Conjugated Quantum Dots Inhibit the Amyloid β (1–42) Fibrillation Process

Nanoparticles have enormous potential in diagnostic and therapeutic studies. We have demonstrated that the amyloid beta mixed with and conjugated to dihydrolipoic acid- (DHLA) capped CdSe/ZnS quantum dots (QDs) of size approximately 2.5 nm can be used to reduce the fibrillation process. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used as tools for analysis of fibrillation. There is a significant change in morphology of fibrils when amyloid β (1–42) (Aβ (1–42)) is mixed or conjugated to the QDs. The length and the width of the fibrils vary under modified conditions. Thioflavin T (ThT) fluorescence supports the decrease in fibril formation in presence of DHLA-capped QDs

Nontoxic Carbon Dots Potently Inhibit Human Insulin Fibrillation

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-Dotswere able to efficiently inhibit insulin fibrillation in a concentration-dependent manner. Theinhibiting 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

Dihydrolipoic Acid Conjugated Carbon Dots Accelerate Human Insulin Fibrillation

Protein fibrillation is believed to play an important role in the pathology and development of several human diseases, such as Alzheimer’s disease, Parkinson’s disease and type 2 diabetes. Carbon dots (CDs), as a new type of nanoparticle have recently been extensively studied for potential biological applications, but their effects on protein fibrillation remain unexplored. In reality, any application in biological systems will inevitably have “contact” between proteins and CDs. In this study, human insulin was selected as a model protein to study the effects of CDs on protein fibrillation, as proteins may share a common mechanism to form fibrils. Hydrophobic CDs were conjugated with dihydrolipoic acid (DHLA-CDs) to facilitate their water solubility. Characterizations from thioflavin T fluorescence, circular dichroism spectroscopy and atomic force microscopy demonstrate that the presence of DHLA-CDs results in a higher rate of human insulin fibrillation, accelerating the conformational changes of human insulin from α-helix to β-sheet. This promoting effect is likely associated with the locally increased concentration of human insulin adsorbed on the surface of DHLA-CDs

A multiplexed immunoassay system based upon reciprocating centrifugal microfluidics

A novel, centrifugal disk-based micro-total analysis system (mu TAS) for low cost and high throughput semi-automated immunoassay processing was developed. A key innovation in the disposable immunoassay disk design is in a fluidic structure that enables very efficient micro-mixing based on a reciprocating mechanism in which centrifugal acceleration acting upon a liquid element first generates and stores pneumatic energy that is then released by a reduction of the centrifugal acceleration, resulting in a reversal of direction of flow of the liquid. Through an alternating sequence of high and low centrifugal acceleration, the system reciprocates the flow of liquid within the disk to maximize incubation/hybridization efficiency between antibodies and antigen macromolecules during the incubation/hybridization stage of the assay. The described reciprocating mechanism results in a reduction in processing time and reagent consumption by one order of magnitude.open121

Surface and supramolecular chemistry studies of selected cross-linked macromolecular systems

A principal focus of this thesis is the study of the surface chemistry of enzymatically (DHP) and photochemically (PCP) polymerized lignin model compounds, and a novel modified PEG-NC hydrogel. ESEM and SEM imaging, surface force spectroscopy, and Langmuir film studies of lignin model compounds were performed. It is found that the enzymatic lignin model compound has at least four different organizational orders of supramolecular structures. Modules of about 20 monomers are formed first in nanometer size range, and subsequently polymerize into supermodules containing about 500 monomers stretching to the tens of nanometers in size. Such supermodules subsequently aggregate into globular or spherulitic assemblies, averaging about 400 nm in diameter. Finally, the globules form clusters and large superstructures, stretching several micrometers in size. A formation of complex regular motifs, such as long chains, triangular, hexagonal and spiral-like structures, as well as regular colloidal crystal lattice assemblies of DHP lignin model compound spherulites has been observed. Organization of the enzymatic lignin model compound is strongly influenced by substrate surface properties, with most ordered structures achieved on cellulose film substrates and the least ordered on the graphite. On the other hand, the photochemical lignin model compound expresses less ordered structure incapable of forming any of the complex regular motifs. Evidence of the existence of a strong intermolecular force between two enzymatically polymerized lignin model compound macromolecules is revealed by AFM force spectroscopy, and this force is considered responsible for arranging lignin globules together in higher ordered structures. Based on combined AFM, Langmuir film and ESEM observations, a hypothesis is provided that the DHP lignin model compound globule is not just a simple block-copolymer micelle, but that it consists of at least two individual spherical layers, with space in between filled with solvent or gas.Using the ESEM for topographical and AFM for rheological study, a structural change of a surface of a novel PEG-NC potentially biocompatible hydrogel has been probed as a function of reversible photocross-linking/photocleavage. A reversible significant change in both gel surface topography and in the modulus of elasticity of the hydrogel as a function of the reversible photo-crosslinking (at 365 nm) and photocleavage (at 254 nm) has been observed. The initial photo-crosslinked hydrogel possesses a modulus of elasticity in about E = 600,000 Pa, while the modulus of elasticity of the photocleaved hydrogel is approximately E = 3,000 Pa which is about the same as the modulus of elasticity of a mammalian cells. Such properties indicate possible applicability of this novel material as a potential biomaterial for cartilage tissue replacement and other similar biomedical application were morphing of the material and its solidifying/annealing need to be done in-situ

Demonstrating a Thermodynamics Fountain: Heating Up the Classroom with an Energy Transfer Exercise

Presents a materials list and recommended procedures for demonstrating a thermal fountain. Discusses the chemistry involved in the reaction. (DDR

Surface chemistry of Alzheimer's disease: A Langmuir monolayer approach

Amyloid beta (1–40) and (1–42) peptides are the major constituents of hallmark senile plaques found in Alzheimer's disease (AD) patients. Study of aggregation of Aβ (1–40) and (1–42) peptides and the truncated Aβ fragments could lead towards the mechanism of AD. Langmuir monolayer approach is one of the excellent methods to investigate the mechanism and origin of AD. Particularly, to study the steps involved in the formation and assembly of β-sheet structures leading to formation of amyloid fibrils. Surface pressure– and surface potential–area isotherms provide information regarding the nature of short-range and long-range interactions between the molecules especially the lipids and the Aβ peptides. Spectroscopic methods like IRRAS, PM-IRRAS, FTIR-ATR, and GIXD at the air–water interface provide insight into the structural characterization, and orientation of the molecules in the Langmuir monolayer