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One prevention and therapeutic strategy for diseases associated with peptide or protein fibrillation is to inhibit or delay the fibrillation process. Carbon dots (C–Dots) have recently emerged as benign nanoparticles to replace toxic quantum dots and have attracted great attention because of their unique optical properties and potential applications in biological systems. However, the effect of C-Dots on peptide or protein fibrillation has not been explored. In this in vitro study, human insulin was selected as a model to investigate the effect of C-Dots on insulin fibrillation. Water-soluble fluorescent C-Dots with sizes less than 6 nm were prepared from carbon powder and characterized by UV–vis spectroscopy, fluorescence, Fourier transform infrared spectrophotometry, X-ray photoelectron spectrometry, transmission electron microscopy, and atomic force microscopy. These C-Dots were able to efficiently inhibit insulin fibrillation in a concentration-dependent manner. The inhibiting effect of C-Dots was even observed at 0.2 μg/mL. Importantly, 40 μg/mL of C-Dots prevent 0.2 mg/mL of human insulin from fibrillation for 5 days under 65 °C, whereas insulin denatures in 3 h under the same conditions without C-Dots. The inhibiting effect is likely due to the interaction between C-Dots and insulin species before elongation. Cytotoxicity study shows that these C-Dots have very low cytotoxicity. Therefore, these C-Dots have the potential to inhibit insulin fibrillation in biological systems and in the pharmaceutical industry for the processing and formulation of insulin.

Understanding the interaction between graphene oxide (GO) and the biomolecules is fundamentally essential, especially for disease- and drug-related peptides and proteins. In this study, GO was found to strongly interact with amino acids (tryptophan and tyrosine), peptides (Alzheimer's disease related amyloid beta 1-40 and type 2 diabetes related human islet amyloid polypeptide), and proteins (drug-related bovine and human serum albumin) by fluorescence quenching, indicating GO was a universal quencher for tryptophan or tyrosine related peptides and proteins. The quenching mechanism between GO and tryptophan (Trp) or tyrosine (Tyr) was determined as mainly static quenching, combined with dynamic quenching (Förster resonance energy transfer). Different quenching efficiency between GO and Trp or Tyr at different pHs indicated the importance of electrostatic interaction during quenching. Hydrophobic interaction also participated in quenching, which was proved by the presence of nonionic amphiphilic copolymer Pluronic F127 (PF127) in GO dispersion. The strong hydrophobic interaction between GO and PF127 efficiently blocked the hydrophobic interaction between GO and Trp or Tyr, lowering the quenching efficiency.

Among various cancers, pediatric brain tumors represent the most common cancer type in children and the second most common cause of cancer related deaths. Anticancer drugs and therapies, such as doxorubicin (Dox), have severe side effects on patients during chemotherapy, especially for children as their bodies are still under development. These side effects are believed to be due to the lack of a delivery system with high efficacy and targeting selectivity, resulting in serious damages of normal cells. To improve the efficacy and selectivity, the transferrin (Trans) receptor mediated endocytosis can be utilized for drug delivery system design, as transferrin receptors are expressed on the blood brain barrier (BBB) and often over expressed in brain tumor cells. Carbon dots (C-Dots) have recently emerged as benign nanoparticles in biomedical applications owing to their good water solubility, tunable surface functionalities and excellent biocompatibility. The unique characteristics of C-Dots make them promising candidates for drug delivery development. In this study, carbon dots-transferrin-doxorubicin covalent conjugate (C-Dots-Trans-Dox) was synthesized, characterized by different spectroscopic techniques and investigated for the potential application as a drug delivery system for anticancer drug doxorubicin to treat pediatric brain tumors. Our in vitro results demonstrate greater uptake of the C-Dots-Trans-Dox conjugate compared to Dox alone presumably owing to the high levels of transferrin receptors on these tumor cells. Experiment showed that C-Dots-Trans-Dox at 10 nM was significantly more cytotoxic than Dox alone, reducing viability by 14-45%, across multiple pediatric brain tumor cell lines.

Bone tissue engineering (BTE) has received significant attention due to its enormous potential in treating critical‐sized bone defects and related diseases. Traditional materials such as metals, ceramics, and polymers have been widely applied as BTE scaffolds; however, their clinical applications have been rather limited due to various considerations. Recently, carbon‐based nanomaterials attract significant interests for their applications as BTE scaffolds due to their superior properties, including excellent mechanical strength, large surface area, tunable surface functionalities, high biocompatibility as well as abundant and inexpensive nature. In this article, recent studies and advancements on the use of carbon‐based nanomaterials with different dimensions such as graphene and its derivatives, carbon nanotubes, and carbon dots, for BTE are reviewed. Current challenges of carbon‐based nanomaterials for BTE and future trends in BTE scaffolds development are also highlighted and discussed.

Cardiovascular disease (CVD) has threatened human lives for decades, and a technique for estimating and healing is still needed. There has been increasing interest in finding CVD diagnostic biomarkers to predict risk. Cardiac troponin I (cTnI) has proven to be a significant biomarker for acute myocardial infarction detection. An immunoassay based biosensor for cTnI can play an important role in diagnosis of CVD. Over the past decades, various methodologies regarding cTnI detection have been studied, including colorimetric, fluorescence, paramagnetic, electrochemical, and surface plasmon resonance. This review will focus more on recent strategies about surface immobilized cTnI detection.

Bone-related diseases and dysfunctions are heavy burdens on our increasingly aged society. One important strategy to relieve this problem is through early detection and treatment of bone-related diseases. Towards this goal, there has been constant interest in developing novel bone-specific materials for imaging and drug delivery. Currently, however, materials that have high affinity and specificity towards bone are very limited. Carbon dots (C-dots) synthesized from carbon nanopowder bind to calcified bones in vivo with high affinity and specificity. In this study we show that bone binding is highly unique to a specific type of C-dots, and that this binding is non-toxic. Significantly, C-dots derived from other raw materials did not show any bone binding properties. These differences are attributed to differences in surface chemistry of C-dots preparations, highlighting the heterogeneous nature of C-dots. Importantly, bone-binding by carbon nanopowder derived C-dots are not significantly altered by chemical functionalization of their surface. These unique properties indicate the potential applications of carbon nanopowder-derived C-dots as highly bone-specific bioimaging agents and drug carriers.

Drug delivery to the central nervous system (CNS) in biological systems remains a major medical challenge due to the tight junctions between endothelial cells known as the blood-brain-barrier (BBB). Here we use a zebrafish model to explore the possibility of using transferrin-conjugated carbon dots (C-Dots) to ferry compounds across the BBB. C-Dots have previously been reported to inhibit protein fibrillation, and they are also used to deliver drugs for disease treatment. In terms of the potential medical application of C-Dots for the treatment of CNS diseases, one of the most formidable challenges is how to deliver them inside the CNS. To achieve this in this study, human transferrin was covalently conjugated to C-Dots. The conjugates were then injected into the vasculature of zebrafish to examine the possibility of crossing the BBB in vivo via transferrin receptor-mediated endocytosis. The experimental observations suggest that the transferrin-C-Dots can enter the CNS while C-Dots alone cannot.