Effect of aggregated silver nanoparticles on luminol chemiluminescence system and its analytical application

Nanomaterials for light-mediated therapeutics in deep tissue

Light-mediated therapeutics, including photodynamic therapy, photothermal therapy and light-triggered drug delivery, have been widely studied due to their high specificity and effective therapy. However, conventional light-mediated therapies usually depend on the activation of light-sensitive molecules with UV or visible light, which have poor penetration in biological tissues. Over the past decade, efforts have been made to engineer nanosystems that can generate luminescence through excitation with near-infrared (NIR) light, ultrasound or X-ray. Certain nanosystems can even carry out light-mediated therapy through chemiluminescence, eliminating the need for external activation. Compared to UV or visible light, these 4 excitation modes penetrate more deeply into biological tissues, triggering light-mediated therapy in deeper tissues. In this review, we systematically report the design and mechanisms of different luminescent nanosystems excited by the 4 excitation sources, methods to enhance the generated luminescence, and recent applications of such nanosystems in deep tissue light-mediated therapeutics.

Highly sensitive and simple colorimetric assay of hydrogen peroxide and glucose in human serum via the smart synergistic catalytic mechanism

Due to the own defects of natural enzymes, artificial simulated enzymes are always concerned. Here, the fabricated graphene oxide (GO)/AuNPs nanocomposite exhibits strong synergistic catalysis of peroxidase-mimicking enzymes in combination with the novel property of GO catalytic interface and AuNPs-mediated electron transfer. It can efficiently catalyze the oxidation of enzyme substrate TMB by hydrogen peroxide to form blue TMB oxide. Based on this, the rapid and highly sensitive colorimetric detection of hydrogen peroxide was achieved. Because of the wonderfully synergistic coupling catalysis from GO/AuNPs nanocomposites, the developed artificial enzyme has ultra-strong catalytic activity. For the detection of hydrogen peroxide, the detection limit of this colorimetric analysis is as low as 4.2 × 10^-8 M, which is about 1-2 orders of magnitude lower than that of the assays using other single nanoparticles as nanozymes. And it shows high sensitivity. The catalytic oxidation of the prepared nanocomposites to TMB can be completed in minutes, and the response is extremely fast. Combined with the reaction of glucose and glucose oxidase, the colorimetric analysis also realizes the rapid and highly sensitive detection of glucose in human serum. The research results infer that the smart synergy is an effective way to improve the catalytic activity of mimic enzyme. Together with its simplicity in preparation, the GO/AuNPs nanocomposite has excellent development potential in biomedical detection and biosensor design.

Cationic liposome-triggered luminol chemiluminescence reaction and its applications

Liposomes are spherical phospholipid bilayer vesicles. In the present study, we found that cationic liposomes made by (2,3-dioleoyloxy-propyl)-trimethylammonium (DOTAP) could enhance the luminol-H₂O₂ chemiluminescence (CL) reaction. Mechanism studies showed that the positive charge on the surface of liposomes plays an important role in the CL process. We speculated that the cationic liposomes with quaternary ammonium groups on the surface may be capable of catalyzing the decomposition of H₂O₂ leading to the formation of oxygen-related free radicals including ˙OH, ¹O₂, and O₂˙^-. The luminol anions tend to move close to the surface of the cationic liposomes and then to be oxidized by the oxidizing radical species which may be around the surface of cationic liposomes forming excited-state 3-aminophthalate* (3-APA*). When the 3-APA* returns to the ground state, an enhanced CL is observed. In addition, the single-strand DNA (ssDNA) showed a significant inhibition effect on the proposed CL reaction. The CL intensity decreased linearly with an increasing amount of DNA from 0.05 to 2 pmol. We assumed that the binding of ssDNA with cationic liposomes would neutralize the positive charge on the surface of liposomes and inhibit the catalytic activity of DOTAP cationic liposomes. Based on the ssDNA-inhibited luminol-H₂O₂-cationic liposome CL reaction, simple label-free CL sensing platforms were developed for the detection of sequence-specific DNA related to the hepatitis B virus (HBV) gene and for the detection of ATP (as a model analyte) using an anti-ATP aptamer as the recognition element.

Simple and rapid chemiluminescence aptasensor for Hg2+ in contaminated samples: A new signal amplification mechanism

Detection of ultralow concentration of heavy metal ion Hg²⁺ is important for human health protection and environment monitoring because of the gradual accumulation in environmental and biological fields. Herein, we report a convenient chemiluminescence (CL) biosensing platform for ultrasensitive Hg²⁺ detection by signal amplification mechanism from positively charged gold nanoparticles ((+)AuNPs). It is based on (+)AuNPs charge effect and aptamer conformation change induced by target to stimulate the generation of CL in the presence of H₂O₂ and luminol without high salt medium. Notably particularly, the typical problem of the high salt medium from (-) AuNPs system, like influencing aptamers' bind with target and hindering CL reaction can be effectively addressed through the direct introduction of (+)AuNPs. Therefore, the proposed biosensing exhibits a high sensitivity toward target Hg²⁺ with a detection limit of 16 pM, which is far below the limit (10nM) defined by the U.S. Environmental Protection Agency in drinkable water, and is about 10-fold lower than the previously reported aptamer-based assays for Hg²⁺. This sensing platform provides a simple, rapid, and cost-effective approach for label-free sensitive detection of Hg²⁺. Moreover, it is universal for the detection of other targets. Undoubtedly, such a direct utilizing of (+)AuNPs' charge effect will provide a new signal amplification way for label-free aptamer-based CL analysis.

A simple and rapid chemiluminescence aptasensor for acetamiprid in contaminated samples: Sensitivity, selectivity and mechanism

Ultralow concentration and selective detection of pesticide residue is important to evaluate the environmental and biological pollution and the threat to human health which single component pesticide can bring. Herein, we report an amplified chemiluminescence (CL) sensing platform for ultrasensitive and selective acetamiprid (widely used pesticide) detection. It is based on aptamer's high binding affinity to target and the relevance between AuNPs' morphology and its catalytic effect to stimulate the generation of CL in the presence of H2O2 and luminol. Moreover, AuNPs morphological slight change induced by aptamers' conformation during targets binding could lead to the significant change of catalytic properties. Therefore, the proposed sensing platform for pesticide residue exhibited a high sensitivity toward acetamiprid with a detection limit of 62pM, which was about 100-fold lower than that of other aptamer-based sensor for acetamiprid detection. Because of the intrinsic specificity of aptamer's recognization, this sensing platform has high selectivity. So, this sensing platform provides a label-free and cost-effective approach for sensitive and selective detection of single component pesticide residue. More importantly, this CL method was successfully used to determine acetamiprid in real contaminated samples.