Tyrosine carbon dots inhibit fibrillation and toxicity of the human islet amyloid polypeptide

Red emissive fluorescent carbon dots based on ternary carbon source for imaging α-synuclein fibrils

The misfolding and aggregation of α-synuclein monomers usually cause the occurrence and development of Parkinson's disease (PD). It is important to develop effective methods for detection of α-synuclein aggregates. Carbon dots (CDs) could be the potential fluorescence probe for this purpose owing to their appreciated optical properties. However, undefined structure of CDs and complicated three-dimensional structure of protein severely hindered the design of fluorescence probe towards protein aggregates. Herein, a red emissive fluorescent amphiphilic CD, named as CL-9, was designed with a high sensitivity to α-synuclein fibrils by a one-step heating process, using the ternary carbon source, including Congo red, l-tryptophan and urea. The CL-9 exhibited turn-on red emissive fluorescence towards α-synuclein fibril, but remained no change towards its monomer. Compared with the original Congo red dye, CL-9 exhibited stronger turn-on red fluorescence towards α-synuclein fibrils with better anti-photobleaching resistance, biocompatibility and signal-to-noise ratio. The CL-9 was successful as a fluorescent probe to image α-synuclein fibrils in NL-5901 C. elegans. The present study provided a feasible approach using the multiple carbon sources to construct the CDs based fluorescence probe targeting amyloid proteins.

Nitrogen-doped carbon dots derived from ellagic acid and L-tyrosine for photothermal anticancer and anti-inflammation

Photothermal therapy (PTT) of tumor would ineluctably cause oxidative stress and related inflammation in adjacent normal tissues, leading to a discounted therapeutic outcome. To address this issue, herein an innovative therapeutic strategy that integrates photothermal anticancer and normal cell protection is developed. A new type of nitrogen-doped carbon dot (ET-CD) has been synthesized in one step by hydrothermal method using ellagic acid and L-tyrosine as reaction precursors. The as-prepared ET-CD exhibits high photothermal conversion efficiency and good photothermal stability. After intravenous injection, ET-CD can accumulate at the tumor site and the hyperthermia generated under near infrared laser irradiation effectively ablates tumor tissues, thereby significantly inhibiting tumor growth. Importantly, owing to the inherited antioxidant activity from ellagic acid, ET-CD can remove reactive oxygen and nitrogen species produced in the body and reduce the levels of inflammatory factors induced by oxidative stress, so as to alleviate the damage caused by heat-induced inflammation to normal cells and tissues while photothermal anticancer. These attractive features of ET-CD may open the exploration of innovative therapeutic strategies to promote the clinical application of PTT.

Dissimilar effects of the hydrophilic carbon dots on the amyloid aggregation of two model proteins and the mechanism discussion

Many proteins could aggregate into amyloid fibrils under certain conditions. However, the aggregation process and morphology of the fibrils may be significantly different because of the distinct protein structure. In this article, the hydrophilic carbon dots (Lys-CA-CDs) were prepared using lysine (Lys) and citric acid (CA) as reactant under the assistance of a microwave. The dissimilar modulation effect of Lys-CA-CDs on the aggregation process of distinct structure protein was further investigated, where bovine serum albumin (BSA) and hen egg white lysozyme (HEWL) were chosen as model proteins. All results showed that Lys-CA-CDs displayed the contrary influence on the aggregation process of BSA and HEWL. Lys-CA-CDs could induce BSA to aggregate into more wormlike fibrils and inhibit the aggregation of HEWL into hair-like fibrils. The influence on the aggregation process of BSA may be assigned to the increased concentration of BSA around the Lys-CA-CDs caused by their interaction. However, inserting of Lys-CA-CDs into the inner structure of HEWL led to the change of protein secondary structure. The change of secondary structure further made it difficult for HEWL to aggregate into fibrils and Lys-CA-CDs showed the inhibition effect on HEWL aggregation.

Carbon Dots Modified Multi Dopants Nitrogen and Boron for an Early Detection of Lead in the Environment

The remarkable optical properties and strong biocompatibility of carbon dots make them highly promising for applications in biochemical sensing and environmental testing. These carbon dots possess a surface that is easily modifiable. In this study, carbon dots have been successfully synthesized and modified by the addition of N and B dopants using the microwave method, along with the functionalization of their surface functional groups with bovine serum albumin (BSA). The maximum fluorescence intensity of N, B-CDs is observed at 462 nm when excited at a wavelength of 352 nm. N, B-CDs have a spherical size with a diameter ranging from 2 to 6 nm, confirmed by UV-Vis absorption spectra and the presence of functional groups in the FT-IR absorption patterns. BSA-functionalized N, B-CDs as the fluorescent probe demonstrate great potential as a sensor for Pb(II) ions in water, with a very low detection limit of 1.05 µg/L. This research could contribute to the development of fluorescence nanosensors.

Modulating the optical properties of carbon dots by peptide condensates

Here, we utilized designed condensates formed by liquid-liquid phase separation (LLPS) of cationic and aromatic peptide to sequester tyrosine-based carbon dots (C-dots). The C-dots fluorescence is quenched and retrieved upon partitioning and release from condensates, allowing a spatial regulation of C-dots fluorescence which can be utilized for biosensing applications.

Scavenging neurotoxic aldehydes using lysine carbon dots

Reactive aldehydes generated in cells and tissues are associated with adverse physiological effects. Dihydroxyphenylacetaldehyde (DOPAL), the biogenic aldehyde enzymatically produced from dopamine, is cytotoxic, generates reactive oxygen species, and triggers aggregation of proteins such as α-synuclein implicated in Parkinson's disease. Here, we demonstrate that carbon dots (C-dots) prepared from lysine as the carbonaceous precursor bind DOPAL molecules through interactions between the aldehyde units and amine residues on the C-dot surface. A set of biophysical and in vitro experiments attests to attenuation of the adverse biological activity of DOPAL. In particular, we show that the lysine-C-dots inhibit DOPAL-induced α-synuclein oligomerization and cytotoxicity. This work underlines the potential of lysine-C-dots as an effective therapeutic vehicle for aldehyde scavenging.

Nanoparticles and Nanocolloidal Carbon: Will They Be the Next Antidiabetic Class That Targets Fibrillation and Aggregation of Human Islet Amyloid Polypeptide in Type 2 Diabetes?

Nanotechnology is revolutionizing human medicine. Nanoparticles (NPs) are currently used for treating various cancers, for developing vaccines, and for imaging, and other promises offered by NPs might come true soon. Due to the interplay between NPs and proteins, there is more and more evidence supporting the role of NPs for treating amyloid-based diseases. NPs can induce some conformational changes of the adsorbed protein molecules via various molecular interactions, leading to inhibition of aggregation and fibrillation of several and different amyloid proteins. Though an in depth understanding of such interactions between NPs and amyloid structures is still lacking, the inhibition of protein aggregation by NPs represents a new generation of innovative and effective medicines to combat metabolic diseases such as type 2 diabetes (T2D). Here, we lay out advances made in the field of T2D notably for optimizing protein aggregation inhibition strategies. This Account covers discussions about the current understanding of β-cells, the insulin producing cells within the pancreas, under diabetic conditions, notably increased glucose and fatty acid levels, and the implication of these conditions on the formation of human islet amyloid polypeptide (hIAPP) amylin oligomers and aggregates. Owing to the great potential of carbon nanostructures to interfere with protein aggregation, an important part of this Account will be devoted to the state of the art of therapeutic options in the form of emerging nanomaterials-based amyloidosis inhibitors. Our group has recently made some substantial progress in this regard by investigating the impact of glucose and fatty acid concentrations on hIAPP aggregation and β-cell toxicity. Furthermore, the great potential of carbon nanocolloids in reversing hIAPP aggregation under diabetic conditions will be highlighted as the approach has been validated on β-cell cultures from rats. We hope that this Account will evoke new ideas and concepts in this regard. We give some lead references below on pancreatic β-cell aspects and carbon quantum dots for managing diabetics and nanomedicine related aspects, a topic of interest in our laboratory.

Inhibitory effects of carbon quantum dots towards hen egg white lysozyme amyloidogenesis through formation of a stable protein complex

Proteins, under certain circumstances such as defective quality control mechanism, mutations and altered environmental conditions, undergo misfolding and assemble into highly ordered beta-sheet structured fibrillar aggregates called amyloid fibrils. Formation of amyloid is seen in most of the protein linked degenerative diseases like Alzheimer's disease, Parkinson's disease, Huntington's disease, Type II diabetes mellitus and many more. Amyloid fibril forms via intermediate state(s), and is known to follow a nucleated condensation polymerization mechanism. Though extensive research is being carried out towards finding a therapeutic solution to the amyloidosis, an effective treatment to these diseases still remains elusive and also the mechanism of amyloidogenesis largely remains unclear. In recent times, carbon quantum dots (CQDs) are gaining the attention of researchers due to their semi-conductive nature, excellent physio-chemical properties, high surface to volume ratio, optical properties and mainly bio-compatibility. In the current study, we have synthesized CQDs from commonly available kitchen spice mix and explored their role in amyloidogenesis using hen egg white lysozyme (HEWL) as a model protein. The results clearly demonstrate the amyloid inhibitory as well as disaggregation potential of CQD by forming a stable complex with HEWL and thereby increasing the energy barrier for the aggregation process.

Antiviral Activity of Peptide-Based Assemblies

The COVID-19 pandemic highlighted the importance of developing surfaces and coatings with antiviral activity. Here, we present, for the first time, peptide-based assemblies that can kill viruses. The minimal inhibitory concentration (MIC) of the assemblies is in the range tens of micrograms per milliliter. This value is 2 orders of magnitude smaller than the MIC of metal nanoparticles. When applied on a surface, by drop casting, the peptide spherical assemblies adhere to the surface and form an antiviral coating against both RNA- and DNA-based viruses including coronavirus. Our results show that the coating reduced the number of T4 bacteriophages (DNA-based virus) by 3 log, compared with an untreated surface and 6 log, when compared with a stock solution. Importantly, we showed that this coating completely inactivated canine coronavirus (RNA-based virus). This peptide-based coating can be useful wherever sterile surfaces are needed to reduce the risk of viral transmission.