Cavity-enhanced optical detection of carbon nanotube Brownian motion

Optical cavities with small mode volume are well-suited to detect the vibration of sub-wavelength sized objects. Here we employ a fiber-based, high-finesse optical microcavity to detect the Brownian motion of a freely suspended carbon nanotube at room temperature under vacuum. The optical detection resolves deflections of the oscillating tube down to 50pm/Hz^1/2. A full vibrational spectrum of the carbon nanotube is obtained and confirmed by characterization of the same device in a scanning electron microscope. Our work successfully extends the principles of high-sensitivity optomechanical detection to molecular scale nanomechanical systems.Comment: 14 pages, 11 figure

Microscopic nanomechanical dissipation in gallium arsenide resonators

We report on a systematic study of nanomechanical dissipation in high-frequency (approximatively 300 MHz) gallium arsenide optomechanical disk resonators, in conditions where clamping and fluidic losses are negligible. Phonon-phonon interactions are shown to contribute with a loss background fading away at cryogenic temperatures (3 K). Atomic layer deposition of alumina at the surface modifies the quality factor of resonators, pointing towards the importance of surface dissipation. The temperature evolution is accurately fitted by two-level systems models, showing that nanomechanical dissipation in gallium arsenide resonators directly connects to their microscopic properties. Two-level systems, notably at surfaces, appear to rule the damping and fluctuations of such high-quality crystalline nanomechanical devices, at all temperatures from 3 to 300K

Role of Neurotrophins in Orofacial Pain Modulation: A Review of the Latest Discoveries

Orofacial pain represents a multidisciplinary biomedical challenge involving basic and clinical research for which no satisfactory solution has been found. In this regard, trigeminal pain is described as one of the worst pains perceived, leaving the patient with no hope for the future. The aim of this review is to evaluate the latest discoveries on the involvement of neurotrophins in orofacial nociception, describing their role and expression in peripheral tissues, trigeminal ganglion, and trigeminal nucleus considering their double nature as “supporters” of the nervous system and as “promoters” of nociceptive transmission. In order to scan recent literature (last ten years), three independent researchers referred to databases PubMed, Embase, Google Scholar, Scopus, and Web of Science to find original research articles and clinical trials. The researchers selected 33 papers: 29 original research articles and 4 clinical trials. The results obtained by the screening of the selected articles show an interesting trend, in which the precise modulation of neurotrophin signaling could switch neurotrophins from being a “promoter” of pain to their beneficial neurotrophic role of supporting the nerves in their recovery, especially when a structural alteration is present, as in neuropathic pain. In conclusion, neurotrophins could be interesting targets for orofacial pain modulation but more studies are necessary to clarify their role for future application in clinical practice

Interaction of mucins with bioinspired polymers and drug delivery particles

Mucins are glycoproteins with high molecular weight and an abundance of negatively charged oligosaccharide side chains, representing the main components in the mucous gels apart from water. Mucin structure consists of a flexible backbone (mainly serine and threonine residues) which serves as anchoring points for oligosaccharide side chains, and hydrophobic \u201cnaked domains\u201d enriched in cysteine residues. The latter can form inter-molecular bonds via disulphide links, promoting mucin association in solution. Therefore, mucins can establish adhesive interactions with particulates/biomacromolecules via electrostatic interactions, van der Waals forces, hydrophobic forces, hydrogen bonding, or chain entanglement. Mucosal drug delivery vehicles can either penetrate rapidly or establish prolonged contact. However, their development is of great challenge because little is still known about the interactions between mucin and other macromolecules. We are currently working on a comprehensive study of the interaction between mucin and macromolecules of interest for pharmaceutical developments by complementary techniques. To this scope, we employ biocompatible natural and synthetic polymers with different physical-chemical characteristics. Among them, linear polyamidoamines with amphoteric character are particularly interesting for their cyto-biocompatibility. It is indeed crucial to characterise such interactions not only in the bulk but also at the interface, since complexation between mucins and biomacromolecules takes place close to the cell membrane surface. Moreover, the strategy to overcome mucus barrier and achieve long retention time in the cell surface is to develop nano-agents which can effectively penetrate the mucus layer and accumulate at the epithelial surface. In this framework we present preliminary investigations in the bulk by small angle x-ray scattering (SAXS) and at the solid-liquid interface by employing quartz crystal microbalance (QCM-D)

Model cell membrane interaction with a bioinspired amphoteric polymer

We present recent investigation by means of nanoscale techniques on biocompatible linear polyamidoamines with amphoteric character, namely AGMA1 and ARGO7. These polymers have been shown of extremely promising and already proved medical interest, comprising their strong protection actions against virus infection, mainly papilloma and herpes and the extremely low toxicity of their DNA complexes, with respect to other used polymers such as PEI and protamine, applied in nanovector design for gene delivery. Our studies focus on the most important of these polymers, AGMA1, a prevailingly cationic 4-aminobutylguanidine-deriving PAA, whose mechanism of action is so far not fully understood. The current understanding is that its interaction with cell surfaces by means of glycosaminoglycans (HSPG) has a major role in its protective action against viruses. Yet, AGMA1 is active also against HPV-31, whose attachment does not appear to be dependent on HSPG. HPV-31, whose attachment does not appear to be dependent on HSPG. Therefore, AGMA1 binds other (as yet unidentified) receptors on the cell surface. As the known recipient is the HS carbohydrate moiety, other sugars rich membrane components have been proposed as probable AGMA1 target. Therefore, to shed a light on the mechanism of interaction of the polymer with sugar containing biologically relevant molecules, not HS, we have investigated AGMA1 in interaction with glycophyngolipids, Specifically, we studied multicomponent symmetric vesicles enriched in ganglioside GM1 built to mimic biological membrane domains, in the presence of AGMA1, At physiological pH, electrostatic effects should be the relevant interactions between GM1 and AGMA1. Taking advantage of the same mechanism we investigated the possibility of building lipid based core-shell particles to vehiculate AGMA1/siRNA complexes. Moreover, since it is probable that AGMA1 interacts with the barrier of mucus which cover the involved tissue we have extended our investigations also to mucin, constituting the biological barrier to the target tissues of the medical application of the polymers

Decoration of nanovesicles with pH (low) insertion peptide (pHLIP) for targeted delivery

Acidity at surface of cancer cells is a hallmark of tumor microenvironments, which does not depend on tumor perfusion, thus it may serve as a general biomarker for targeting tumor cells. We used the pH (low) insertion peptide (pHLIP) for decoration of liposomes and niosomes. pHLIP senses pH at the surface of cancer cells and inserts into the membrane of targeted cells, and brings nanomaterial to close proximity of cellular membrane. DMPC liposomes and Tween 20 or Span 20 niosomes with and without pHLIP in their coating were fully characterized in order to obtain fundamental understanding on nanocarrier features and facilitate the rational design of acidity sensitive nanovectors. The samples stability over time and in presence of serum was demonstrated. The size, ζ-potential, and morphology of nanovectors, as well as their ability to entrap a hydrophilic probe and modulate its release were investigated. pHLIP decorated vesicles could be useful to obtain a prolonged (modified) release of biological active substances for targeting tumors and other acidic diseased tissues