Indian research team builds eco-friendly Cholesterol detection sensor

A research team at the Institute of Advanced Study in Science and Technology (IASST), Guwahati, has developed a novel optical and electrical sensing platform for detecting cholesterol. The platform aims to diagnose several chronic and lifestyle-related diseases early.

The innovation integrates phosphorene quantum dots with silk fibre to create a sensitive and eco-friendly point-of-care (POC) system capable of trace-level detection in real-world biological samples. Currently at laboratory scale, the POC sensing platform, designed for routine monitoring, addresses the increasing need for precise, rapid, and cost-effective methods to detect key biomarkers such as cholesterol.

Cardiovascular diseases like hypertension, myocardial infarction, and stroke are commonly linked to abnormal cholesterol levels. The newly proposed sensor can support personalised health monitoring and early intervention by identifying biochemical changes before clinical symptoms emerge.

Synthesised Sensor Traces Cholesterol Levels

Cholesterol, a lipid produced by the liver, is essential for the human body, contributing to the formation of vitamin D, bile acids, and steroid hormones. It exists primarily in two forms: low-density lipoprotein (LDL), known as ‘bad’ cholesterol due to its tendency to accumulate in arteries, and high-density lipoprotein (HDL), referred to as ‘good’ cholesterol. Imbalances in these levels can lead to plaque formation, restricting blood flow, and triggering various health disorders.

The IASST research group, supervised by retired professor Neelotpal Sen Sarma, integrated functionalised silk fibre into a cellulose nitrate membrane to construct an electrical sensing system capable of detecting cholesterol at trace levels, even below the typical reference range. Nasrin Sultana, a DST INSPIRE Senior Research Fellow, conceptualised the study and conducted the methodology design, data curation, and formal analysis. Dr Asis Bala, Associate Professor (Pharmacology & Drug Discovery) at IASST oversaw the animal studies and the test using rat blood serum.

Speaking exclusively with Voice&Data, Sultana explained that among different two-dimensional materials, the research focused on phosphorene, which was modified with silk fibre extracted from silk cocoons. “The resulting phosphorene-silk fibre nanomaterial exhibits enhanced optical properties, allowing us to develop an optical sensing platform specifically for cholesterol detection.”

The optical sensing platform operates on the inner filter effect (IFE) principle, specifically the primary IFE mechanism, where cholesterol molecules absorb the excitation energy of phosphorene quantum dots, altering fluorescence emission. This design ensures high selectivity without covalent bonding, enhancing its reliability in real-time bio-detection scenarios.

Elaborating on the sensing process, Sultana said, “When we add cholesterol to our material solution, the fluorescence intensity increases, and by measuring this change with a photospectrometer, we can determine how much cholesterol is present—even in trace amounts.”

The composite—phosphorene quantum dots functionalised with silk fibre (Ph–SF) were synthesised using a single-step hydrothermal process. The resulting material showed dual peaks in UV-Vis spectra, confirming the stability and presence of both components. Transmission electron microscopy confirmed the successful synthesis of Ph–SF quantum dots, averaging ~8 nm in size.

It demonstrated detection limits of 22 nanomolar (nM) for aqueous media, 21.7 nM for human blood serum, 11.01 nM for rat blood serum, and 19.9 nM for milk, within a linear range of 0–80 microlitres for concentration values between 4.5–36.36 micromolar (μM).

Dual-Mode Sensing and Real-World Application

The sensing device uses a dual-mode system—optical and electrical—to detect cholesterol with high selectivity and minimal environmental impact. Notably, the electrical sensing element of the device produces no electronic waste, offering an added sustainability advantage.

The electrical sensor was fabricated using a biodegradable cellulose nitrate membrane (CNM) with copper tape electrodes spaced 0.4 mm apart. When coated with Ph–SF and exposed to cholesterol, the device’s current increased from 7.74 × 10⁻⁶ A to 2.16 × 10⁻⁵ A.

Detection limits via the electrical method were measured at 0.263 μM in aqueous media, 1.69 μM in human blood serum, 1.402 μM in rat blood serum, and 1.192 μM in milk, over a linear range of 1–5 millimolar (mM). After cholesterol exposure, transport number analysis confirmed partial ionic conductivity, suggesting ionic interaction mechanisms.

“We tested our platform in real samples like human blood serum, rat serum, and milk to ensure practical applicability,” Sultana added. “The device operates externally by analysing extracted blood samples, not internally.” The detection method showed consistent results across these different media, indicating its potential adaptability for real-world applications.

The innovation has been documented in the peer-reviewed journal Nanoscale, published by the Royal Society of Chemistry. According to the researchers, this approach could pave the way for portable, user-friendly diagnostic tools for continuous health monitoring, especially in resource-constrained environments.

The platform is expected to contribute significantly to the development of decentralised health monitoring systems, making it easier for individuals to track key biomarkers without the essential centralised laboratory infrastructure.