Current Nanoscience - Volume 4, Issue 1, 2008

Today, technologies based on magnetic nanoparticles (MNPs) are routinely applied to biological systems with diagnostic or therapeutic purposes. The paradigmatic example is the magnetic resonance imaging (MRI), a technique that uses the magnetic moments of MNPs as a disturbance of the proton resonance to obtain images. Similarly, magnetic fluid hyperthermia (MFH) uses MNPs as heat generators to induce localized cell death. The physical basis of these techniques relies on the interaction with external magnetic fields, and therefore the magnetic moment of the particles has to be maximized for these applications. Targeted drug-delivery based on ‘smart’ nanoparticles is the next step towards more efficient oncologic therapies, by delivering a minimal dose of drug only to the vicinity of the target. Current improvements in this fields relay on a) particle functionalization with specific ligands for targeting cell membrane receptors and b) loading MNPs onto cells (e.g., dendritic cells, T-cells, macrophages) having an active role in tumor grow. Here we review the current state of research on applications of magnetic carriers for cancer therapy, discussing the advances and drawbacks of both passive and targeted delivery of MNPs. The most promising strategies for targeted delivery of MNPs are analyzed, evaluating the expected impact on clinical MRI and MFH protocols.

Molecular imaging has emerged as a powerful tool to visualize molecular events of an underlying disease, sometimes prior to its downstream manifestation. This presents a whole new paradigm disease diagnosis and monitor treatment. Nanotechnology is another rapidly growing field that offers new materials with unique physical and chemical properties that may find broad application in biomedical research. The merging of nanotechnology with molecular imaging provides a versatile platform for novel design of nano-probes that will have tremendous potential to enhance the sensitivity, specificity, and signaling capabilities of various biomarkers in human diseases. In this review, the general construct and key characteristics of nanoprobes in the context of molecular imaging are highlighted. The various designs of nanoprobes based on their targeting mechanisms, strategies for contrast enhancement, multi-modality imaging and imaging/ therapy hybrid systems are outlined along with a discussion on the current status of imaging equipment design. Additionally, the potential challenges for adapting nanoprobes for molecular imaging including toxicity, biodistribution/pharmacokinetics, and synthetic feasibility are addressed.

Colloid science has now been reframed in advance form as nanotechnology. Novel nanoparticulate carrier systems could make an important impact on clinical practice, not only in the field of targeted drug delivery but also for the delivery of diagnostic agents, gene therapy and vaccine delivery as well. Polymer based nanoparticles are full of numerous advantages in delivery science but at the same time they suffer from toxicity considerations and problems in industrial scale up of the formulations. Lipid based carrier systems i.e. emulsions, liposomes etc. have been tried to solve such problems related to the delivery technology. Currently lipid-based nanoparticles gained much interest as they combine both the technology of lipid sciences and nanosciences, and hence may be better alternative carriers. Many aspects related to the development of solid lipid nanoparticles (SLNs) like production technology, effect of process parameters, selection of ingredients and route of delivery are important for the industrial applications of nanoscience. In the present review a detail discussion of methods of production of solid lipid nanoparticles, influence of ingredients of composition on product quality, therapeutic moiety effect, characterization parameters and effects of sterilization have been focused. Role of solid lipid nanoparticles for controlled and targeted drug delivery, utility as a novel transfection agent and their potential as adjuvant for vaccine delivery are summed up in addition. Clinical therapeutics of SLNs in terms of advantages and limitations of various routes of delivery of SLNs has also been explored for the further advancement of practical applications of solid lipid nanoparticles.

The solar energy conversion system based on photosynthesis is promising as alternative energy invention technology of the future. In this review, the photoenergy conversion system based on the photosensitization of major photosynthesis dye pigment molecule, chlorophyll immobilized onto titanium dioxide or assembled into surfactant micellar system are introduced. One is the photoinduced hydrogen production system with the system containing an electron donor reagent, an electron carrier reagent, hydrogen producing catalyst and chlorophyll molecule assembled in surfactant micellar system. The other one is the photovoltaic conversion system based on the chlorophyll or chlorophyll derivative molecules immobilized onto nanocrystalline TiO2 film electrode.

Poorly water-soluble compounds like albendazole with dissolution limited bioavailability need novel approaches for enhancement of bioavailability and therapeutic efficacy. The use of nanosuspension approach offers an opportunity to address the issues associated with BCS class II molecules. High pressure homogenization technique can be employed to produce drug nanocrystals with a number of advantages in comparison to other techniques such as nanoprecipitation, sonication, milling and high speed homogenization. The present study shows the feasibility of formulating a stable formulation of albendazole with minimum particle size through high pressure homogenization technique. To point out the influence and importance of identifying right stabilizer (s) and process parameters the studies such as influence of number of homogenizing cycles on particle size, sequence of mixing of ingredients on the physical characteristics of nanosuspensions and desorption studies was done. Selected nanosuspension formulations containing different stabilizers were lyophilized to convert into solid dosage forms. These studies had indicated that the aqueous dispersion of drug nanoparticles could be converted into stable solid dosage forms with out affecting the size on reconstitution.

Aim of this paper is to study the load-drug mechanism of polybutylcyanocrylate nanoparticles and the physical stability of albendazole- polybutylcyanocrylate nanoparticle (ABZ-PBCA-NP). The adsorption mechanism between albendazole with polybutylcyanocrylate nanoparticle in different phosphate buffer solution (PBS) were investigated with isothermadsorption method. The constants of stability constants of albendazole-loading nanoparticles were predicted by determined the conductance rate of nanoparticles colloid under predetermined temperature in interval time. At the same time, several stabilizer including polyvinyl pyrrolidone (PVP), carboxymethylcellulose sodium (CMC-Na) and hydroxoy-propyl methyl cellulose (HPMC) was screen for improving stability and fluidity of nanoparticle suspension. The results showed that the mechanism of drug-load in nanoparticle was fitted the Langmuir equation. The conductance rate indicated that load-drug nanoparticle in suspension was unstability due to nature aggregation tendency and improved by reinforced with 4% PVP in solution.

The field of molecular electronics measures the unique properties of individual molecular species in conductor-moleculeconductor junctions. We present here a brief review of molecular electronics as applied to biomolecules, with specific emphasis on the use of scanning probe technology in the assaying of biological molecular electronics. Three case studies from recent work within our group are described; two complimentary investigations of the redox-active yeast iso-1-cytochrome c and one of the large iron storage protein ferritin. The strengths and challenges of the use of scanning probe technology for the purpose of molecular electronics are also outlined. Particular emphasis is given to the potential of gating conductance and the perturbative effects of analysis.

In recent years, nanoscale self-assembled structures have attracted ever increasing attention because of their potential to act as molecular templates for the synthesis of novel materials, delivery vehicles for therapeutic agents, and compartments defined at the molecular level that provide environmental conditions conducive to specific chemical reactions. In this review, we will focus mostly on this latter application. Amphiphiles that self-assemble to yield nano-compartments such as micelles, reverse-micelles and liposomes, have been used to build nanoscale reactors that can effect chemical reactions through spatial co-localization of the reacting species. The reacting species may include the compartment building amphiphiles themselves. These nano-compartments provide not only the conditions for the reaction to occur, but also allow the buildup of complex reaction networks by retaining primary reaction products which may in turn be capable of additional reactions. Ultimately, such complex systems could also serve as starting points for minimal artificial cells, i.e. protocells which would be highly simplified versions of biological cells and which might be engineered for specific tasks related to therapeutic and diagnostic applications. We will report on advances in the design of these chemical self-assembled systems and the challenges that still lie ahead.

Silica encapsulated CdSe quantum dots (QDs) with a relatively strong photoluminescence were prepared using 3- mercaptopropyl trimethoxysilane by Stober method at room temperature. The effect of pH of the physiological saline on the photoluminescence was investigated while the nanocomposites were dispersed in it. The results show a comparatively high stability of the luminescence. The thermal stability of the photoluminescence of the composite nanoparticles was also studied. After annealing at 60°C for 2 h, the photoluminescence was kept constant. Then, after annealing at 200°C for 2 h, the photoluminescence was promoted by over 10 times with a marked blue-shifted emission. In addition, the stabilization of the core-shell structured composites against the intense illumination was investigated through the transmission electron microscopy (TEM) observation and the luminescence measurement.

In recent years, increasing attention has been paid for the construction of optically active nanomaterials. In particular, monolayer- protected gold nanoclusters are attractive for such systems. To date, optically active gold nanoclusters have been prepared by using chiral adsorbates or surface modifiers. In general, two major explanations have been proposed to interpret the optical activity: The first assumes a chiral core as a result of lattice distortion caused by the adsorbate. The other involves an achiral core with chirality induced by a chiral adsorption pattern or by dissymmetric fields (vicinal effect) from the chiral adsorbates. This mini-review gives an outline of the syntheses and chiroptical properties of the chiral monolayer-protected gold nanoclusters on the basis of our recent work as well as the other groups' studies.

The structures and the nonbonded intermolecular interactions of the endohedral and exohedral 4Å-diameter carbon nanotubenoble gas clusters, NG@CNT (NG = He, Ne, Ar, Kr, and Xe) are evaluated and calculated using the atom-atom potential method. The complexing energies are determined with a Lennard-Jones model. Complexing energies are significantly dependent on azimuthal angle. Endohedral complexes are more stable; consequently, noble gases can be accommodated into 4 Å diameter carbon nanotubes. While slightly larger atoms Ar, Kr, and Xe atoms are more stable.

Formulation studies of nano- and microparticles are a rapidly developing area in pharmaceutical sciences. Bioavailability of poorly water-soluble drugs may be increased by administrating them as nanoparticle formulations. Drug targeting to specific body sites has also been studied intensively (e.g. cancer chemotherapy). In order to ensure the repeatability of the formulation processes and the efficacy/ stability of the formed particles, thorough characterization of the formulations and particles is crucial. The importance of analytical techniques and even during the process analysis has been highlighted by drug authorities (e.g. FDA) with the PAT approach. Minor deviations, e.g., in particle size/shape, surface charge or aggregation tendency, may play a significant role in their behavior in the body. The very small size of the nanoparticles imposes extra demands for the characterization techniques. In this review, the most commonly used and most important analysis methods to characterize the micro- and nanoparticles are discussed with critical view on the applicability and limitations of the methodologies. Some techniques are well known for the researchers in the small particle area (e.g. microscopic techniques, thermal analysis, zeta potential, dissolution rate), but also more rarely used and new techniques (e.g. surface tension/pressure measurements, spectroscopic methods) are taken into account.

The hairpin structure of DNA molecules have been widely employed for a variety of biosensors and nanoscale molecular assembly applications. For example, the commonly known molecular beacons can report the presence of specific nucleic acids in homogeneous solutions with high accuracy. Recently, Smith et al. proposed to induce hairpin formation through the sequence-specific binding of a small-molecule ligand G-G mismatch. Not only did this make the control of the hairpin formation flexible, but more important the induced hairpin still keeps a high sensitivity to specific hybridization. In this paper, we simulate the working process of logical XOR gates based on induced hairpin formation.

Around 500,000 people have total joint (including hip and knee) replacement surgeries each year. However, current joint implants last only 10 to 15 years before failing. Undoubtly because of this, many patients have to go through a revision surgery due to the failure of bone implants. The main reason for implant failure is aseptic loosening of the implant from juxtaposed bone. In this light, polymethyl methacrylate (PMMA) has been used widely in orthopedics to improve the bonding between the implant and bone. In total hip replacement procedures, PMMA cement is located at the bone-implant interface and plays an important role in inhibiting the aseptic loosening processes. PMMA cement is associated with several drawbacks that limit its efficacy (such as strong exothermic reactions, weak radiopacity and poor fatigue strength; all leading to insufficient bonding to bone). With an expectation of increased revision surgeries and patients receiving orthopedic implants in the coming years, the emphasis of joint replacement research needs to be focused on improving the mechanical and biocompatibility properties of bone cements. As nanotechnology has been extensively used to improve mechanical and surface properties of implant materials, it certainly provides a unique opportunity to modify the material properties of currently used bone cements in a more precise manner. This article reviews nanotechnology-based advancements made to PMMA cement and bioactive cements (Bis-GMA cement and calcium phosphate cement (CPC)). A discussion of accomplishments, potentials and challenges for the application of nanotechnology in bone cements then follows.