sensitivity suitable for detecting analytes of very low concentration as required for various point-of-care diagnostic applications.
The realisation of enhanced detection limit and practical optical LOC technologies is expected to have significant downstream benefits including in terms of point-of-care diagnostics. Cancer markers exist at very low levels at early stages of cancer and during relapse, and therefore require ultra-low detection limits to ensure detection. Early detection of diseases with cost-effective take-home kits could be a game-changer in combating disease and illness within the community.
Sensing inflammatory bowel events
Imagine the life of someone with an inflammatory bowel disease. They live with the constant risk of having their lives interrupted at unexpected moments by pressing needs to find a bathroom. This is accompanied by extensive pain, discomfort and sometimes embarrassment as they endure their gastrointestinal cramps and spasms. The lives of people with inflammatory bowel diseases can be vastly improved if there was a way to predict and diagnose their condition simply by doing a quick test of their stool.
Associate Professor Charles Cranfield (UTS), IDEAL Hub Chief Investigator, along with PhD candidate Shashikala Randunu (UTS) have developed a sensor capable of measuring the activity of a particular enzyme called PLA2 in small amounts of stool samples. The presence of this enzyme in stool samples is a good indicator that a person is suffering from an inflammation in their bowels. For people who endure inflammatory bowel conditions, this sensor will enable them to more accurately predict when a flare event is likely to occur and better manage their condition. For clinicians, this sensor will give them the confidence they need to recommend treatments for inflammatory bowel diseases.
Prototype point-of-care sensor
It is the all-Australian technology platform from our commercial partner, SDx Surgical Diagnostics Pty Ltd, that enables us to measure the activity of PLA2 enzymes. Using special chemistries anchored to gold electrodes, we are able to test the activity of this enzyme and not just the presence of the enzyme, by using simple electrical spectroscopy techniques. As the enzyme reacts with the chemistries on the electrodes, electrical signals are altered, indicating that PLA2 is active in stool samples. This tells us that there is likely to be some portion of the gut that is inflamed.
Through the support of the IDEAL Hub we have conducted blind trials using actual human stool samples which have verified the utility of this technology. This has inspired further research and development, leading to the production of a prototype point-of-care sensor designed in collaboration with the Australian National Fabrication Facility.