Cobalt oxyhydroxide modified with poly-β-cyclodextrin and a cyanine dye as a nanoplatform for two-photon imaging of ascorbic acid in living cells and tissue

Research progress of fluorescent composites based on cyclodextrins: Preparation strategies, fluorescence properties and applications in sensing and bioimaging

Fluorescence analysis has been regarded as one of the commonly used analytical methods because of its advantages of simple operation, fast response, low cost and high sensitivity. So far, various fluorescent probes, with noble metal nanoclusters, quantum dots, organic dyes and metal organic frameworks as representatives, have been widely reported. However, single fluorescent probe often suffers from some deficiencies, such as low quantum yield, poor chemical stability, low water solubility and toxicity. To overcome these disadvantages, the introduction of cyclodextrins into fluorescent probes has become a fascinating approach. This review (with 218 references) systematically covers the research progress of fluorescent composites based on cyclodextrins in recent years. Preparation strategies, fluorescence properties, response mechanisms and applications in sensing (ions, organic pollutants, bio-related molecules, temperature, pH) and bioimaging of fluorescent composites based on cyclodextrins are summarized in detail. Finally, the current challenges and future perspectives of these composites in relative research fields are discussed.

Multifunctional polysaccharide nanoprobes for biological imaging

Imaging and tracking biological targets or processes play an important role in revealing molecular mechanisms and disease states. Bioimaging via optical, nuclear, or magnetic resonance techniques enables high resolution, high sensitivity, and high depth imaging from the whole animal down to single cells via advanced functional nanoprobes. To overcome the limitations of single-modality imaging, multimodality nanoprobes have been engineered with a variety of imaging modalities and functionalities. Polysaccharides are sugar-containing bioactive polymers with superior biocompatibility, biodegradability, and solubility. The combination of polysaccharides with single or multiple contrast agents facilitates the development of novel nanoprobes with enhanced functions for biological imaging. Nanoprobes constructed with clinically applicable polysaccharides and contrast agents hold great potential for clinical translations. This review briefly introduces the basics of different imaging modalities and polysaccharides, then summarizes the recent progress of polysaccharide-based nanoprobes for biological imaging in various diseases, emphasizing bioimaging with optical, nuclear, and magnetic resonance techniques. The current issues and future directions regarding the development and applications of polysaccharide nanoprobes are further discussed.

In situ construction of a cobalt oxyhydroxide loaded pyrene-based fluorescent organic nanoprobe for bioimaging of endogenous ascorbic acid in living cells

A novel in situ strategy to fabricate CoOOH nanoflake-loaded pyrene-based FONs (denoted as PyFONs@CoOOH) as proof-of-concept of a sensing platform for direct bioimaging of endogenous AA in living cells.

Design a fluorometric aptasensor based on CoOOH nanosheets and carbon dots for simultaneous detection of lysozyme and adenosine triphosphate

Simultaneous detection of biomarkers and biomolecules with great analytical performance still is challenging. A simple fluorometric dual-functional aptasensor was designed to detect Lysozyme (LYS) and adenosine triphosphate (ATP) as models of a protein and a small molecule simultaneously. The sensing principle of the aptasensor is based on the interactions between cobalt oxyhydroxide CoOOH nanosheets as fluorescence quencher and carbon dots (CDs) as fluorophores. The aptamer labeled with CDs was able to assemble on CoOOH nanosheets and consequently, the fluorescence signal was quenched. With addition target analytes to the system, the aptamers folded around of targets with a strong and specific affinity. Therefore, the labeled aptamer with CDs was detached from CoOOH nanosheets and the fluorescence signal was restored. The fluorescence spectral overlap of these two CDs is the main limitation for the simultaneous analysis. The least squared support vector machine (LS-SVM) was applied to resolve this problem. Under optimal conditions, when LS-SVR was used, detection limits were found 4.0 and 1.8 nmol L^-1 for ATP and LYS. The parallel biosensor is capable of monitoring ATP and LYS levels in the biological samples with satisfactory results.

Two-photon imaging of aptamer-functionalized Copolymer/TPdye fluorescent organic dots targeted to cancer cells

Fluorescent organic dots (O-dots) recently have emerged as a new class of promising contrast reagents for two-photon fluorescence (TPF) imaging. However, most of these developed two-photon absorption (TPA) O-dots have no tumor-targeting group, which hampers their wide application for targeted tumor imaging. Herein, we fabricated Sgc8c aptamer-mediated TPA O-dots as a proof-of-concept of the sensing platform for targeted imaging in live cells or deep tissues. The O-dots composed of trans-4-[p-(N, N-diethylamino)styryl]-4'-(dimethyl amino) stilbene (DEAS) emerged as TPA organic emissive cores and encapsulation by using poly (methyl methacrylate-co-methacrylic acid) (PMMA-co-MAA) as polymeric encapsulating matrix to form DEAS/PMMA-co-MAA O-dots via a co-precipitation strategy. The obtained O-dots enabled an extremely high TPA absorption cross-section, bright two-photon fluorescence (excitation at 720 nm; emission at 412 nm and 434 nm), excellent cell-permeability and high penetration depth. Sgc8c aptamer, as a protein tyrosine kinase-7 (PTK7) receptor-targetable ligand, was further anchored on the surface of O-dots to obtain DEAS/PMMA-co-MAA@Sgc8c nanoprobes by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)-mediated coupling reaction. Guided by Sgc8c aptamer, DEAS/PMMA-co-MAA@Sgc8c nanoprobes could be rapidly internalized into target acute lymphoblastic leukemia cells (CEM) cells with high specificity and great efficiency. It was also performed that two-photon images of TPA nanoprobes exhibited high two-photon brightness not only in target CEM cells, but also in mouse liver tissue slices even a depth of up to 210 μm. In our perception, it is highly promising that this nanoprobe provides a valuable tool for in vivo targeted imaging.

The classification and application of cyclodextrin polymers: a review

After introducing the concept of cyclodextrin polymers, their classification and applications have been summarized.