Application of aptamer functionalized nanomaterials in targeting therapeutics of typical tumors

Cancer is a major cause of human death all over the world. Traditional cancer treatments include surgery, radiotherapy, chemotherapy, immunotherapy, and hormone therapy. Although these conventional treatment methods improve the overall survival rate, there are some problems, such as easy recurrence, poor treatment, and great side effects. Targeted therapy of tumors is a hot research topic at present. Nanomaterials are essential carriers of targeted drug delivery, and nucleic acid aptamers have become one of the most important targets for targeted tumor therapy because of their high stability, high affinity, and high selectivity. At present, aptamer-functionalized nanomaterials (AFNs), which combine the unique selective recognition characteristics of aptamers with the high-loading performance of nanomaterials, have been widely studied in the field of targeted tumor therapy. Based on the reported application of AFNs in the biomedical field, we introduce the characteristics of aptamer and nanomaterials, and the advantages of AFNs first. Then introduce the conventional treatment methods for glioma, oral cancer, lung cancer, breast cancer, liver cancer, colon cancer, pancreatic cancer, ovarian cancer, and prostate cancer, and the application of AFNs in targeted therapy of these tumors. Finally, we discuss the progress and challenges of AFNs in this field.

Hierarchical nanomaterials via biomolecular self-assembly and bioinspiration for energy and environmental applications

Bioinspired synthesis offers potential green strategies to build highly complex nanomaterials by utilizing the unique nanostructures, functions, and properties of biomolecules, in which the biomolecular recognition and self-assembly processes play important roles in tailoring the structures and functions of bioinspired materials. Further understanding of biomolecular self-assembly for inspiring the formation and assembly of nanoparticles would promote the design and fabrication of functional nanomaterials for various applications. In this review, we focus on recent advances in bioinspired synthesis and applications of hierarchical nanomaterials based on biomolecular self-assembly. We first discuss biomolecular self-assembly towards biological nanomaterials, in which the mechanisms and ways of biomolecular self-assembly as well as various self-assembled biomolecular nanostructures are demonstrated. Secondly, the bioinspired synthesis strategies including molecule-molecule interaction, molecule-material recognition, molecule-mediated nucleation and growth, and molecule-mediated reduction/oxidation are introduced and discussed. Meanwhile, typical examples and discussions on how biomolecular self-assembly inspires the formation of hierarchical hybrid nanomaterials are presented. Finally, the applications of bioinspired nanomaterials in biofuel cells, light-harvesting systems, batteries, supercapacitors, catalysis, water/air purification, and environmental monitoring are presented and discussed. We believe that this review will be very helpful for readers to understand the self-assembly of biomolecules and the biomimetic/bioinspired strategies for synthesizing hierarchical nanomaterials on the one hand, and on the other hand to design novel materials for extended applications in nanotechnology, materials science, analytical science, and biomedical engineering.

A fundamental study of photoluminescence modulation from DNA-wrapped single-walled carbon nanotubes

In this study, we investigated the interaction of base sequence-assigned single-stranded DNA (ssDNA) molecules with the surfaces of single-walled carbon nanotube (SWNT)-thymine (T30)/cytosine (C30) hybrids (T30/C30-SWNT), by measuring the modulation of near-infrared (NIR) photoluminescence (PL). Significant PL shifts were observed when T30/C30-SWNTs were reacted with 30-mers of adenine (A30)/guanine (G30). In contrast, when non-complementary ssDNA was used, no significant energy shift was observed in the PL modulation except when T30-SWNTs were reacted with G30. Furthermore, atomic force microscopy (AFM) measurements revealed that the average heights of the T30-SWNTs and C30-SWNTs, after reaction with A30 were 2 ± 0.6 and 1.1 ± 0.3 nm, respectively. This result was in good agreement with the results of PL measurements. Our data reveal that DNA hybridization could be detected by measuring PL from SWNTs, without the use of fluorescent molecules. This leads to the possibility of developing nanotube-based photoelectric conversion or optical switch devices driven by organic molecules.

Metal ion detection using functional nucleic acids and nanomaterials

Metal ion detection is critical in a variety of areas. The past decade has witnessed great progress in the development of metal ion sensors using functional nucleic acids (FNAs) and nanomaterials. The former has good recognition selectivity toward metal ions and the latter possesses unique properties for enhancing the performance of metal ion sensors. This review offers a summary of FNA- and nanomaterial-based metal ion detection methods. FNAs mainly include DNAzymes, G-quadruplexes, and mismatched base pairs and nanomaterials cover gold nanoparticles (GNPs), quantum dots (QDs), carbon nanotubes (CNTs), and graphene oxide (GO). The roles of FNAs and nanomaterials are introduced first. Then, various methods based on the combination of different FNAs and nanomaterials are discussed. Finally, the challenges and future directions of metal ion sensors are presented.

Novel carbon nanotube (CNT)-based ultrasensitive sensors for trace mercury(II) detection in water: A review

Infamous for "Mad hatter syndrome" and "Minamata disease", mercury (Hg) is ranked high on the Agency for Toxic Substances and Disease Registry's priority list of hazardous substances for its potent neurologic, renal, and developmental toxicities. Most typical exposures are via contaminated water and food. Although regulations and advisories are exercised at various levels, Hg pollution from both natural and anthropogenic sources has remained a major public health and safety concern. Rapid detection of solvated aqueous Hg²⁺ ions at low levels is critical for immediate response and protection of those who are vulnerable (young children, pregnant and breast-feeding women) to acute and chronic exposures to Hg²⁺. Various types of sensors capable of detecting Hg in water have been developed. In particular, the novel use of engineered carbon nanotubes (CNTs) has garnered attention due to their specificity and sensitivity towards Hg²⁺ detection in solution. In this focused review, we describe the sensitivity, selectivity and mechanisms of Hg²⁺ ion sensing at trace levels by employing CNT-based various sensor designs, and appraise the open literature on the currently applied and "proof-of-concept" methods. Five different types of CNT-based sensor systems are described: potentiometric, DNA-based fluorescence, surface plasmon resonance (SPR), colorimetric, and stripping voltammetric assays. In addition, the recognized merits and shortcomings for each type of electrochemical sensors are discussed. The knowledge from this succinct review shall guide the development of the next generation CNT-based biochemical sensors for rapid Hg²⁺ detection in the environment, which is a significant first step towards human health risk analysis of this legacy toxicant.

Nanomaterial-enabled Rapid Detection of Water Contaminants

Water contaminants, e.g., inorganic chemicals and microorganisms, are critical metrics for water quality monitoring and have significant impacts on human health and plants/organisms living in water. The scope and focus of this review is nanomaterial-based optical, electronic, and electrochemical sensors for rapid detection of water contaminants, e.g., heavy metals, anions, and bacteria. These contaminants are commonly found in different water systems. The importance of water quality monitoring and control demands significant advancement in the detection of contaminants in water because current sensing technologies for water contaminants have limitations. The advantages of nanomaterial-based sensing technologies are highlighted and recent progress on nanomaterial-based sensors for rapid water contaminant detection is discussed. An outlook for future research into this rapidly growing field is also provided.

Selective detection and quantification of carbon nanotubes in soil

Carbon nanotubes (CNTs) have been widely applied in many industrial fields. As world production of CNTs increases, the risk of environmental exposure to CNTs also increases. Therefore, to evaluate the impact on the environment, many cell and animal studies have reported on the toxicity of CNTs. It is important to determine the degree of contamination of CNTs in soil and to find the pollution pathways for assessment of the environmental toxicity of CNTs. However, selective detection methods for CNTs in soil or water have rarely been reported. In the present study, a novel technique was developed to quantify the amount of CNTs in soil mixtures using fluorescent SYBR Green I dye after isolation of the CNTs with specific DNA oligomers. As a result, a limit of detection of CNTs in soil was obtained in the range of 250 ppb. This limit can easily be extended to the level of 10 ppb using magnetic well plates with a greater capacity. This method also worked well in the presence of graphene oxide and could be applied to the detection of CNTs in a variety of surroundings (e.g., fish and other tissues).

Functional nucleic acid-based sensors for heavy metal ion assays

Heavy metal contaminants such as lead ions (Pb(2+)), mercury ions (Hg(2+)) and silver ions (Ag(+)) can cause significant harm to humans and generate enduring bioaccumulation in ecological systems. Even though a variety of methods have been developed for Pb(2+), Hg(2+) and Ag(+) assays, most of them are usually laborious and time-consuming with poor sensitivity. Due to their unique advantages of excellent catalytic properties and high affinity for heavy metal ions, functional nucleic acids such as DNAzymes and aptamers show great promise in the development of novel sensors for heavy metal ion assays. In this review, we summarize the development of functional nucleic acid-based sensors for the detection of Pb(2+), Hg(2+) and Ag(+), and especially focus on two categories including the direct assay and the amplification-based assay. We highlight the emerging trends in the development of sensitive and selective sensors for heavy metal ion assays as well.

Layered MnO₂ nanosheet as a label-free nanoplatform for rapid detection of mercury(II)

A layered MnO2 nanosheet was established as a label-free fluorescent sensing platform for a rapid, sensitive and low-cost detection of mercury(II) ion in aqueous solution based on the target-induced conformational change of mercury-specific oligonucleotide (MSO) and the interactions between the fluorogenic MSO probe and MnO2 nanosheet.

Nanomaterial-based approaches for the detection and speciation of mercury

Detection and speciation of Hg through the T–Hg–T coordination, Hg–S and/or Hg–Au/Ag interactions based colorimetric or fluorescent changes.

Sensitive mutant DNA biomarker detection based on magnetic nanoparticles and nicking endonuclease assisted fluorescence signal amplification

Amplified fluorescence target DNA detection was developed combining nicking endonuclease assisted target recycling and magnetic nanoparticles with low background signal.

Label-free chemiresistive biosensor for mercury (II) based on single-walled carbon nanotubes and structure-switching DNA

Herein, we present a sensitive, selective, and facile label-free DNA functionalized single-walled carbon nanotube (SWNT)-based chemiresistive biosensor for the detection of Hg(2+). SWNTs were functionalized with Hg(2+) binding 15-bases long polyT oligonucleotide through covalent attachment using a bilinker molecule. The polyT was further hybridized with polyA to form a polyT-polyA duplex. When exposed to Hg(2+) the polyT-polyA duplex was dehybridized combined with switching of polyT structure, leading to change in resistance/conductance of the SWNT chemiresistor device. The device provided a significant response within 100 to 1000 nM of Hg(2+) concentration with a 6.72 × 10(-3) nM(-1) sensitivity.

Highly sensitive, selective, and rapid fluorescence Hg2+ sensor based on DNA duplexes of poly(dT) and graphene oxide

Coupling T base with Hg(2+) to form stable T-Hg(2+)-T complexes represents a new direction in detection of Hg(2+). Here a graphene oxide (GO)-based fluorescence Hg(2+) analysis using DNA duplexes of poly(dT) that allows rapid, sensitive, and selective detection is first reported. The Hg(2+)-induced T(15)-(Hg(2+))(n)-T(15) duplexes make T(15) unable to hybridize with its complementary A(15) labelled with 6'-carboxyfluorescein (FAM-A(15)), which has low fluorescence in the presence of GO. On the contrary, when T(15) hybridizes with FAM-A(15) to form double-stranded DNA because of the absence of Hg(2+), the fluorescence largely remains in the presence of GO. A linear range from 10 nM to 2.0 μM (R(2) = 0.9963) and a detection limit of 0.5 nM for Hg(2+) were obtained under optimal experimental conditions. Other metal ions, such as Al(3+), Ag(+), Ca(2+), Ba(2+), Mg(2+), Zn(2+), Mn(2+), Co(2+), Pb(2+), Ni(2+), Cu(2+), Cd(2+), Cr(3+), Fe(2+), and Fe(3+), had no significant effect on Hg(2+) detection. Moreover, the sensing system was used for the determination of Hg(2+) in river water samples with satisfactory results.