Hydroxyapatite (HAp) is the main inorganic component of human bones and teeth. The doping of HAp nanocrystals plays an important role in tissue engineering, drug delivery, biomarkers and artificial bones. In this article, a postsynthetic metal ion exchange method was developed for doping hydroxyapatite (HAp) nanocrystals in organic solutions. It can be mono- or multi-ion doped with Mg2+, Sr2+, Zn2+, Mn2+, Fe3+ or Cu2+ etc., despite the significant radius variation of Ca2+ and doping ions. The doping ratio can be tuned in a wide range, e.g. Fe3+ of 0–20%, which is much higher than the ion exchange performed in aqueous solution. The structure and morphology of the HAp nanocrystals were preserved after postsynthetic doping, suggesting potential biological applications.

The fast-developing field of nanotechnology provides unprecedented opportunities for the increasing demands of biomedicine, especially for cancer diagnostics and treatment. Here, novel multifunctional zero-dimensional-two-dimensional (0D–2D) RGD-QD-MoS2 nanosheets (NSs) with excellent fluorescence, photothermal conversion, and cancer-targeting properties were successfully prepared by functionalizing single-layer MoS2 NSs with fluorescent quantum dots (QDs) and arginine–glycine–aspartic (RGD) containing peptides. By using RGD-QD-MoS2 NSs as a multifunctional theranostic agent, targeted fluorescent imaging and photothermal therapy (PTT) of human cervical carcinoma (HeLa) cells were achieved. Moreover, HeLa tumors in mouse models can be fluorescently imaged and completely eradicated by photothermal irradiation using a low power NIR laser, due to the effective accumulation of RGD-QD-MoS2 NSs at the tumor sites through the RGD-integrin targeting and the enhanced penetration and retention (EPR) effect. Without exhibiting any appreciable toxicity to treated cells or animals, RGD-QD-MoS2 NSs have been demonstrated as promising multifunctional theranostic agents for cancer imaging and therapy.

C60 and single-layer MoS2 nanocomposites were facilely prepared via a combined solvent transfer and surface deposition (STSD) method by templating C60 aggregates on 2D MoS2 nanosheets to construct hybrid van der Waals heterojunctions. The electronic property of the hybrid nanomaterials was investigated in a direct charge transport diode device configuration of ITO/C60–MoS2 nanocomposites/Al; rewritable nonvolatile resistive switching with low SET/RESET voltage (∼3 V), high ON/OFF resistance ratio (∼4 × 103), and superior electrical bistability (>104 s) of a flash memory behavior was observed. This particular electrical property of C60–MoS2 nanocomposites, not possessed by either C60 or MoS2 nanosheets, was supposed to be due to the efficiently established C60/MoS2 p–n nanojunction, which controls the electron tunneling via junction barriers modulated by electric-field-induced polarization. Thus, our 2D templating method through STSD is promising to massively allocate van der Waals p–n heterojunctions in 2D nanocomposites, opening a window for important insights into the charge transport across the interface of organic/2D-semiconductors.

Herein, we report a convenient approach to developing quantum dots (QDs)-based nanosensors for DNA and micro-RNA (miRNA) detection. The DNA-QDs conjugate was prepared by a ligand-exchange method. Thiol-labeled ssDNA is directly attached to the QD surface, leading to highly water-dispersible nanoconjugates. The DNA-QDs conjugate has the advantages of the excellent optical properties of QDs and well-controlled recognition properties of DNA and can be used as a nanoprobe to construct a nanosensor for nucleic acid detection. With the addition of a target nucleic acid sequence, the fluorescence intensity of QDs was quenched by an organic quencher (BHQ2) via Förster resonance energy transfer. This nanosensor can detect as low as 1 fM DNA and 10 fM miRNA. Moreover, the QDs-based nanosensor exhibited excellent selectivity. It not only can effectively distinguish single-base-mismatched and random nucleic sequences but also can recognize pre-miRNA and mature miRNA. Therefore, the nanosensor has high application potential for disease diagnosis and biological analysis.Keywords: DNA; FRET; micro-RNA; nanosensor; quantum dots;