Localized surface plasmon resonance (LSPR) is a nanoscale phenomenon associated with noble metal nanostructures that has long been studied and has gained considerable interest in recent years. These resonances produce sharp spectral absorption and scattering peaks, along with strong electromagnetic near-field enhancements. Over the past decade, advancements in the fabrication of noble metal nanostructures have propelled significant developments in various scientific and technological aspects of LSPR. One notable application is the detection of molecular interactions near the nanoparticle surface, observable through shifts in the LSPR spectral peak. This document provides an overview of this sensing strategy. Given the broad and expanding scope of this topic, it is impossible to cover every aspect comprehensively in this review. However, we aim to outline major research efforts within the field and review a diverse array of relevant literature. We will provide a detailed summary of the physical principles underlying LSPR sensing and address some existing inconsistencies in the nomenclature used. Our discussion will primarily focus on LSPR sensors that employ metal nanoparticles, rather than on those utilizing extended, fabricated structures. We will concentrate on sensors where LSPR acts as the primary mode of signal transduction, excluding hybrid strategies like those combining LSPR with fluorescence. Additionally, our examination of biological LSPR sensors will largely pertain to label-free detection methods, rather than those that use metal nanoparticles as labels or as means to enhance the efficacy of a label. In the subsequent section of this review, we delve into the analytical theory underpinning LSPR, exploring its physical origins and its dependency on the material properties of noble metals and the surrounding refractive index. We will discuss the behavior of both spherical and spheroidal particles and elaborate on how the LSPR response varies with particle aspect ratio. Further, we detail the fundamentals of nanoparticle-based LSPR sensing. This includes an exploration of single-particle and ensemble measurements and a comparative analysis of scattering, absorption, and extinction phenomena. The discussion will extend to how these principles are applied in practical sensing scenarios, highlighting the key experimental approaches and measurement techniques.

The introduction of point-of-care testing (POCT) has revolutionized medical testing by allowing for simple tests to be conducted near the patient’s care point, rather than being confined to a medical laboratory. This has been especially beneficial for developing countries with limited infrastructure, where testing often involves sending specimens off-site and waiting for hours or days for results. However, the development of POCT devices has been challenging, with simplicity, accuracy, and cost-effectiveness being key factors in making these tests feasible. Nanotechnology has played a crucial role in achieving this goal, by not only making the tests possible but also masking their complexity. In this article, recent developments in POCT devices that benefit from nanotechnology are discussed. Microfluidics and lab-on-a-chip technologies are highlighted as major drivers of point-of-care testing, particularly in infectious disease diagnosis. These technologies enable various bioassays to be used at the point of care. The article also addresses the challenges faced by these technological advances and interesting future trends. The benefits of point-of-care testing are significant, especially in developing countries where medical care is shifting towards prevention, early detection, and managing chronic conditions. Infectious disease tests at the point of care in low-income countries can lead to prompt treatment, preventing infections from spreading.

Optical biosensing has emerged as a vital tool for real-time, sensitive detection of biological analytes, with aptamers and antibodies leading as key molecular recognition elements. This review examines and compares their distinct roles, advantages, and limitations in optical biosensing. Antibodies, celebrated for their high specificity and mature production protocols, are often preferred in clinical diagnostics. However, challenges like cross-reactivity, environmental sensitivity, and production costs prompt exploration of alternative biorecognition molecules. Aptamers, nucleic acid–based recognition elements, offer several unique advantages, such as ease of synthesis, chemical stability, and amenability to modifications for improved target binding. While their relatively recent discovery means fewer standardized protocols and clinical applications compared to antibodies, aptamers show promise in complex sample matrices and emerging sensor platforms. This review also explores technological advances in both aptamer and antibody integration, surface modification strategies to enhance binding specificity and orientation, and regeneration methods to ensure biosensor reusability. Through a comprehensive comparison, the article aims to identify scenarios where one molecular recognition element holds distinct advantages over the other, paving the way for strategic applications in diagnostics, food safety, and environmental monitoring. In this review, we have explored the advancements and challenges associated with optical biosensing technologies, with a particular focus on LSPR-based sensors. Recent developments in nanoparticle fabrication, hybrid sensor platforms, and external stimulus-responsive systems have opened new avenues for biosensing applications in clinical diagnostics, environmental monitoring, and food safety. The review also discussed the integration of optical biosensors with Raman spectroscopy for enhanced analytical capabilities and highlighted innovations in metamaterial-based sensors for improved sensitivity and specificity. Despite these advances, several challenges remain, including surface stability, reproducibility, and limitations in detecting low-abundance analytes. Addressing these challenges will require further improvements in device design, bioreceptor immobilization strategies, and signal enhancement techniques. Future research efforts should also focus on the development of portable and cost-effective biosensing platforms that can be applied in resource-limited settings. Ultimately, this review provides valuable insights into future trends in aptamer and antibody-based biosensors, encouraging cross-disciplinary collaboration and innovation.

The potential threat posed by disease outbreaks to diagnostic instruments demands the development of more effective biosensor technologies to counteract the risks. Diseases like SARS-CoV-2, Ebola, malaria, cholera, and many more have demonstrated beyond the limits of health care that new advancements are required for early detection and diagnosis. The rising number of diseases outbreaks has led to an increasing demand for biosensors that are more effective and quicker to utilize in healthcare settings. A biosensor incorporated with microfluidic chips offers an improved detection compared to traditional or classical biosensors. Microfluidic chips improve the performance of the biosensors by allowing automation, mixing, separation, throughput processing, and transport of the analytes to desired reactors. A biosensor incorporated with a microfluidic chip has improved sensitivity, easy operation and can use small volumes of samples to process the results. The effectiveness of biosensors depends also on the materials used in its fabrication and there are many materials used for fabrication which are reviewed in this work. This paper reviews the potential advantages of the use of microfluidic chips to enhance the performance of biosensors, materials used to fabricate the chips, and potential electrodes incorporated into microfluidic chips which improve the detection time by shortening the processing time for biosensors at the point of care service. This work also reviews new technologies which are not previously addressed other reviews including, integration of cell-imprinted polymers with microfluidic sensors and delved into future technologies outlook.

Microfluidic devices have become a vastly popular technology, particularly because of the advantages they offer over their traditional counterparts. They have such a wide range of uses and can make complex tasks quite efficient. One area of research or work that has benefited greatly from the use of microfluidics is biosensing, where microfluidic chips are integrated into biosensor setups. There are growing numbers of applications of microfluidics in this area as researchers look for efficient ways to tackle disease diagnostics and drug discovery, which are critical in this era of recurring pandemics. In this work, the authors review the integration of microfluidic chips with biosensors, as well as microfluidic applications in biosensing, food security, molecular biology, cell diagnostics, and disease diagnostics, and look at some of the most recent research work in these areas. The work covers a wide range of applications including cellular diagnostics, life science research, agro-food processing, immunological diagnostics, molecular diagnostics, and veterinarian diagnostics. Microfluidics is a field which combines fundamental laws of physics and chemistry to solve miniaturization problems involving fluids at the nanoscale and microscale, and as such, the authors also examine some fundamental mathematical concepts in microfluidics and their applications to biosensing. Microfluidics has relatively new technologies with great potential in terms of applications.

Rapid increases in diseases and pandemics over the past years have led to the development of more affordable and accessible biosensing equipment, especially in underdeveloped regions. One of the open-source hardware that has the potential to develop advanced health equipment is the Arduino platform. This review emphasizes the importance of open-source technology, specifically the Atmel family of microcontrollers used in the Arduino development board, and the applications of the Arduino platform in biosensing technologies to advance PoC devices. Furthermore, the review highlights the use of machine learning algorithms to enhance the functionality of user-defined prototypes, aiming to realize PoC devices. It also addresses the successes and limitations of microcontrollers and machine learning in the development of PoC devices using open-source technology. The primary purpose of this paper is to investigate how the Arduino platform can be leveraged to create effective and affordable biosensing solutions, by examining the integration of Arduino with various types of biosensors. The review showcases the potential of Arduino to democratize and innovate biosensor technology. Lastly, this paper extends the investigation of applications of Arduino to general health care and environmental monitoring.