/pdf/self-assembled-monolayers-of-thiolates-on-metals-as-a-form-1neb0hj3k4.pdf

Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

Rapid growth in nanotechnology is increasing the likelihood of engineered nanomaterials coming into contact with humans and the environment. Nanoparticles interacting with proteins, membranes, cells, DNA and organelles establish a series of nanoparticle/biological interfaces that depend on colloidal forces as well as dynamic biophysicochemical interactions. These interactions lead to the formation of protein coronas, particle wrapping, intracellular uptake and biocatalytic processes that could have biocompatible or bioadverse outcomes. For their part, the biomolecules may induce phase transformations, free energy releases, restructuring and dissolution at the nanomaterial surface. Probing these various interfaces allows the development of predictive relationships between structure and activity that are determined by nanomaterial properties such as size, shape, surface chemistry, roughness and surface coatings. This knowledge is important from the perspective of safe use of nanomaterials.

Understanding biophysicochemical interactions at the nano–bio interface

One of the fastest moving and most exciting interfaces of nanotechnology is the use of quantum dots (QDs) in biology. The unique optical properties of QDs make them appealing as in vivo and in vitro fluorophores in a variety of biological investigations, in which traditional fluorescent labels based on organic molecules fall short of providing long-term stability and simultaneous detection of multiple signals. The ability to make QDs water soluble and target them to specific biomolecules has led to promising applications in cellular labelling, deep-tissue imaging, assay labelling and as efficient fluorescence resonance energy transfer donors. Despite recent progress, much work still needs to be done to achieve reproducible and robust surface functionalization and develop flexible bioconjugation techniques. In this review, we look at current methods for preparing QD bioconjugates as well as presenting an overview of applications. The potential of QDs in biology has just begun to be realized and new avenues will arise as our ability to manipulate these materials improves.

Quantum dot bioconjugates for imaging, labelling and sensing

We investigated the intracellular uptake of different sized and shaped colloidal gold nanoparticles. We showed that kinetics and saturation concentrations are highly dependent upon the physical dimensions of the nanoparticles (e.g., uptake half-life of 14, 50, and 74 nm nanoparticles is 2.10, 1.90, and 2.24 h, respectively). The findings from this study will have implications in the chemical design of nanostructures for biomedical applications (e.g., tuning intracellular delivery rates and amounts by nanoscale dimensions and engineering complex, multifunctional nanostructures for imaging and therapeutics).

Determining the size and shape dependence of gold nanoparticle uptake into mammalian cells.

This review is written with the goal of informing public health concerns related to nanoscience, while raising awareness of nanomaterials toxicity among scientists and manufacturers handling them. We show that humans have always been exposed to nanoparticles and dust from natural sources and human activities, the recent development of industry and combustion-based engine transportation profoundly increasing anthropogenic nanoparticulate pollution. The key to understanding the toxicity of nanoparticles is that their minute size, smaller than cells and cellular organelles, allows them to penetrate these basic biological structures, disrupting their normal function. Among diseases associated with nanoparticles are asthma, bronchitis, lung cancer, neurodegenerative diseases (such as Parkinson`s and Alzheimer`s diseases), Crohn`s disease, colon cancer. Nanoparticles that enter the circulatory system are related to occurrence of arteriosclerosis, and blood clots, arrhythmia, heart diseases, and ultimately cardiac death. We show that possible adverse effects of nanoparticles on human health depend on individual factors such as genetics and existing disease, as well as exposure, and nanoparticle chemistry, size, shape, and agglomeration state. The faster we will understand their causes and mechanisms, the more likely we are to find cures for diseases associated with nanoparticle exposure. We foresee a future with better-informed, and hopefully more cautious manipulation of engineered nanomaterials, as well as the development of laws and policies for safely managing all aspects of nanomaterial manufacturing, industrial and commercial use, and recycling.

Nanomaterials and nanoparticles: Sources and toxicity

Toxicity of Gold Nanoparticles Functionalized with Cationic and Anionic Side Chains

Thioalkyl and thioalkylated oligo(ethylene glycol) (OEG) ligands with chain-end functionality were used to fabricate water-soluble CdSe nanoparticle scaffolds. Surface recognition of chymotrypsin (ChT) was achieved using these functionalized nanoparticle scaffolds, with three levels of interaction demonstrated: no interaction (OEG terminated with hydroxyl group), inhibition with denaturation (carboxylate-terminated thioalkyl ligands), and inhibition with retention of structure (carboxylate-terminated OEG). The latter process was reversible upon an increase in ionic strength, with essentially complete restoration of enzymatic activity.

Control of Protein Structure and Function through Surface Recognition by Tailored Nanoparticle Scaffolds

Anionically functionalized amphiphilic nanoparticles efficiently inhibit chymotrypsin through electrostatic binding followed by protein denaturation. We demonstrate the ability to disrupt this "irreversible" inhibition of chymotrypsin through modification of the nanoparticle surface using cationic surfactants. Up to 50% of original chymotrypsin activity is rescued upon long-chain surfactant addition. Dynamic light-scattering studies demonstrate that chymotrypsin is released from the nanoparticle surface. The conformation of the rescued chymotrypsin was characterized by fluorescence and fluorescence anisotropy, indicating that chymotrypsin regains a high degree of native structure upon surfactant addition.

Reversible “Irreversible” Inhibition of Chymotrypsin Using Nanoparticle Receptors

A family of nanoparticles featuring surfaces of varying hydrophobicity was synthesized. The efficiency of DNA-binding was determined, demonstrating in a fivefold modulation in binding a 37-mer DNA strand. Nanoparticle-binding causes a reversible conformational change in the DNA structure, as demonstrated by circular dichroism and fluorescence experiments. Furthermore, the affinity of the nanoparticle for the DNA can be regulated by external agents, though stability of the complex is observed at relatively high ionic strengths.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1747-0285.2006.00372.x

Catherine M. Goodman

Papers

Toxicity of Gold Nanoparticles Functionalized with Cationic and Anionic Side Chains

Control of Protein Structure and Function through Surface Recognition by Tailored Nanoparticle Scaffolds

Reversible “Irreversible” Inhibition of Chymotrypsin Using Nanoparticle Receptors

DNA‐binding by Functionalized Gold Nanoparticles: Mechanism and Structural Requirements

A Peptide Flavoprotein Mimic: Flavin Recognition and Redox Potential Modulation in Water by a Designed β Hairpin