Journal of Materials Chemistry B top picks web collection: “seeing the unseen: advances in bioimaging and biosensors”

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Abstract

Xiaogang Qu introduces a Journal of Materials Chemistry B Top Picks web collection on advances in bioimaging and biosensors (http://rsc.li/bioimaging).

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Xiaogang Qu

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In recent years, functional materials-based bioimaging and biosensors have achieved significant progress in the diagnosis and prognosis of diseases via visualization, characterization, and measurement of biological processes. Within these, nanomaterials have revealed unparalleled potential in personalized treatment, early detection, point-of-care, and accurate diagnosis. Nanoprobes capable of “sensing and imaging” or “sensing and treating” have been successfully developed. These well-designed nanoparticles can not only provide detailed disease information in an intact system and give comprehensive statistical results in experimental or clinical situations, but also monitor curative effects and optimize drug dosages.

For bioimaging, various non-invasive advanced materials-based techniques including computed tomography (CT), ultrasound (US), magnetic resonance imaging (MRI), optical imaging, single photon-emission computed tomography (SPECT), and positron emission tomography (PET) have become powerful diagnostic tools. For example, fluorescent nanodots modified with peptides and antibodies have been used as targeted contrast agents (CA) for optical imaging and iron oxide-based magnetic nanoparticles have been considered as the most well-known examples for MRI and are being used in clinical trials.

Due to their suitable K-edge energy, located within the higher-energy region of the X-ray spectrum, and high abundance on earth, a series of lanthanide-based nanomaterials with excellent contrast efficiency have been prepared and utilized as contrast agents in 2D X-ray imaging and 3D CT imaging. Moreover, hybrid lanthanide-based nanostructures with controlled size as well as unique magnetic and optical behaviors have offered great opportunities for nanoparticulate CAs in MRI and up-conversion fluorescence imaging.

However, information obtained from single-modality biomedical imaging cannot satisfy the high requirements for efficiency and accuracy due to instrument limitations. For this reason, multifunctional nanoparticles for multi-modal biomedical imaging have emerged. For example, porphyrin–phospholipid-coated up-conversion nanoparticles have been applied as nanoparticulate CAs for hexamodal imaging and ultrathin PEGylated WO_2.72 nanosheets have been used as four-modality nanoparticulate CAs for the gastrointestinal (GI) tract.

For practical clinical usages, a systemic toxicity evaluation of these nanoparticles has to be thoroughly studied. The future of modern nanomedicine lies in this multifunctional nanoplatform combined with imaging functionality and therapeutic components. Towards this ultimate goal, all-in-one nanoplatforms can specifically allow for the efficient delivery of a gene/drug in vivo, as well as monitoring the delivery efficiency and the therapeutic efficacy via various non-invasive imaging modalities.

With the rapid advances in nanotechnology, nanomaterials-based biosensors are leading to the development of biosensing in various fields. Smart sensing platforms have been demonstrated with high sensitivity and selectivity for the detection of different kinds of analyte, such as small molecules (H₂O₂, glucose, dopamine, cholesterol), metal ions (Zn²⁺, Cu²⁺, Pb²⁺, Hg²⁺), biomacromolecules (proteins, DNA, RNA, enzymes), and even cells and bacteria. The concept, such as “sensing and treating” and logic operation, has been employed in biosensing and applied for healthcare, disease diagnosis and environmental applications.

Besides fluorescent and electrochemical techniques, other sensing assays based on surface-enhanced Raman spectroscopy (SERS), mass spectroscopy (MS), surface plasmon resonance (SPR) and various microscopies (TEM, SEM, AFM) also play important roles in the biosensing field. Nevertheless, signal amplification is a generally effective and widely used strategy for ultralow detection. A variety of signal amplification strategies (i.e. DNA amplification, enzyme amplification and nanomaterials-based amplification) have been applied in the detection of DNA, protein, cells and other important biomolecules.

For the construction of nanomaterial-based signal amplification biosensors, the following factors have been proven to be crucial: (i) nanomaterials should have good biocompatibility, which can be achieved by grafting biomolecules onto the surface of nanomaterials; (ii) the recognition mechanism of biomolecules with the surface of nanomaterials should be well studied; (iii) different types of nanomaterial with diverse properties can be used simultaneously. Nanomaterials possess unique characteristics and properties including superparamagnetic, fluorescent and electrical properties as well as specific surface chemistries. Thus, combination of different nanomaterials with their special properties can offer a synergetic multifunctional platform. The system can possess the abilities of sensing, imaging and treating, thereby accomplishing simultaneous diagnosis and therapy.

In summary, bioimaging and biosensors have made significant breakthroughs, and many interesting results have been published in this exciting field. Journal of Materials Chemistry B is an interdisciplinary journal, covering all aspects of the production, properties or applications of materials for healthcare and biomedicine, materials at the biointerface, biomimetics and bio-inspired or natural materials.

This Top Picks web collection (http://rsc.li/bioimaging) entitled “Seeing the unseen: advances in bioimaging and biosensors” highlights Journal of Materials Chemistry B's most outstanding papers in functional materials-based bioimaging and biosensing and their applications in early detection and prognosis of diseases and healthcare via visualization, characterization, and monitoring of important biological events.

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