Dynamic Surface Properties of Fullerenol Solutions

Potential Medical Use of Fullerenols After Two Decades of Oncology Research

Fullerenes are carbon molecules that are found in nature in various forms. They are composed of hexagonal and pentagonal rings that create closed structures. Almost 4 decades ago, fullerenes were identified in the form of C60 and C70, and following the award of the Nobel Prize in Chemistry for this discovery in 1996, many laboratories started working on their water-soluble derivatives that could be used in different industries, including pharmaceutical industries. One of the first fullerene forms that was the focus of different research groups was fullerenol, C60(OH)n (n  =  2-44). Both in-vitro and in-vivo studies have shown that polyhydroxylate fullerene derivatives can potentially be used as either antioxidative agents or cytostatics (depending on their co-administration, forms, and concentration/dose) in biological systems. The current review aimed to present a critical view of the potential applications and limitations of fullerenols in oncology, as understood from the past 2 decades of research.

Interfacial Dynamics of Adsorption Layers as Supports for Biomedical Research and Diagnostics

The input of chemical and physical sciences to life sciences is increasingly important. Surface science as a complex multidisciplinary research area provides many relevant practical tools to support research in medicine. The tensiometry and surface rheology of human biological liquids as diagnostic tools have been very successfully applied. Additionally, for the characterization of pulmonary surfactants, this methodology is essential to deepen the insights into the functionality of the lungs and for the most efficient administration of certain drugs. Problems in ophthalmology can be addressed using surface science methods, such as the stability of the wetting films and the development of artificial tears. The serious problem of obesity is fast-developing in many industrial countries and must be better understood, while therapies for its treatment must also be developed. Finally, the application of fullerenes as a suitable system for detecting cancer in humans is discussed.

Surface Activity and Aggregation Behavior of Polyhydroxylated Fullerenes in Aqueous Solutions

Polyhydroxylated fullerene (PHF) surface activity and aggregation behavior at the air-water interface were examined using surface tension and resonance-enhanced second harmonic generation (SHG). Surface tension data showed that PHFs are surface active with a limiting surface excess corresponding to 130 Ų/molecule in aqueous (Millipore water) solutions. Increasing the solution-phase ionic strength (through the addition of NaCl) reduces the PHF surface excess. Conductivity measurements show that PHFs carry a single charge, presumably negative. Surface-specific SHG experiments show a small but measurable fixed wavelength, nonlinear response from solutions having surface excess coverages as low as ∼400 Ų/molecule. The SHG response of PHF solutions in the low-concentration limit shows unexpected behavior, implying that at bulk concentrations below 0.06 mg/mL, PHF monomers adsorb to the surface and interfere destructively with the intrinsic nonlinear susceptibility of the aqueous/vapor interface, leading to a ∼75% reduction in the SH signal. Above a PHF concentration of 0.0.06 mg/mL, the SH signal begins to rise in the Millipore and 50 mM NaCl solutions but remains very low in the 500 mM NaCl solutions. From this behavior, we infer that an increased nonlinear optical response is due to adsorbed aggregates.

Carbon Nanoparticle-Induced Changes to Lipid Monolayer Structure at Water-Air Interfaces

Surface specific vibrational spectroscopy experiments together with surface tension measurements and spectroscopic ellipsometry data were used to characterize the effects of soluble carbon particulates on compressed and partially compressed lipid monolayers adsorbed to the water-air interface. The lipid monolayers consisted of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DPPC), and measurements were made for both tightly packed monolayers (40 Ų/molecule) and monolayers in their liquid condensed state (55 Ų/molecule). Langmuir trough data show that very small amounts of PHF (0.0075 mg/mL or 6.4 × 10^-6 M) decrease lipid film compressibility. This finding supports a cooperative adsorption mechanism whereby the soluble PHFs are drawn to the surface and associate with the insoluble DPPC monolayer. Excess free energies (ΔG_mix^E) were positive, consistent with the cooperative adsorption mechanism, and although the excess free energies are small (≤1 kJ/mol), adsorbed PHF has measurable effects on monolayer structure. Further support for the cooperative adsorption mechanism at the water-air interface comes from vibrational sum frequency generation (VSFG) experiments. Low PHF concentrations (≤0.06 mg/mL) increase DPPC acyl chain ordering in liquid condensed lipid films and decrease DPPC acyl chain ordering and film thickness in tightly packed lipid films.

The Effect of the Open Vase-like Microcapsules Formation with NiFe Double-Hydroxide Walls during Hydrolysis of the Mixture NiSO4 and FeSO4 Salt Solution Microdroplets Deposited on the Alkaline Solution Surface

In this work, the conditions for the synthesis of open vase-like microcapsules with a size of 1–5 μm and 20–40 nm walls of NiFe0.3(OH)x layered double hydroxide were studied. These microcapsules were obtained by the rapid hydrolysis of microdroplets of a solution of a mixture of NiSO4 and FeSO4 salts at the surface of an alkali solution. A hypothetical model of successive chemical processes occurring at the interface during synthesis is presented. The features of the “rim” formation around each microcapsule hole from the wall material with a peculiar nozzle-like shape are noted. These microcapsules can be transferred to the surface of a nickel foil using the Langmuir–Schaefer (LS) method. During the transfer process, they are fixed to the surface in an oriented position with a “rim” that contacts the nickel surface. It was established that electrodes made of such a foil with a layer of microcapsules exhibit active electrocatalytic properties in the oxygen evolution reaction during the electrolysis of water in an alkaline medium.

Fullerenol Nanoparticles Eradicate Helicobacter pylori via pH-Responsive Peroxidase Activity

Helicobacter pylori (H. pylori) eradication by antibiotics and proton pump inhibitor treatment is limited by the low pH microenvironment in the stomach and can lead to antibiotic resistance. We fabricated fullerenol nanoparticles (FNPs) with varied chemical structures responding to a pinacol rearrangement of vicinal hydroxyl to form carbonyls in low pH environments. An obvious increase in C═O/C-O was induced in low pH and was positively correlated with a peroxidase-like activity. The FNPs exerted an excellent effect on H. pylori eradication in vitro and in vivo because of their peroxidase-like activity. FNP treatment of a H. pylori biofilm revealed that FNPs broke down polysaccharides in cell wall components, resulting in collapse of the bacteria. The cycles of FNPs combining and dissociating with the peroxidase substrate were detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and confirmed that FNPs enhance peroxidase-like activity. Further, the isothermal titration calorimetry results showed that FNPs with more C═O/C-O had greater affinity to bind the peroxidase substrates. Therefore, we suggest that varied C═O/C-O serves as a switch to respond to low pH in the stomach to kill H. pylori by inducing a peroxidase-like activity. FNPs can also overcome the challenge of antibiotic resistance to achieve H. pylori eradication in the stomach.

Network Formation of DNA/Polyelectrolyte Fibrous Aggregates Adsorbed at the Water-Air Interface

It is discovered that complexes of DNA and hydrophobically modified polyelectrolytes form a rigid network of threadlike or fibrous aggregates at the liquid-gas interface whose morphology can dramatically affect the mechanical properties. While mixed solutions of DNA and poly(N,N-diallyl-N,N-dimethylammonium chloride) (PDADMAC) exhibit no notable surface activity, the complexes formed from DNA with poly(N,N-diallyl-N-butyl-N-methylammonium chloride) are surface-active, in contrast to either of the separate components. Further, complexes of DNA and poly(N,N-diallyl-N-hexyl-N-methylammonium chloride) (PDAHMAC) with its longer hydrophobic side chains exhibit pronounced surface activity with values of surface pressures up to 16 mN/m and dynamic surface elasticity up to 58 mN/m. If the PDAHMAC nitrogen to DNA phosphate molar ratio, N/P, is between 0.6 and 3, abrupt compression of the adsorption layer leads unexpectedly to a noticeable decrease of the surface elasticity. The application of imaging techniques reveals that this effect is a consequence of the destruction of a rigid network of threadlike DNA/polyelectrolyte aggregates at the interface. The toroidal aggregates, which are typical for the bulk phase of DNA/PDADMAC solutions in this range of N/P ratios, are not observed in the surface layer. The observed link between the mechanical properties and interfacial morphology of surface-active complexes formed from DNA with hydrophobically modified polyelectrolytes indicates that tuning polyelectrolyte hydrophobicity in these systems may be a means to develop their use in applications ranging from nonviral gene-delivery vehicles to conductive nanowires.