This month we shine a light on a publication by Chen-Ji Huang and colleagues from the Institute of Biomedical Engineering and Nanomedicine at the National Health Research Institutes at Taiwan. Their study deals with microplastics, which is a major environmental challenge.
In this publication they demonstrate an innovative method they have developed that uses surface plasmon resonance (SPR) biosensors to detect even small amounts of microplastics in water. Various methods were used in this publication to study microplastics-detection, including protein purification using Ni-NTA magnetic beads.
Microplastics in our environment and their potential health risks
Microplastics are small pieces of plastic that can be found widespread all over the world. They have been detected in the Arctic, oceans, seas, rivers, lakes, rain, snow, soil, and even in the environment. This global presence means that a wide range of ecosystems and living organisms are directly or indirectly affected by microplastic contamination.
In general, microplastics have been found in over 1,300 aquatic and terrestrial species. These range from invertebrates at the base of the food web to apex predators and the effects were observed at all levels of biological organization reaching from a cellular level to the entire ecosystem. Aquatic organisms are particularly affected due to the plastic waste in aquatic systems, but the impact extends far beyond marine life.
Humans are also increasingly exposed to microplastics, e.g. through food consumption, such as eating fish and mussels that have ingested these particles. On average, a person consumes between 39,000 and 52,000 microplastic particles per year through food. Additionally, microplastics can be ingested via plastic bottled water and food delivered in plastic takeaway containers.
Fig. 1: Water polluted with microplastics can contaminate the aquatic organisms living in it, as well as our drinking water, with microplastics. Drinking water in plastic bottles is even more impacted. Soil can also be contaminated with microplastics, which can then be taken up by plants growing on it or even farm animals. The human body can then absorb microplastics through food or drink. Not only plastic water bottles, but also takeaway food containers can be a possible source of microplastics. The human body can also absorb microplastics through the skin, for example by using skin care products.
Beyond ingestion, microplastics can enter the human body through other routes. They can be absorbed through the skin via personal care products like facial creams or even inhaled from the air. Agricultural systems are also at risk, as contaminated water can introduce microplastics into the soil and food chain, further increasing human exposure.
This widespread exposure could lead as a consequence to significant health risks. Scientific research has shown that microplastics can damage living cells and induce a range of toxic effects, including oxidative stress, metabolic disorders, immune system disruptions, neurotoxicity, and reproductive or developmental harm.
From an environmental perspective, the situation is equally alarming. With evidence of microplastic contamination across species and ecosystems, projections suggest that environmental contamination could double by 2040. This could lead to large-scale ecological damage if no significant action is taken.
Current challenges in microplastics detection
Currently, scientists usually identify microplastics applying special chemical tests, like Raman Spectroscopy, which analyses how light changes when it interacts with a material to reveal its molecular vibrations, and FTIR (Fourier-Transform Infrared Spectroscopy), that measures the infrared light absorption of each sample for the identification of the chemical structure.
However, these methods have their limits, as the detection of microplastics is an issue, when the microplastics are in liquids or water. This complicates the process of accurate detection by the instruments, necessitating preliminary separation. Furthermore, the size of the particle is also a limit of the detection methods. Research has indicated that microplastics can accumulate within the human body over time. For instance, larger microplastics (approximately 20 µm) tend to accumulate in specific organs, such as the liver, while smaller ones (5 µm) exhibit different distribution patterns. It is imperative to identify more efficient and rapid methods of detecting these minute particles, particularly at low concentrations, to comprehensively assess their impact on human health.
Addressing this problem, the researchers combined biosensors and Surface Plasmon Resonance (SPR) to develop a new method for detecting microplastics. Biosensors, like ELISA, can identify small particles such as viruses, while SPR uses light to observe real-time molecular interactions by measuring changes in light reflection when molecules bind to a metal surface. Most SPR research focuses on smaller molecules, leaving a gap in knowledge about larger microplastics (over 10 μm). This study demonstrates the use of SPR to detect low concentrations of microplastics in real time by analyzing their interactions with estrogen receptors (ERs), creating a more efficient detection system.
SPR Biosensors as a novel approach to detect low-concentrated microplastics
In their study, Huang et al. successfully developed a method to detect and measure microplastics (about 20 µm in size) using a biosensor based on Surface Plasmon Resonance (SPR). Therefore, the researchers prepared 20 µm microplastic pieces to study their movement and properties using Liquid Chromatography and SPR.
Method Spotlight: Surface Plasmon Resonance
Surface Plasmon Resonance (SPR) is a technique used to study how molecules interact with each other in real time, without the need for labels or dyes. It works by shining a light on a thin metal surface, usually gold, and detecting changes in the reflection of the light as molecules bind to the surface. These changes indicate the strength of the bond and help researchers analyse molecular interactions and understand molecular mechanisms.
They used specifically Polyethylene (PE), Poly Carbonate (PC) and Polyvinyl Chloride (PVC) as different types of microplastics. Thereby, they found that the surface charge of the plastics influences the movement and the interaction with ERs on cells. They observed that microplastics move in rolling patterns on these receptors. The amount of microplastics could be measured with SPR, revealing different types of plastics: PS, PVC and PE. These bind to ERs with different strengths - a useful finding for identifying different types of microplastics. Subsequently, the interaction between microplastics and ERs were verified by performing ELISA using the Ni-NTA magnetic beads of Cube Biotech to verify the interaction between the microplastics and ERs.
In general, the findings suggest that SPR can be a useful tool for studying microplastics' impact on health, and in the future, it could help with detecting microplastics in the environment and understanding their effects on humans.
Future prospects and potential
The new method effectively detects low concentrations of microplastics by enhancing their surface charge through ERs, allowing particles like PS to persist in the system longer. This approach not only quantifies but also identifies microplastics in real-time, detecting particles as small as 20 μm, unlike conventional techniques.
This real-time detection method is valuable for environmental and health research, as it identifies microplastics by shape, size, and surface properties. It offers insights into how these factors influence toxicity, with studies showing that particle size and surface charge significantly affect the biological impact of microplastics. The integration of SPR and biosensor technology makes this method an innovative tool for assessing health effects from microplastic exposure.
Beyond its scientific value, the method also brings practical advantages. Measuring microplastics directly in water eliminates the time-consuming step of separating particles from liquid samples. This efficiency not only accelerates research but also supports environmental monitoring efforts. Detecting microplastics in sources like bottled water or aquatic environments helps prevent their entry into the human food chain.
Ultimately, this technology contributes to both environmental protection and public health. As it becomes more widely applied, it could help develop targeted strategies to reduce microplastic pollution and its risks, thereby, preserving ecosystems and safeguarding human health through improved food and water quality.
.webp "Schematic illustration of Surface Plasmon Resonance")