Carbon dots (CDs)-based nanoparticles have been extensively explored for biological applications in sensing and bioimaging. However, the major translational barriers to CDs for imaging and sensing applications include synthetic strategies to obtain monodisperse CDs with tunable structural, electronic, and optical properties in order to achieve high-resolution deep-tissue imaging, intracellular detection, and sensing of metal ions with high sensitivity down to nanomolar levels. Herein, we report a novel strategy to synthesize and develop a multifunctional nitrogen-doped CDs probe of different sizes using a new combination of carbon and nitrogen sources. Our results show that the structural characteristics (i.e., the surface density of emissive traps and bandgaps levels) depend on the size of the CDs, which ultimately influences their optical properties. This work also demonstrates the development of a two-photon dual-emissive fluorescent multifunctional probes (3-FCDs) by conjugating fluorescein isothiocyanate on the surface of nitrogen-doped CDs. 3-FCDs show excellent near-infrared two-photon excitation ability, single-wavelength excitation, high photostability, biocompatibility, low cytotoxicity, and good cell permeability. Using two-photon fluorescence imaging, our multifunctional probe shows excellent deep-tissue high-resolution imaging capabilities with penetration depth up to 3000 and 280 μm in hydrogel scaffold and pigskin tissue, respectively. The designed probe exhibits ultrasensitivity and specificity toward Fe3+ ions with a remarkable detection limit of 2.21 nM using two-photon excitation. In addition, we also demonstrate the use of multifunctional CDs probe for ultrasensitive exogenous and real-time endogenous sensing of Fe3+ ions and imaging in live fibroblasts with rapid response times for intracellular ferric ion detection.

Recently, carbon dots (CDs) have been widely investigated for biological applications in imaging. One-step hydrothermal synthesis is considered to be one of the most promising methods for the synthesis of...

No abstract

Carbon dots have been gaining attention in the field of nanobiotechnology due to their superior photostability, high water solubility, ease of synthesis and surface functionalization, chemical inertness, low toxicity, and excellent biocompatibility. They also exhibit good two-photon absorption and unique tunable optical properties across a wide range of wavelengths, from ultraviolet to near infrared endowing them with potential for a variety of biological applications. Recently, there has been a growing interest in the synthesis and development of red-emissive two-photon carbon dots. Here we present recent progress in the design requirements for red-emissive two-photon carbon dots, and review current state-of-the-art systems, covering their applications in bioimaging, biosensing, and photothermal and photodynamic therapy.

No abstract

Nanoparticles are key vehicles for targeted therapies because they can pass through biological barriers, enter into cells, and distribute within cell structures. We investigated the synthesis of blue and green emissive hexagonal boron nitride quantum dots (hBNQDs) using a liquid-exfoliation technique followed by hydrothermal treatment. A distinct shift from blue to bright-green emission was observed upon surface passivating the dots using poly­(ethylene glycol) or PEG200 under the same UV irradiation. The quantum yield of the hBNQDs increased with the surface passivation. Multiplexed imaging was accomplished using the hBNQDs in conjunction with organic dyes. The hBNQDs provided images with distinctive emission wavelengths and fluorescence lifetimes. Although the fluorescence signals of blue- and green-emissive hBNQDs overlap spectrally with those of the emission wavelengths of the organic dyes, the fluorescence lifetime data were resolved temporally using software-based time gates. The blue-emissive hBNQD-b quantum dots were validated as sensitive platforms for detecting intracellular ferric ions with a low limit of detection (20.6 nM). The green-emissive hBNQD-g quantum dots successfully identified intracellular variations in pH, and the localization in human breast cancer cells was determined during their life cycles via fluorescence lifetime imaging.

The tissue engineering approach for repair and regeneration has achieved significant progress over the past decades. However, challenges remain in developing strategies to solve the declined or impaired innate cell and tissue regeneration capacity that occurs with aging. Cellular senescence is a key mechanism underlying organismal aging and is responsible for the declined tissue regeneration capacity in the aging population. Therefore, to promote the diminished tissue regeneration ability in the aged population, it is critical to developing a feasible and promising strategy to target senescent cells. Recent advances in nanomaterials have revolutionized biomedical applications ranging from biosensing to bioimaging and targeted drug delivery. In this perspective, we review and discuss the nature and influences of cell-intrinsic and cell-extrinsic factors on reduced regenerative abilities through aging and how nanotechnology can be a therapeutic avenue to sense, rejuvenate, and eliminate senescent cells, thereby improving the tissue regeneration capacity in the aging population.

No abstract