Drug delivery across the blood–brain barrier (BBB) is one of the biggest challenges in modern medicine due to the BBB’s highly semipermeable property that limits most therapeutic agents of brain diseases to enter the central nervous system (CNS). In recent years, nanoparticles, especially carbon dots (CDs), exhibit many unprecedented applications for drug delivery. Several types of CDs and CD-ligand conjugates have been reported successfully penetrating the BBB, which shows a promising progress in the application of CD-based drug delivery system (DDS) for the treatment of CNS diseases. In this review, our discussion of CDs includes their classification, preparations, structures, properties, and applications for the treatment of neurodegenerative diseases, especially Alzheimer’s disease (AD) and brain tumor. Moreover, abundant functional groups on the surface, especially amine and carboxyl groups, allow CDs to conjugate with diverse drugs as versatile drug nanocarriers. In addition, structure of the BBB is briefly described, and mechanisms for transporting various molecules across the BBB and other biological barriers are elucidated. Most importantly, recent developments in drug delivery with CDs as BBB-penetrating nanodrugs and drug nanocarriers to target CNS diseases especially Alzheimer’s disease and brain tumor are summarized. Eventually, future prospects of the CD-based DDS are discussed in combination with the development of artificial intelligence and nanorobots.

The advantages of near infrared (NIR)-to-visible upconversion nanoparticles (UCNP) for latent fingerprint development have been previously documented. In the present study, the use of NIR-to-NIR UCNP, composed of β-NaYF4:2%Tm, 48%Yb, is evaluated for latent fingerprint analysis. Here, 976 nm illumination is used to generate 800 nm luminescent fingerprint images. NIR-to-NIR UCNP are demonstrated to have significant advantages over NIR-to-visible UCNP in developing latent fingerprints. NIR-to-NIR UCNP are significantly brighter than NIR-to-green β-NaYF4:2%Er, 18%Yb UCNP of comparable size, so that lower irradiance is required to obtain high-quality images. The increased brightness is due mainly to the much higher internal quantum yield of the NIR-to-NIR UCNP at the irradiance levels used for imaging. Imaging at 800 nm often significantly reduces the background interference from substrates with complex printed patterns because many inks do not absorb appreciably at 800 nm. In most instances, imaging can be performed in full room lighting without significant degradation of the image because modern lighting produces very little output in the NIR. Using β-NaYF4:2%Tm, 48%Yb@NaYF4 core–shell nanoparticles, fingerprints can be imaged easily using excitation irradiance levels below 100 mW·cm–2. The intrinsic quantum yields of the NIR-to-NIR upconversion are estimated for the nanomaterials used in this study at typical irradiance levels used here to image fingerprints. It is shown that the method for processing as-synthesized UCNP into powders has significant impact on the effective particle size in fingerprint development and on how the particles coat the fingerprint residue. The method demonstrated here produces fingerprint images of high resolution, as evidenced by the high number of minutiae which can be identified.

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Pediatric brain tumors remain a significant source of morbidity and mortality. Though developments have been made in treating these malignancies, the blood–brain barrier, intra- and inter-tumoral heterogeneity, and therapeutic toxicity pose challenges to improving outcomes. Varying types of nanoparticles, including metallic, organic, and micellar molecules of varying structures and compositions, have been investigated as a potential therapy to circumvent some of these inherent challenges. Carbon dots (CDs) have recently gained popularity as a novel nanoparticle with theranostic properties. This carbon-based modality is highly modifiable, allowing for conjugation to drugs, as well as tumor-specific ligands in an effort to more effectively target cancerous cells and reduce peripheral toxicity. CDs are being studied pre-clinically. The ClinicalTrials.gov site was queried using the search terms: brain tumor and nanoparticle, liposome, micelle, dendrimer, quantum dot, or carbon dot. At the time of this review, 36 studies were found, 6 of which included pediatric patients. Two of the six studies investigated nanoparticle drug formulations, whereas the other four studies were on varying liposomal nanoparticle formulations for the treatment of pediatric brain tumors. Here, we reviewed the context of CDs within the broader realm of nanoparticles, their development, promising pre-clinical potential, and proposed future translational utility.