Quantum dots and prion proteins: is this a new challenge for neurodegenerative diseases imaging?

CdTe quantum dots trigger oxidative stress and endoplasmic reticulum stress-induced apoptosis and autophagy in rat Schwann cell line RSC96

In the current study, the cytotoxicity and mechanisms of cadmium telluride quantum dots (CdTe QDs) on RSC96 cells were evaluated by exposing different doses of CdTe QDs for 24 h. Two types of cell death, including apoptosis and autophagy, as well as two important organelles, mitochondria and endoplasmic reticulum, were focused after CdTe QDs exposure. The results showed that CdTe QDs induced apoptosis in RSC96 cells in a concentration-dependent manner; promoted the accumulation of intracellular reactive oxygen species; decreased the mitochondrial membrane potential; caused the release of cytochrome c; and also increased the expression of Bcl-2 associated X protein, caspase-3, and cytochrome c proteins and decreased the expression of Bcl-2 protein. Further results also confirmed that CdTe QDs could be internalized by RSC96 cells, and the exposure and internalization of CdTe QDs could induce excessive endoplasmic reticulum stress in the cells, and the expression levels of binding immunoglobulin protein, C/EBP homologous protein, and caspase12 proteins were increased in a concentration-dependent manner. Moreover, autophagy-related proteins LC3II, Beclin1, and P62 all increased after CdTe QDs exposure, suggesting that CdTe QDs exposure both promoted autophagosome formation and inhibited autophagosome degradation, and that CdTe QDs affected the autophagic flow in RSC96 cells. In conclusion, CdTe QDs are able to cause apoptosis and autophagy in RSC96 cells through mitochondrial and endoplasmic reticulum stress pathways, and the possible neurotoxicity of CdTe QDs should be further investigated.

Dual aptamer assay for detection of Acinetobacter baumannii on an electromagnetically-driven microfluidic platform

Rapid detection of Acinetobacter baumannii (AB) is critical for limiting healthcare-associated infections and providing the best treatment for infected individuals. Herein an integrated microfluidic device for AB diagnosis utilizing a new dual aptamer assay was developed for point-of-care (POC) applications; magnetic beads coated with AB-specific aptamers were used to capture bacteria, and quantum dots (QD) bound to a second aptamer were utilized to quantify the amount of bacteria with a light-emitting diode (LED)-induced fluorescence module integrated into the device. Within a rapid detection of 30 min, a limit of detection of only 100 colony-forming units (CFU)/reaction was obtained, and all necessary microfluidic devices were actuated by a combination of permanent magnets and electromagnets. The pumping rate of the micropump was 270 μL/min at only 10 V, which is amenable for POC applications with lower power consumption, and only 10 μL of sample and reagents were required. Given these attributes, an automatic POC device was demonstrated which could perform a dual aptamer assay to diagnose AB by using electromagnetically-driven microfluidic system. This system provides a rapid, sensitive, low power and reagents consumption and fully automated for AB detection by using a dual aptamer assay. It will allow rapid clinical diagnosis of AB in the near future.

Short-term assessment of cadmium toxicity and uptake from different types of Cd-based Quantum Dots in the model plant Allium cepa L

We report on the toxicity and bioaccumulation of three different types of Cd-based quantum dots (QDs), dispersed in aqueous medium, for a model plant Allium cepa L. It is believed that encapsulation of nanoparticles should reduce their toxicity and increase their stability in different environments; in this work we studied how QD encapsulation affects their phytotoxicity. Core, core/shell, and core/shell/shell QDs (CdTe, CdTe/ZnS, and CdTe/CdS/ZnS QDs capped by 2-mercaptopropionic acid) were tested and CdCl₂ was used as a positive control. After 24-h and 72-h exposure, total Cd content (M_Cd) and bioaccumulation factors (BAFs) were determined in all parts of A. cepa plants (roots, bulb, shoot), and the total length of the root system was monitored as a toxicity end-point. Measurements of total Cd content versus free Cd²⁺ content (with Differential Pulse Voltammetry, DPV) in exposure media showed differences in chemical stability of the three QD types. Correspondingly, selected QDs showed different toxicity for A. cepa and different Cd bioaccumulation patterns. CdTe QDs were the most toxic; their effect was similar to CdCl₂ due to the release of free Cd²⁺, which was confirmed by the DPV measurements. Plants exposed to CdTe QDs also bioaccumulated the most Cd among all QD exposure groups. CdTe/ZnS QDs showed no toxicity and very low bioaccumulation of Cd in A. cepa; the main source of measured Cd in the plants were QDs adsorbed on their roots, which was confirmed by fluorescence microscopy. On the contrary, CdTe/CdS/ZnS QD toxicity and bioaccumulation patterns were similar to those of CdTe QDs and pointed to unstable CdS/ZnS shells.

Implications of peptide assemblies in amyloid diseases

Neurodegenerative disorders and type 2 diabetes are global epidemics compromising the quality of life of millions worldwide, with profound social and economic implications. Despite the significant differences in pathology - much of which are poorly understood - these diseases are commonly characterized by the presence of cross-β amyloid fibrils as well as the loss of neuronal or pancreatic β-cells. In this review, we document research progress on the molecular and mesoscopic self-assembly of amyloid-beta, alpha synuclein, human islet amyloid polypeptide and prions, the peptides and proteins associated with Alzheimer's, Parkinson's, type 2 diabetes and prion diseases. In addition, we discuss the toxicities of these amyloid proteins based on their self-assembly as well as their interactions with membranes, metal ions, small molecules and engineered nanoparticles. Through this presentation we show the remarkable similarities and differences in the structural transitions of the amyloid proteins through primary and secondary nucleation, the common evolution from disordered monomers to alpha-helices and then to β-sheets when the proteins encounter the cell membrane, and, the consensus (with a few exceptions) that off-pathway oligomers, rather than amyloid fibrils, are the toxic species regardless of the pathogenic protein sequence or physicochemical properties. In addition, we highlight the crucial role of molecular self-assembly in eliciting the biological and pathological consequences of the amyloid proteins within the context of their cellular environments and their spreading between cells and organs. Exploiting such structure-function-toxicity relationship may prove pivotal for the detection and mitigation of amyloid diseases.

Antimicrobial Nanostructures for Neurodegenerative Infections

Nanostructures have been widely involved in changes in the drug delivery system. Nanoparticles have unique physicochemical properties, e.g., ultrasmall size, large surface area, and the ability to target specific actions. Various nanomaterials, like Ag, ZnO, Cu/CuO, and Al₂O₃, have antimicrobial activity. Basically, six mechanisms are involved in the production of antimicrobial activity, i.e., (1) destruction of the peptidoglycan layer, (2) release of toxic metal ions, (3) alteration of cellular pH via proton efflux pumps, (4) generation of reactive oxygen species, (5) damage of nuclear materials, and (6) loss of ATP production. Nanomedicine contributes to various pharmaceutical applications, like diagnosis and treatment of various ailments including microbial diseases. Furthermore, nanostructured antimicrobial agents are also involved in the treatment of the neuroinfections associated with neurodegenerative disorders. This chapter focuses on the nanostructure and nanomedicine of antimicrobial agents and their prospects for the possible management of infections associated with neurodegenerative disorders.