Nano LIFE

Semiconductor quantum dots (QDs) have achieved initial success as biomedical imaging agents. However, significant cytotoxicity in the biological environment prohibits their use in vivo. Here, we introduce nanocomposites composed of carbon dots (C-dots) in poly(lactic-co-glycolic acid) (PLGA) carriers as possible imaging agents for in vivo applications. An initial hurdle to clinical use is overcome by synthesizing C-dots with commercially available carbon black precursors, permitting scalable nanomanufacturing. These fluorescent nanoparticles, which have a mean diameter of ~1 nm, display a disordered graphitic structure. To overcome a second clinical hurdle (i.e., rapid renal clearance of nanoparticles <~6 nm in diameter), C-dots were encapsulated in biodegradable PLGA nanospheres. The resulting nanocomposites showed a mean diameter of 344 ± 23 nm, which should reduce renal clearance. With further optimization, nanocarriers could be optimized to sizes <200 nm to reduce accumulation in the reticuloendothelial system (RES). Toxicity of both C-dots and C-dot-PLGA nanocomposites was evaluated using HepG2 liver cell lines. Unlike QDs, which can induce toxicological responses at concentrations as low as 0.005 mg/mL, C-dots exhibited cytotoxicity at concentrations greater than 0.2 mg/mL, while their derived nanocomposites did not exhibit cytotoxicity at any concentration tested (i.e., 0.02 mg/mL, 0.1 mg/mL and 0.2 mg/mL).

The interaction between platelet integrin αIIbβ3 and fibrin (ogen) plays a key role in blood clot formation and stability. Integrin antagonists, a class of pharmaceuticals used to prevent and treat cardiovascular disease, are designed to competitively interfere with this process. However, the energetics of the integrin–drug binding are not fully understood, potentially hampering further development of this class of pharmaceuticals. We integrated dynamic force spectroscopy (DFS) and surface plasmon resonance (SPR) to probe the energetics of complex formation between αIIbβ3 and cHarGD, a cyclic peptide integrin antagonist. Analysis of αIIbβ3:cHarGD DFS rupture force data at pulling rates of 14 000 pN/s, 42 000 pN/s and 70 000 pN/s yielded k_off = 0.02–0.09 s^-1, a dissociation energy barrier , and a potential well width x_-1 = 0.5–0.8 nm. SPR kinetic data yielded an association rate constant k_on = 7 × 10³ L/mol-s and a dissociation rate constant k_off = 10^-2s^-1, followed by a slower stabilization step (τ ∼ 400 s). Both DFS and SPR detected minimal interactions between αIIbβ3 and cHarGA demonstrating a key role for electrostatic interactions between the ligand aspartate and the integrin metal ion-dependent adhesion site (MIDAS). Our work provides new insights into the energy landscape of αIIbβ3's interactions with pharmacological and physiological ligands.

This manuscript describes a general and simple method to carbon-coat quantum dots (QDs) using microwave-assisted technology. By coating QDs with carbohydrates, you extend their application for bioimaging (in vitro and in vivo) as the metal core is now shielded by a protective coating layer. XRD and TEM verified that nanoparticles were coated with a layer of carbon-based material (reduced sucrose). In addition, we demonstrated the versatility of this approach by coating other types of nanoparticles (i.e. gold). UV–Visible spectroscopic analysis presented a red shift in absorbance after carbon coating which further confirmed that the surface of these nanoparticles was modified. QDs emission wavelength was not altered but experienced an increase in intensity. The carbon-coated QDs and gold nanoparticles generated in this study measured 14 nm and 60 nm, respectively.

We report an integrated nanochannel/nanoelectrode sensor for the detection of DNA using alternating currents. We find that DNA can be detected using platinum as the metal for the detecting electrodes, with a signal to noise ratio exceeding 10. We argue that the signal is at least in part electrochemical in nature, thus holds the promise to yield a sequence-dependent signal. However, we also find that for large voltages, DNA attaches irreversibly to the driving electrodes.

Bacterial deposition–transportation via a porous medium can be quantified by a dimensionless Tabor's parameter, μ, which accounts for the deformation of an elastic sphere in the presence of intersurface forces based on the classical Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. A concentrated solution of model spheres or bacterial strains passing through a packed sand column leads to water filtration, where the efficiency is measured by the efflux concentration, C/C₀, of particles. Experimental data of model latex spheres with ranges of size, ionic concentration and pH obtained by Elimelech, and our measurements of six different bacterial strains are analyzed. A strong correlation between C/C₀ and μ is found and can be used to predict deposition–transportation once the microscopic properties are known.

An immunoassay has been developed for the detection of bacterium Escherichia coli (E. coli) through β-Galactosidase (β-Gal). For developing an immunoassay on piezoelectric quartz crystal a polystyrene nanoparticle (PSNP) surface was developed by anchoring synthesized PSNPs (60 ± 5 nm) via self-assembled monolayer of p-aminothiophenol patterned on gold-coated quartz crystal. In order to make immunoassay specific to β-Gal, antibody specific to β-Gal (anti-β-Bal) was captured through physical attraction. On exposing this immunoassay to the β-Gal antigen (3.03 ng/ml), a strong detecting signal was observed, with simultaneous detachment of antibody from immunoassay as antigen–antibody complex. No appreciable change in the frequency shift, Δf, of quartz crystal was observed upon exposure to nonspecific Brucella antigen, confirming the specific behavior of immunoassay.

Microfabricated nanofluidic electrode assemblies (NEAs) with integrated palladium references were used to amperometrically monitor changes in pyocyanin concentration. Pyocyanin is an electroactive molecule that is produced by the opportunistic pathogen Pseudomonas aeruginosa and is directly linked to cellular processes that increase both robustness and virulence in this bacterium. This is the first time that pyocyanin has been measured in real time using microfabricated sensors. A linear response in faradaic current (R² = 0.96) was observed over a biomedically relevant range of pyocyanin concentrations (0–100 μM) while continuously measuring the current for 2 h. Measurement of the current that results from the repeated oxidation and reduction of pyocyanin at two closely spaced electrodes inside the device nanochannel yielded a 1.07 μM limit of detection without electrical isolation of the electrochemical cell. Since a reference electrode is integrated inside the nanofluidic channel of these sensors, they can potentially be employed to detect pyocyanin and other redox-active molecules in wide range of medical and environmental settings where space is limited. NEAs were also used with an external Ag/AgCl reference electrode to determine the concentration of pyocyanin in trypticase soy broth samples. This type of analysis is completed in less than 2 min and the detection limit was determined to be 441 nM.

The vasculature is regulated by various chemical and mechanical factors. Reproducing these factors in vitro is crucial for the understanding of the mechanisms underlying vascular diseases and the development of new therapeutics and delivery techniques. Microfluidic technology offers opportunities to precisely control the level, duration and extent of various cues, providing unprecedented capabilities to recapitulate the vascular microenvironment. In the first part of this article, we review existing microfluidic technology that is capable of controlling both chemical and mechanical factors regulating the vascular microenvironment. In particular, we focus on micro-systems developed for controlling key parameters such as oxygen tension, co-culture, shear stress, cyclic stretch and flow patterns. In the second part of this article, we highlight recent advances that resulted from the use of these microfluidic devices for vascular research.

Understanding cell–extracellular matrix interactions is crucial to the repair or replacement of cells, tissues and organs. The fate of cells can be dictated by the in vivo cellular microenvironment, which provides biophysical (topography), biomechanical (substrate elasticity and flow-induced forces) and biochemical (cytokines and growth factors) cues to regulate the phenotype and function of cells. For example, basement membranes manifest a complex three-dimensional (3D) texture with sizes in the nanometer range. In addition to inducing pronounced changes to cell morphology and, consequently, gene and protein expression, nanotopographical cues could potentially help induce the differentiation of stem cells into certain lineages. This review covers the commonly used techniques of engineering nanotopography, surveys cellular responses to nanotopography with the focus on the effects of dimensions, shape and order of nanotopographical cues relative to cell dimensions, and discusses possible mechanism by which cells sense nanotopography and the challenges in translating the mechanistic understanding of nanoscale modulation of cell behavior to regenerative medicine. Delineation of cell–matrix interactions in the physiological, 3D environment will help advance the field of regenerative medicine.

Nucleic acid (NA)-functionalized nanomaterials (NMs) have received considerable attention in recent years. The use of nucleic acid (DNA/RNA) for surface functionalization of NMs offers the ability to directly address desired targets and coat NMs with biocompatible polymers, such as poly [(ethylene)] glycol (PEG) and polyacrylamide (PA), enhancing the utility of these complexes in biomedicine. In particular, the target-specific recognition capacity of surface-functionalized NMs has opened up new avenues for disease diagnosis and therapy. This review focuses on the biological applications of a special type of nucleic acid, termed aptamer, conjugated with a variety of NMs for a wide spectrum of applications in nanobiomedicine.

Exposure to nanosized materials (specifically, materials with one dimension less than 100 nm) is nothing new. Humans have long been exposed to nanomaterials from various earth related processes, like forest fires and volcanoes, as well as naturally occurring events, such as sea spray. Due to the advent of modern nanotechnology research, however, the arrival of the industrial nanotechnology age is upon us where large quantities of various synthetic nanomaterials are formulated and exposed to humans on a daily basis. As such, there is an on-going need for more researchers to determine human and environmental toxicity of nanomaterials. This review paper will assess the current knowledge on the in vitro cytotoxicity and genotoxicity of nanomaterials while summarizing the exploration of nanotechnology within the specific world of biomaterials. An overview of material characterization studies as well as various biological assays currently used to evaluate cytotoxicity and genotoxicity will also be addressed. Specifically, after defining some basic definitions of biomaterials and biocompatibility, commonly used cytotoxicity assays are summarized, and some examples of nanomaterial cytotoxicity studies presented. Next, an understanding of genotoxicity assays and associated mechanisms with nanomaterials are presented. Finally, some future thoughts on nanobiomaterial (that is, nanomaterials used as biomaterials) cytotoxicity and genotoxicity are presented. Such an overview reflects a comprehensive effort to gain an understanding of the toxicity of nanobiomaterials at the molecular level requiring the use of a battery of toxicological assays. The purpose of this review article is to serve as reference for those new to the field of nanotoxicity and to encourage others to conduct accurate and meaningful nanotoxicity studies.