Lanthanide-doped upconversion nanoparticles (UCNPs) have shown promise in biomedical applications. However, as the UCNPs are normally capped with hydrophobic ligands, it remains challenging to prepare biocompatible UCNPs with specific molecular recognition capabilities. We herein report an exceptionally simple strategy to prepare uniform DNA-modified upconversion nanoparticles (DNA-UCNPs) as versatile bioprobes. The approach can directly convert as-prepared hydrophobic UCNPs into water-soluble DNA-UCNPs without any chemical modification of UCNPs or oligonucleotides. Furthermore, DNA molecules on the DNA-UCNPs retain their biorecognition ability, allowing programmable assembly of hybrid nanostructures. More importantly, we show that these DNA-UCNPs are capable of crossing cell membranes without the need of transfection agents, and their use as agents for bioimaging and DNA delivery are also demonstrated. Finally, DNA aptamer-conjugated UCNPs can be readily used for targeted imaging of cancer cells.

A general and versatile biomimetic approach to synthesize water dispersible and functionalizable upconverting nanoparticles (UCNPs) for selective imaging of live cancer cells is reported. The approach involves coating the surface of UCNPs with a monolayer of phospholipids containing different functional groups, allowing for conjugation of many molecules for a wide range of applications in fields such as bioinspired nanoassembly, biosensing, and bio-medicine.

Spatiotemporal control over the delivery of therapeutic agents is an outstanding challenge to cancer treatment. By taking advantage of recent advances in DNA aptamer biology and mesoporous silica nanotechnology, we report a general approach to design and fabricate controlled release drug delivery systems that are able to effectively target cancer cells. Specifically, polyvalent mesoporous silica nanocarriers-aptamer bioconjugates were constructed; the high-surface-area nanoporous core allowed high drug loading and the surface-conjugated aptamer facilitated the nanoparticle targeting of nucleolin overexpressed MCF-7 cells. The efficient cancer-cell-specific fluorescent imaging and drug delivery of the bioconjugates outline the great potential for therapeutic applications.

Aptamers, single-stranded nucleic acids that can selectively bind to various target molecules, have been widely used for constructing biosensors. A major challenge in this field, however, is direct sensing of analytes in complex biological media such as undiluted serum. While progress has been made in developing inhomogeneous assay by using a pre-separation step to wash away the interferences within serum, a facile strategy for direct detection of targets in homogenous unprocessed serum is highly desired. We herein report a turn-on luminescent aptamer biosensor for the direct detection of adenosine in undiluted and unprocessed serum, by taking advantage of a terbium chelate complex with long luminescence lifetime to achieve time-resolved detection. The sensor exhibits a detection limit of 60 µM adenosine while marinating excellent selectivity that is comparable to those in buffer. The approach demonstrated here can be applied for direct detection and quantification of a broad range of analytes in biological media by using other aptamers.

We report a novel strategy for regiospecific hetero-assembly of DNA-modified gold nanoparticles (DNA-AuNPs) onto upconversion nanoparticles (UCNPs) into hybrid lab-on-a-particle systems. The DNA-AuNPs have been assembled onto the hexagonal plate-like UCNPs with well-regulated stoichiometry and controlled organization onto the different facets of UCNP, forming various addressable superstructures. The fine-tuning of stoichiometry and organization is realized by biorecognition specificity of DNA toward specific crystal facets of UCNPs. Such a hetero-assembled DNA-AuNP/UCNP system maintains both plasmonic resonance of AuNPs and fluorescent properties of UCNPs, allowing targeted dual-modality imaging of cancer cells using an aptamer.

A smart drug delivery system with cancer cell targeting and bioresponsive controlled drug release has been constructed by taking advantage of the protein-capped mesoporous nanovalve and a DNA aptamer.

We describe a method of creating graphene–DNAzyme junctions capable of directly detecting paramagnetic Cu2+ with femtomolar sensitivity and high selectivity.

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