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

Surface Engineering Quantum Dots at the Air-Water Interface

Quantum dots (QD) have been modified with surfactants of varying chain lengths. These QD-surfactants can form a stable monolayer at the air-water interface. A possible explanation for the different behaviors of modified QDs may be found in the roles of trioctylphosphine oxide on the QD surface. It has been shown that QD are submicron-sized structures that are able to confine excitons in one or more directions. Electron confinement in all three dimensions is called “quantum confinement,” and the particles QD with a main characteristic of discrete levels of energy not continuous such as in metals. Langmuir films are formed by spreading an amphiphilic molecule at the air-water interface and its interface properties are studied upon compression of the film. The main requirement of the molecule is that the solvent in which it is dissolved should be immiscible with water and fairly volatile

ZL-DHP lignin model compound at the air-water interface

In this paper we present our surface chemistry studies of enzymatically polymerized, poly-coniferyl alcohol lignin model compound (dehydrogenate polymer a.k.a. ZL-DHP) at the air-water interface. Using the CHCl3/MeOH (5:1 v/v) spreading solvent, we found an average molecular area of ZL-DHP of approximately 1200 Angstrom(2). The monolayer expresses a high compressibility with a collapsed area of 500 Angstrom(2) and collapsed surface pressure of 28 mN m(-1). In the range of applied surface pressures, ZL-DHP polymer have no phase changes, as shown by the very high linearity (R=0.994) of absorbance vs. surface pressure cure. There was no symmetry transitions observed as shown by absence of shifts of absorption peak maximums

Detection of organophosphorus compounds by covalently immobilized organophosphorus hydrolase

As a consequence of organophosphorus (OP) toxins posing a threat to human life globally, organophosphorus hydrolase (OPH) has become the enzyme of choice to detoxify such compounds. Organophosphorus hydrolase was covalently immobilized onto a quartz substrate for utilization in paraoxon detection. The substrate was cleaned and modified prior to chemical attachment. Each modification step was monitored by imaging ellipsometry as the thickness increased with each modification step. The chemically attached OPH was labeled with a fluorescent dye (7-isothiocyanato-4-methylcoumarin) for the detection of paraoxon in aqueous solution, ranging from 10(-9) to 10(-5) M. UV-visible spectra were also acquired for the determination of the hydrolysis product of para-oxon, namely p-nitrophenol

Immobilization of Quantum Dots in the Photo-Cross-Linked Poly(ethylene glycol)-Based Hydrogel

An inorganic/organic composite hybrid nano-system has been successfully synthesized in which nanocrystalline quantum dots (QDs) were effectively immobilized within a photo-cross-linked poly(ethylene glycol) (PEG) hydrogel. The immobilization of 3.5−6.0 nm CdTe and 2.0−3.5 nm CdSe QDs within the PEG hydrogel network has been shown to be effective through utilization of physical trapping. These QD-immobilized gel systems demonstrated luminescence characteristics unique to semiconductor QD nanocrystals. Controlled particle extraction from the PEG hydrogel matrix may be possible via a photocleavage process. The solubility property of QDs was controlled through surface functionalization. It is envisioned that the unique photophysical properties of this new material can be utilized as a convenient signal transducer for chemo-/bio-sensing. A promising application of the described QD/PEG-NC hybrid system may be in the fields of fluoroimmunoassay and as a monitoring system for drug delivery and wound healing