Detection of chemical and biological agents plays a fundamental role in biomedical, forensic and environmental sciences1–4 as well as in anti bioterrorism applications.5–7 The development of highly sensitive, cost effective, miniature sensors is therefore in high demand which requires advanced technology coupled with fundamental knowledge in chemistry, biology and material sciences.8–13

In general, sensors feature two functional components: a recognition element to provide selective/specific binding with the target analytes and a transducer component for signaling the binding event. An efficient sensor relies heavily on these two essential components for the recognition process in terms of response time, signal to noise (S/N) ratio, selectivity and limits of detection (LOD).14,15 Therefore, designing sensors with higher efficacy depends on the development of novel materials to improve both the recognition and transduction processes. Nanomaterials feature unique physicochemical properties that can be of great utility in creating new recognition and transduction processes for chemical and biological sensors15–27 as well as improving the S/N ratio by miniaturization of the sensor elements.28

Gold nanoparticles (AuNPs) possess distinct physical and chemical attributes that make them excellent scaffolds for the fabrication of novel chemical and biological sensors (Figure 1).29–36 First, AuNPs can be synthesized in a straightforward manner and can be made highly stable. Second, they possess unique optoelectronic properties. Third, they provide high surface-to-volume ratio with excellent biocompatibility using appropriate ligands.30 Fourth, these properties of AuNPs can be readily tuned varying their size, shape and the surrounding chemical environment. For example, the binding event between recognition element and the analyte can alter physicochemical properties of transducer AuNPs, such as plasmon resonance absorption, conductivity, redox behavior, etc. that in turn can generate a detectable response signal. Finally, AuNPs offer a suitable platform for multi-functionalization with a wide range of organic or biological ligands for the selective binding and detection of small molecules and biological targets.30–32,36 Each of these attributes of AuNPs has allowed researchers to develop novel sensing strategies with improved sensitivity, stability and selectivity. In the last decade of research, the advent of AuNP as a sensory element provided us a broad spectrum of innovative approaches for the detection of metal ions, small molecules, proteins, nucleic acids, malignant cells, etc. in a rapid and efficient manner.37



Figure 1

Physical properties of AuNPs and schematic illustration of an AuNP-based detection system.



In this current review, we have highlighted the several synthetic routes and properties of AuNPs that make them excellent probes for different sensing strategies. Furthermore, we will discuss various sensing strategies and major advances in the last two decades of research utilizing AuNPs in the detection of variety of target analytes including metal ions, organic molecules, proteins, nucleic acids, and microorganisms.

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Gold nanoparticles in chemical and biological sensing.

This Perspective explores and explains the fundamental dogma of nanoparticle delivery to tumours and answers two central questions: ‘how many nanoparticles accumulate in a tumour?’ and ‘how does this number affect the clinical translation of nanomedicines?’

/pdf/analysis-of-nanoparticle-delivery-to-tumours-kovi4y80u2.pdf

Analysis of nanoparticle delivery to tumours

Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Sasidharan Swarnalatha Lucky,†,§ Khee Chee Soo,‡ and Yong Zhang*,†,§,∥ †NUS Graduate School for Integrative Sciences & Engineering (NGS), National University of Singapore, Singapore, Singapore 117456 ‡Division of Medical Sciences, National Cancer Centre Singapore, Singapore, Singapore 169610 Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore, Singapore 117576 College of Chemistry and Life Sciences, Zhejiang Normal University, Zhejiang, P. R. China 321004

Nanoparticles in photodynamic therapy.

Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1–3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the s...

Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities

1.1. Significance of IVDs in the Clinic
IVD test is a crucial component of clinical care that performs a diagnostic test on biological samples that have been taken from a living body, such as blood, urine, and tissue.1 Such tests are usually performed to determine or confirm the presence of disease in an individual. “In vitro” literally means “within the glass”, which indicates that the test was historically conducted in glass test tubes. In contrast, in vivo tests, literally “within the living”, are conducted within a whole, living organism including human body.2 IVD tests have received much public attention because of their distinct features in the medical profession. First, IVD tests do not interact with the human body directly, making such diagnosis accessible without invasive surgeries and thus saving a great deal of suffering. Second, the procedures of IVDs are performed on samples rather than human body, avoiding the possible biological safety problems on patients that often take place in the in vivo diagnostics. Third, an IVD test can quickly provide valuable information on a patient’s healthcare conditions. On the basis of the information, physicians or patients are able to make a timely decision for patient care or treatment. Fourth, the application of IVDs enables early diagnosis and makes treatment of serious diseases easier. Generally, the cost of early testing is much lower than that of the later on extensive treatment. Last, IVDs play a particularly vital role in remote settings for managing outbreaks of acute infectious diseases, where effective but simple diagnostic systems are highly desirable. These features make IVDs unique and of great importance among medical technologies.

Gold Nanoparticles for In Vitro Diagnostics

Chlorin e6 conjugated gold nanostars (GNS-PEG-Ce6) are used to perform simultaneous photodynamic/plasmonic photothermal therapy (PDT/PPTT) upon single laser irradiation. The early-phase PDT effect is coordinated with the late-phase PPTT effect to obtain synergistic anticancer efficiency. The prepared GNS-PEG-Ce6 shows excellent water dispersibility, good biocompatibility, enhanced cellular uptake and remarkable anticancer efficiency upon irradiation in vivo.

Single continuous wave laser induced photodynamic/plasmonic photothermal therapy using photosensitizer-functionalized gold nanostars.

In recent years, gold nanoparticles (AuNPs) have drawn considerable research attention in the fields of catalysis, drug delivery, imaging, diagnostics, therapy and biosensors due to their unique optical and electronic properties. In this review, we summarized recent advances in the development of AuNP-based colorimetric and fluorescent assays for ions including cations (such as Hg2+, Cu2+, Pb2+, As3+, Ca2+, Al3+, etc) and anions (such as NO2−, CN−, PF6−, F−, I−, oxoanions), and small organic molecules (such as cysteine, homocysteine, trinitrotoluene, melamine and cocaine, ATP, glucose, dopamine and so forth). Many of these species adversely affect human health and the environment. Moreover, we paid particular attention to AuNP-based colorimetric and fluorescent assays in practical applications.

Gold nanoparticles for the colorimetric and fluorescent detection of ions and small organic molecules.

This report presents a highly sensitive, rhodamine B-covered gold nanoparticle (RB-AuNP) -based assay with dual readouts (colorimetric and fluorometric) for detecting organophosphorus and carbamate pesticides in complex solutions. The detection mechanism is based on the fact that these pesticides can inhibit the activity of acetylcholinesterase (AChE), thus preventing the generation of thiocholine (which turns the RB-AuNP solutions blue and unquenches the fluorescence of RB simultaneously). The color of the RB-AuNP solution remains red and the fluorescence of RB remains quenched. By use of this dual-readout assay, the lowest detectable concentrations for several kinds of pesticides including carbaryl, diazinon, malathion, and phorate were measured to be 0.1, 0.1, 0.3, and 1 μg/L, respectively, all of which are much lower than the maximum residue limits (MRL) as reported in the European Union pesticides database as well as those from the U.S. Department Agriculture (USDA). This assay allows detection of pe...

A Highly Sensitive, Dual-Readout Assay Based on Gold Nanoparticles for Organophosphorus and Carbamate Pesticides

Core-shell nanoparticles (NPs) with lipid shells and varying water content and rigidity but with the same chemical composition, size, and surface properties are assembled using a microfluidic platform. Rigidity can dramatically alter the cellular uptake efficiency, with more-rigid NPs able to pass more easily through cell membranes. The mechanism accounting for this rigidity-dependent cellular uptake is revealed through atomistic-level simulations.

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Dingbin Liu

Papers

Gold Nanoparticles for In Vitro Diagnostics

Single continuous wave laser induced photodynamic/plasmonic photothermal therapy using photosensitizer-functionalized gold nanostars.

Gold nanoparticles for the colorimetric and fluorescent detection of ions and small organic molecules.

A Highly Sensitive, Dual-Readout Assay Based on Gold Nanoparticles for Organophosphorus and Carbamate Pesticides

Tunable Rigidity of (Polymeric Core)–(Lipid Shell) Nanoparticles for Regulated Cellular Uptake