DNA-functionalized photonic crystal microspheres for multiplex detection of toxic metal ions

Heavy metal ion sensing strategies using fluorophores for environmental remediation

The main aim of this review is to provide an extensive summary of the latest advances within the emerging research area focused on detecting heavy metal ion pollution, particularly sensing strategies. The review explores various heavy metal ion detection approaches, encompassing spectrometry, electrochemical methods, and optical techniques. Numerous initiatives have been undertaken in recent times in response to the increasing demand for fast, sensitive, and selective sensors. Notably, fluorescent sensors have acquired prominence owing to the numerous advantages such as outstanding specificity, reversibility, and sensitivity. Further, it also explores the discussion of various nanomaterials employed in sensing heavy metal ions. In this regard, the exclusive emphasis is placed on fluorescent nanomaterials based on organic dyes, quantum dots, and fluorescent aptasensors for metal ion removal from aqueous systems to identify the destiny of dangerous heavy metal ions in clean circumstances.

Construction of hybridization chain reaction induced optical signal directed change of photonic crystals-DNA hydrogel sensor and its visual determination for aflatoxin B1

Herein, we have introduced hybridization chain reaction (HCR) into the photonic crystals (PhCs) hydrogel, for the first time, realizing HCR for inducing the change of the optical signal of PhCs hydrogel and using this hydrogel as a sensor for determination of the aflatoxin B1 (AFB1). By using specific sequences as the cross-linker, the extension of the cross-linker by HCR drives the swelling of the hydrogel, and the optical property of 2D PhCs array converts this swelling into a change of the Debye diffraction ring. Moreover, by further selecting the aptamer to construct the cross-linker, the hydrogel is also endowed with a unique capability for AFB1, making the hydrogel a novel sensor based on the signal amplification strategy. The results show that the designed hairpin DNAs can effectively trigger the HCR and cause the swelling of hydrogel, and the hydrogel sensor has a good determination performance and high specific recognition for AFB1.

Hydrogel Encapsulated Core-Shell Photonic Barcodes for Multiplex Biomarker Quantification

Acute myocardial infarction (AMI) is one of the most fatal diseases in the world in recent decades. Because rapid and accurate determination of AMI has the potential to save millions of lives globally, the development of new diagnostic method is of great significance. Here, we designed a magnetic responsive structural color core-shell hydrogel microcarrier as a novel platform for a high-throughput detection of a variety of cardiovascular biomarkers. The composite hydrogel shell was formed from methacrylated gelatin, acrylic acid, and poly(ethylene glycol diacrylate), and the core silica photonic crystals acted as a detector. Fe₃O₄ nanoparticles were infused into the void of the core-shell structure to impart magnetic response properties to the encoded carrier. The findings indicated that our method possessed high sensitivity and reliable specificity in the high-throughput detection of AMI-related biomarkers Myo, cTnI, and BNP. In addition, the developed method not only showed good specificity and high sensitivity in clinical samples but also was comparable to the clinical gold standard method. Therefore, the magnetic response structural color core-shell hydrogel carriers were regarded as a potential approach to detect some AMI disease-related biomarkers.

Multiplex optical bioassays for food safety analysis: Toward on-site detection

Food safety analysis plays a significant role in controlling food contamination and supervision. In recent years, multiplex optical bioassays (MOBAs) have been widely applied to analyze multiple hazards due to their efficiency and low cost. However, due to the challenges such as multiplexing capacity, poor sensitivity, and bulky instrumentation, the further application of traditional MOBAs in food screening has been limited. In this review, effective strategies regarding food safety MOBAs are summarized, such as spatial-resolution modes performed in multi-T lines/dots strips or arrays of strip/microplate/microfluidic chip/SPR chip and signal-resolution modes employing distinguishable colorimetric/luminescence/fluorescence/surface plasma resonance/surface-enhanced Raman spectrum as signal tags. Following this, new trends on how to design engineered sensor architecture and exploit distinguishable signal reporters, how to improve both multiplexing capacity and sensitivity, and how to integrate these formats into smartphones so as to be mobile are summarized systematically. Typically, in the case of enhancing multiplexing capacity and detection throughput, microfluidic array chips with multichannel architecture would be a favorable approach to overcome the spatial and physical limitations of immunochromatographic assay (ICA) test strips. Moreover, noble metal nanoparticles and single-excitation, multiple-emission luminescence nanomaterials hold great potential in developing ultrasensitive MOBAs. Finally, the exploitation of innovative multiplexing strategy hybridized with powerful and widely available smartphones opens new perspectives to MOBAs. In future, the MOBAs should be more sensitive, have higher multiplexing capacity, and easier instrumentation.

Molecularly imprinted colloidal array with multi-boronic acid sites for glycoprotein detection under neutral pH

Glycoproteins play vital roles in living organisms and often serve as biomarkers for some disease. However, due to the low content of glycoprotein in biological fluids, selective detection of glycoproteins is still a challenging issue that needs to be addressed. In this study, molecularly imprinted colloidal array with multi-boronic acid sites for glycoprotein detection under physiological pH was proposed. Monodispersed glycoprotein imprinted particles (SiO₂@PEI/MIPs) was first prepared based on surface imprinting strategy using horseradish peroxidase (HRP) as template, and polyethyleneimine (PEI) was used to increase the number of boronic acid groups. The binding experiment indicated that the SiO₂@PEI/MIPs hold satisfactory adsorption capacity (1.41 μmol/g), rapid adsorption rate (40 min) and preferable selectivity toward HRP. Then the SiO₂@PEI/MIPs was assembled into close-packed colloidal array to construct a label free optical sensor (denoted as GICA). Benefiting from the high ordered photonic crystal structure, binding of HRP onto the GICA could be directly readout from the changes in structure color and diffracted wavelength. The structure color of the GICA changed from bright blue to yellow with the diffraction wavelength red shifted 59 nm when the HRP concentration increased from 2.5 to 15 μmol/L. Importantly, the GICA was capable of detecting HRP from human serum samples. All those results indicated the potential of the GICA for naked-eye detection of glycoprotein.

Photonics in nature and bioinspired designs: sustainable approaches for a colourful world

Biological systems possess nanoarchitectures that have evolved for specific purposes and whose ability to modulate the flow of light creates an extraordinary diversity of natural photonic structures. In particular, the striking beauty of the structural colouration observed in nature has inspired technological innovation in many fields. Intense research has been devoted to mimicking the unique vivid colours with newly designed photonic structures presenting stimuli-responsive properties, with remarkable applications in health care, safety and security. This review highlights bioinspired photonic approaches in this context, starting by presenting many appealing examples of structural colours in nature, followed by describing the versatility of fabrication methods and designed coloured structures. A particular focus is given to optical sensing for medical diagnosis, food control and environmental monitoring, which has experienced a significant growth, especially considering the advances in obtaining inexpensive miniaturized systems, more reliability, fast responses, and the use of label-free layouts. Additionally, naturally derived biomaterials and synthetic polymers are versatile and fit many different structural designs that are underlined. Progress in bioinspired photonic polymers and their integration in novel devices is discussed since recent developments have emerged to lift the expectations of smart, flexible, wearable and portable sensors. The discussion is expanded to give emphasis on additional functionalities offered to related biomedical applications and the use of structural colours in new sustainable strategies that could meet the needs of technological development.

Recent advances in self-assemblies and sensing applications of colloidal photonic crystals

Colloidal photonic crystals (PCs), consisting of highly ordered monodisperse nanoparticles, have been carried out a great deal of research in recent decades due to the attributes of readable signal, easy modification and low cost. With these unique features, colloidal PCs have also gradually become a focus of candidates applied in sensing fields. In this review, an overview of recent advances in colloidal PCs including self-assemblies and sensing applications is illustrated. With respect to the development in self-assemblies of colloidal PCs, the review concentrates on the summary of responsive mechanisms, detection methods, responsive materials, unit cells and fabrication methods. In terms of advances in sensing application of colloidal PCs, various types of sensors are summarized based on the kinds and applications of target analytes. Furthermore, the current limitations and potential future directions of colloidal PCs in self-assemblies and sensing areas are also discussed.

Glutathione-capped Syzygium cumini carbon dot-amalgamated agarose hydrogel film for naked-eye detection of heavy metal ions

Development of a facile and sensitive analytical tool for the detection of heavy metal ions is still a challenging task because of interference from other chemical species. In this work, glutathione (GSH)-capped Syzygium cumini carbon dots (CDs) have been integrated with agarose hydrogel film and used as an amalgamated solid probe for sensing of different metal ions (Pb2+, Fe3+, and Mn2+). The synthesis of a solid sensing platform is based on the electrostatic interactions between GSH-capped Syzygium cumini CDs and agarose hydrogel. The developed hydrogel-based solid probe exhibited good linearities with the concentration ranges of metal ions from 0.005 to 0.075, 0.0075 to 0.1, and 0.0075 to 0.1 mM with detection limits of 1.3, 2.5, and 2.1 μM for Pb2+, Fe3+, and Mn2+ ions, respectively.

Microfluidic Platforms toward Rational Material Fabrication for Biomedical Applications

The emergence of micro/nanomaterials in recent decades has brought promising alternative approaches in various biomedicine-related fields such as pharmaceutics, diagnostics, and therapeutics. These micro/nanomaterials for specific biomedical applications shall possess tailored properties and functionalities that are closely correlated to their geometries, structures, and compositions, therefore placing extremely high demands for manufacturing techniques. Owing to the superior capabilities in manipulating fluids and droplets at microscale, microfluidics has offered robust and versatile platform technologies enabling rational design and fabrication of micro/nanomaterials with precisely controlled geometries, structures and compositions in high throughput manners, making them excellent candidates for a variety of biomedical applications. This review briefly summarizes the progress of microfluidics in the fabrication of various micro/nanomaterials ranging from 0D (particles), 1D (fibers) to 2D/3D (film and bulk materials) materials with controllable geometries, structures, and compositions. The applications of these microfluidic-based materials in the fields of diagnostics, drug delivery, organs-on-chips, tissue engineering, and stimuli-responsive biodevices are introduced. Finally, an outlook is discussed on the future direction of microfluidic platforms for generating materials with superior properties and on-demand functionalities. The integration of new materials and techniques with microfluidics will pave new avenues for preparing advanced micro/nanomaterials with enhanced performance for biomedical applications.

Fluorescent Sensors for the Detection of Heavy Metal Ions in Aqueous Media

Due to the risks that water contamination implies for human health and environmental protection, monitoring the quality of water is a major concern of the present era. Therefore, in recent years several efforts have been dedicated to the development of fast, sensitive, and selective sensors for the detection of heavy metal ions. In particular, fluorescent sensors have gained in popularity due to their interesting features, such as high specificity, sensitivity, and reversibility. Thus, this review is devoted to the recent advances in fluorescent sensors for the monitoring of these contaminants, and special focus is placed on those devices based on fluorescent aptasensors, quantum dots, and organic dyes.