Dmitry A. Gorin

Anticancer drug delivery system based on calcium carbonate particles loaded with a photosensitizer.

In photodynamic therapy (PDT), photosensitizers are required to arrive in high concentrations at selective targets like cancer cells avoiding toxicity in healthy tissue. In this work, we propose the application of porous calcium carbonate carriers in the form of polycrystalline vaterite for this task. We investigated the loading efficiency for the photosensitizer Photosens in vaterite micro- and nanocarriers. A possible release mechanism depending on the surrounding pH was studied, showing a fast degradation of the carriers in buffers below pH7. These results hold out the prospect of a novel PDT drug delivery system. Variation of particle size or additional coatings allow custom-design of workload release curves. An intrinsic cancer-sensitivity can be expected from the pH-dependent release in the acidic microenvironment of cancer tissue.

Selective ultrasonic cavitation on patterned hydrophobic surfaces.

Ultrasound can create cavitation bubbles that upon collapse cause extreme temperatures and pressures. Sonochemistry therefore carries much promise as an environmentally friendly method to carry out chemical processes at ultrahigh temperatures (ca. 5000 K), and pressures (ca. 1000 atm), but with a reactor at near-ambient conditions. The extraordinarily high cooling rates also enable preparation of materials far from equilibrium; for example, nanoparticles for catalysis, optics, and electronics. Herein we demonstrate semiquantitatively that nucleation of gas bubbles at surfaces can be controlled by the surface energy. Patterning of surfaces by molecular assembly thus enables formation of lateral patterns with well-defined nanoscopic roughness and chemistry, opening possibilities for new surface chemistry and physical studies of defined bubble nucleation. A model is presented that takes into account the competition between surface energy and the acoustic energy to inhibit and induce cavitation, respectively. In recent years, sonochemistry has developed from an exotic art into a most promising discipline in materials science. The process has also been used to create defined surfaces with specific roughness and surface chemistry for strong adhesion or for defined electrochemistry and catalysis. It is also used routinely in industry and also in most laboratories for the cleaning of surfaces. However, the question is only rarely asked as to whether the surface also influences the cavitation process. It should be possible to control surface treatment by the control of surface energies. This should not only hold for planar surfaces, but also for surfaces of microparticles and their dispersion and for the treatment of mixed solids where one component should be dispersed, for example, in separation chemistry or in preparing microporous solids. A most promising way to access the influence of surface energies is to make use of microprinting techniques. In this way, micrometer-sized hydrophobic areas can be prepared next to hydrophilic regions and maintain bulk conditions, thus allowing the two types of surfaces to be compared under identical conditions. This also holds for the acoustic pressure, as ultrasonic wavelengths used for sonochemistry are typically longer than 1 mm. These conditions and techniques are applied herein: we will concentrate on understanding the mechanism, but keep in mind that this is also a way to prepare microroughnesses and surface chemistry on well-defined and preselected areas, which is useful for a broad range of applications. Scenarios that compare bubble formation on hydrophobic and hydrophilic surfaces and in the bulk are given in Figure 1. To explain the surface influence on bubble

Nanoplasmonic Chitosan Nanofibers as Effective SERS Substrate for Detection of Small Molecules

The use of surface enhanced Raman spectroscopy (SERS) is limited by low reproducibility and uniformity of the response. Solving these problems can turn the laboratory use of SERS into real-world application. In this regard, soft SERS-active substrates can enable portable instrumentation and reduce costs in the fabrication of SERS-based sensors. Here, plasmonic free-standing films made of biocompatible chitosan nanofibers and gold nanoparticles are engineered by a simple protocol varying the concentration of chloroauric acid. The concentration and distribution of gold nanoparticles in films are controlled in a predictable way, and SERS spectra for the standard 2-naphthalenethiol with concentration less than 10(-15) M are acquired in a reproducible way. The statistical analysis reveals a relatively high and locally uniform performance of SERS with an enhancement factor of 2 × 10(5) for 86% of the points on the imaged area of the SERS substrate. Potential SERS detection of small molecules, both Rhodamine 6G and d-Glucose, in the micromolar range is demonstrated.

Multilayer Capsules of Bovine Serum Albumin and Tannic Acid for Controlled Release by Enzymatic Degradation

With the purpose to replace expensive and significantly cytotoxic positively charged polypeptides in biodegradable capsules formed via Layer-by-Layer (LbL) assembly, multilayers of bovine serum albumin (BSA) and tannic acid (TA) are obtained and employed for encapsulation and release of model drugs with different solubility in water: hydrophilic-tetramethylrhodamine-isothiocyanate-labeled BSA (TRITC-BSA) and hydrophobic 3,4,9,10-tetra-(hectoxy-carbonyl)-perylene (THCP). Hydrogen bonding is proposed to be predominant within thus formed BSA/TA films. The TRITC-BSA-loaded capsules comprising 6 bilayers of the protein and polyphenol are benchmarked against the shells composed of dextran sulfate (DS) and poly-l-arginine (PARG) on degradability by two proteolytic enzymes with different cleavage site specificity (i.e., α-chymotrypsin and trypsin) and toxicity for murine RAW264.7 macrophage cells. Capsules of both types possess low cytotoxicity taken at concentrations equal or below 50 capsules per cell, and evident susceptibility to α-chymotrypsin resulted in release of TRITC-BSA. While the BSA/TA-based capsules clearly display resistance to treatment with trypsin, the assemblies of DS/PARG extensively degrade. Successful encapsulation of THCP in the TRITC-BSA/TA/BSA multilayer is confirmed, and the release of the model drug is observed in response to treatment with α-chymotrypsin. The thickness, surface morphology, and enzyme-catalyzed degradation process of the BSA/TA-based films are investigated on a planar multilayer comprising 40 bilayers of the protein and polyphenol deposited on a silicon wafer. The developed BSA/TA-based capsules with a protease-specific degradation mechanism are proposed to find applications in personal care, pharmacology, and the development of drug delivery systems including those intravenous injectable and having site-specific release capability.

Nanoengineered colloidal probes for Raman-based detection of biomolecules inside living cells.

Gold nanoparticle aggregate carbon nanotube functionalized colloidal particles serve as an efficient platform for probing the intracellular environment. The probes provide the means of effective localization of signal and detection of molecular fingerprints of biomolecules in living cells. The approach demonstrated in this work opens significant opportunities in molecular imaging as well as intracellular sensing and trafficking.

Controlled Effect of Ultrasonic Cavitation on Hydrophobic/Hydrophilic Surfaces

Controlling cavitation at the solid surface is of increasing interest, as it plays a major role in many physical and chemical processes related to the modification of solid surfaces and formation of multicomponent nanoparticles. Here, we show a selective control of ultrasonic cavitation on metal surfaces with different hydrophobicity. By applying a microcontact printing technique we successfully formed hydrophobic/hydrophilic alternating well-defined microstructures on aluminium surfaces. Fabrication of patterned surfaces provides the unique opportunity to verify a model of heterogeneous nucleation of cavitation bubbles near the solid/water interface by varying the wettability of the surface, temperature and ultrasonic power. At the initial stage of sonication (up to 30 min), microjets and shock waves resulting from the collapsing bubbles preferably impact the hydrophobic surface, whereas the hydrophilic areas of the patterned Al remain unchanged. Longer sonication periods affect both surfaces. These findings confirm the expectation that higher contact angle causes a lower energy barrier, thus cavitation dominates at the hydrophobic surfaces. Experimental results are in good agreement with expectations from nucleation theory. This paper illustrates a new approach to ultrasound induced modification of solid surfaces resulting in the formation of foam-structured metal surfaces.

Effect of microwave radiation on polymer microcapsules containing inorganic nanoparticles

The effect of microwave radiation on polymer microcapsules containing inorganic nanoparticles has been studied. The samples were exposed to 2.45 and 8.208 GHz microwaves of variable power. The data of scanning electron microscopy show that the character of microwave action upon polymer microcapsules depends on their composition and on the frequency and power of radiation.

Liposomes loaded with hydrophilic magnetite nanoparticles: Preparation and application as contrast agents for magnetic resonance imaging

Magnetic fluid-loaded liposomes (MFLs) were fabricated using magnetite nanoparticles (MNPs) and natural phospholipids via the thin film hydration method followed by extrusion. The size distribution and composition of MFLs were studied using dynamic light scattering and spectrophotometry. The effective ranges of magnetite concentration in MNPs hydrosol and MFLs for contrasting at both T2 and T1 relaxation were determined. On T2 weighted images, the MFLs effectively increased the contrast if compared with MNPs hydrosol, while on T1 weighted images, MNPs hydrosol contrasting was more efficient than that of MFLs. In vivo magnetic resonance imaging (MRI) contrasting properties of MFLs and their effects on tumor and normal tissues morphology, were investigated in rats with transplanted renal cell carcinoma upon intratumoral administration of MFLs. No significant morphological changes in rat internal organs upon intratumoral injection of MFLs were detected, suggesting that the liposomes are relatively safe and can be used as the potential contrasting agents for MRI.

A new approach to nucleation of cavitation bubbles at chemically modified surfaces

Cavitation at the solid surface normally begins with nucleation, in which defects or assembled molecules located at a liquid-solid interface act as nucleation centers and are actively involved in the evolution of cavitation bubbles. Here, we propose a simple approach to evaluate the behavior of cavitation bubbles formed under high intensity ultrasound (20 kHz, 51.3 W cm(-2)) at solid surfaces, based on sonication of patterned substrates with a small roughness (less than 3 nm) and controllable surface energy. A mixture of octadecylphosphonic acid (ODTA) and octadecanethiol (ODT) was stamped on the Si wafer coated with different thicknesses of an aluminium layer (20-500 nm). We investigated the growth mechanism of cavitation bubble nuclei and the evolution of individual pits (defects) formed under sonication on the modified surface. A new activation behavior as a function of Al thickness, sonication time, ultrasonic power and temperature is reported. In this process cooperativity is introduced, as initially formed pits further reduce the energy to form bubbles. Furthermore, cavitation on the patterns is a controllable process, where up to 40-50 min of sonication time only the hydrophobic areas are active nucleation sites. This study provides a convincing proof of our theoretical approach on nucleation.

Impact of magnetite nanoparticle incorporation on optical and electrical properties of nanocomposite LbL assemblies

Optical and electrical properties of polyelectrolyte/iron oxide nanocomposite planar films on silicon substrates were investigated for different amount of iron oxide nanoparticles incorporated in the films. The nanocomposite assemblies prepared by the layer-by-layer assembly technique were characterized by ellipsometry, atomic force microscopy, and secondary ion mass-spectrometry. Absorption spectra of the films reveal a shift of the optical absorption edge to higher energy when the number of deposited layers decreases. Capacitance-voltage and current-voltage measurements were applied to study the electrical properties of metal-oxide-semiconductor structures prepared by thermal evaporation of gold electrodes on nanocomposite films. The capacitance-voltage measurements show that the dielectric constant of the film increases with the number of deposited layers and the fixed charge and the trapped charge densities have a negative sign.