Innovative phosphorus and nitrogen dual-doped hollow carbon dots (PNHCDs) have been fabricated for anticancer drug delivery and biological imaging. The functional groups of PNHCDs are introduced by simply mixing glucose, 1,2-ethylenediamine, and concentrated phosphoric acid. This is an automatic method without external heat treatment to rapidly produce large quantities of PNHCDs, which avoid high temperature, complicated operations, and long reaction times. The as-prepared PNHCDs possess small particle size, hollow structure, and abundant phosphate/hydroxyl/pyridinic/pyrrolic-like N groups, endowing PNHCDs with fluorescent properties, improving the accuracy of PNHCDs as an optical monitoring code both in vitro and in vivo. The investigation of PNHCDs as an anticancer drug nanocarrier for doxorubicin (DOX) indicates a better antitumor efficacy than free DOX owing to its enhanced nuclear delivery in vitro and tumor accumulation in vivo, which results in highly effective tumor growth inhibition and improved targeted therapy for cancer in clinical medicine.

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We report a versatile biosensing platform capable of achieving ultrasensitive detection of both small-molecule and macromolecular targets. The system features three components: reduced graphene oxide for its ability to adsorb single-stranded DNA molecules nonspecifically, DNA aptamers for their ability to bind reduced graphene oxide but undergo target-induced conformational changes that facilitate their release from the reduced graphene oxide surface, and rolling circle amplification (RCA) for its ability to amplify a primer-template recognition event into repetitive sequence units that can be easily detected. The key to the design is the tagging of a short primer to an aptamer sequence, which results in a small DNA probe that allows for both effective probe adsorption onto the reduced graphene oxide surface to mask the primer domain in the absence of the target, as well as efficient probe release in the presence of the target to make the primer available for template binding and RCA. We also made an observation that the circular template, which on its own does not cause a detectable level of probe release from the reduced graphene oxide, augments target-induced probe release. The synergistic release of DNA probes is interpreted to be a contributing factor for the high detection sensitivity. The broad utility of the platform is illustrated though engineering three different sensors that are capable of achieving ultrasensitive detection of a protein target, a DNA sequence and a small-molecule analyte. We envision that the approach described herein will find useful applications in the biological, medical, and environmental fields.

Activating room-temperature phosphorescence (RTP) emission in aqueous environments is a challenging feat because of the releasing of nonradiative decay pathways. Here, a design strategy was presented that effectively promotes the presence of RTP of carbon dots (CDs) in aqueous solutions by utilizing CDs and melamine to construct hydrogen-bonded networks to form a polymer (M-CDs). The obtained M-CDs not only enjoy an ultralong phosphorescence lifetime of 664 ms, but also relatively high quantum yield of 25% in an aqueous environment at 468 nm excitation. This is also a rare example of achieving RTP of CDs with a solid state in an aqueous environment. Further investigations reveal that the hydrogen-bonded networks are critical to the implementation of RTP in an aqueous environment. The existence of covalent bonds in CDs and melamine further stabilizes the hydrogen-bond skeleton and triplet state. Furthermore, the bound water formed inside the M-CDs also plays an indispensable role in stabilizing the RTP in the aqueous solution. Given the feature, the M-CDs are used to effectively implement double data encryption and decryption. In addition, this strategy is universal for most phosphorescence materials. This result will pave the way toward expanding RTP materials and their applications in aqueous environments.

Owing to their diverse properties, fluorescent carbon dots (CDs) have attracted more attention and present enormous potential in development of sensors, bioimaging, drug delivery, microfluidics, photodynamic therapy, light emitting diode, and so forth. Herein, a multifunctional sensing platform based on bright yellow fluorescent CDs (Y-CDs) was designed for the label-free detection of fluoroquinolones (FQs) and histidine (His). The Y-CDs with superior optical and biological merits including high chemical stability, good biocompatibility, and low cytotoxicity were simply synthesized via one-step hydrothermal treatment of o-phenylenediamine (o-PD) and 4-aminobutyric acid (GABA). The Y-CDs can be utilized to directly monitor the amount of FQs based on fluorescence static quenching owing to the specific interaction between FQs and Y-CDs. Then, the fluorescence of this system can be effectively recovered upon addition of His. The multifunctional sensing platform exhibited high sensitivity and selectivity toward three kinds of FQs and His with low detection limits of 17–67 and 35 nM, respectively. Benefiting from these outstanding characters, the Y-CDs were successfully employed for trace detection of FQs in real samples such as antibiotic tablets and milk products. Furthermore, the probe was also extended to cellular imaging. All of the above prove that this multifunctional sensing platform presents great prospect in multiple applications such as biosensing, biomedicine, disease diagnosis, and environmental monitoring.

Samples of polydisperse gold nanoclusters (AuNCs) protected with monolayers of N-acetyl-L-cysteine (NAC) have been chromatographically separated by a C18 column (4.6 mm x 250 mm) using a gradient elution program with a mobile phase of methanol (MeOH)/water containing tetrabutylammonium fluoride (Bu(4)N(+)F(-)) and sodium chloride. The effects of Bu(4)N(+)F(-) and MeOH on the separation have been investigated in detail. In conjunction with absorbance-based, fluorescence, and electrochemical detectors, the elution order of these water-soluble AuNCs is confirmed according to their core size in an ascending order. The onset oxidation potential closely follows the core size of AuNC. The separated fractions from high-performance liquid chromatography (HPLC) were collected and analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry to determine the number of Au atoms in the fractions. The sizes of AuNCs in some selected HPLC fractions were also assessed by transmission electron microscopy and high-resolution transmission electron microscopy. Photoluminescence spectra of the fractions show that the luminescent shift in the visible/near-infrared region does not follow with the core size of AuNC. More importantly, the proposed HPLC methodology has been successfully applied to analyze various polydisperse AuNC products synthesized from different gold-to-ligand mole ratios (Au/NAC) and reaction temperatures. The results confirm that larger Au/NAC and higher temperature will produce larger core size AuNCs products with narrower dispersity. In addition, AuNC samples obtained from various synthesis reaction times were analyzed by our HPLC methodology, demonstrating that the reaction's behavior follows the nucleation-growth-disintegration process.

Elucidating the intrinsic relationship between diseases and lipid droplet (LD) polarity remains a great challenge owing to the lack of the research on multiple disease models. Until now, the visualization of abnormal LD polarity in models of inflammation and clinical cancer patient samples has not been achieved. To meet the urgent challenge, we facilely synthesized a robust LD-specific and polarity-sensitive fluorescent probe (LD-TTP), which consists of a triphenylamine segment as an electron-donor group (D) and a pyridinium as an electron-acceptor moiety (A), forming a typical D−π−A molecular configuration. Owing to the unique intramolecular charge transfer effect, LD-TTP exhibits high sensitivity to polarity change in the linear range from Δf = 0.258 to 0.312, with over 278-fold fluorescence enhancement. Moreover, we revealed that LD-TTP possessed satisfactory ability for sensitively monitoring LDpolarity changes in living cells. Using LD-TTP, we first demonstrated the detection of LD-polarity changes in fatty liver tissues and inflammatory living mice via confocal laser scanning fluorescence imaging. Surprisingly, the visualization of LD polarity has been achieved not only at the cellular levels and living organs but also in surgical specimens from cancer patients, thus holding great potential in the clinical diagnosis of human cancer. All these features render LD-TTP an effective tool for medical diagnosis of LD polarity-related diseases.

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