Ultrasmall superparamagnetic iron oxide nanoparticles with a size <5 nm are emerging nanomaterials for their excellent biocompatibility, chemical stability, and tunable surface modifications. The applications explored include dual-modal or multi-modal imaging, drug delivery, theranostics and, more recently, magnetic resonance angiography. Good biocompatibility and biosafety are regarded as the preliminary requirements for their biomedical applications and further exploration in this field is still required. We previously synthesized and characterized ultrafine (average core size of 3 nm) silica-coated superparamagnetic iron oxide fluorescent nanoparticles, named sub-5 SIO-Fl, uniform in size, shape, chemical properties and composition. The cellular uptake and in vitro biocompatibility of the as-synthesized nanoparticles were demonstrated in a human colon cancer cellular model. Here, we investigated the biocompatibility of sub-5 SIO-Fl nanoparticles in human Amniotic Mesenchymal Stromal/Stem Cells (hAMSCs). Kinetic analysis of cellular uptake showed a quick nanoparticle internalization in the first hour, increasing over time and after long exposure (48 h), the uptake rate gradually slowed down. We demonstrated that after internalization, sub-5 SIO-Fl nanoparticles neither affect hAMSC growth, viability, morphology, cytoskeletal organization, cell cycle progression, immunophenotype, and the expression of pro-angiogenic and immunoregulatory paracrine factors nor the osteogenic and myogenic differentiation markers. Furthermore, sub-5 SIO-Fl nanoparticles were intravenously injected into mice to investigate the in vivo biodistribution and toxicity profile for a time period of 7 weeks. Our findings showed an immediate transient accumulation of nanoparticles in the kidney, followed by the liver and lungs, where iron contents increased over a 7-week period. Histopathology, hematology, serum pro-inflammatory response, body weight and mortality studies demonstrated a short- and long-term biocompatibility and biosafety profile with no apparent acute and chronic toxicity caused by these nanoparticles in mice. Overall, these results suggest the feasibility of using sub-5 SIO-Fl nanoparticles as a promising agent for stem cell magnetic targeting as well as for diagnostic and therapeutic applications in oncology.

Flame sensing and early fire detection are primary features in modern security and surveillance systems. Optical detection systems are widely developed and offer the highest sensitivity and selectivity but they are still expensive and show a high power budget. Here we propose a low-cost, low-power flame detector based on PbS colloidal quantum dots. We show detector operation with a 21 nW total power dissipation and the ability to detect the flame of a candle at 20 m with a 5 dB signal to noise ratio (SNR).

We report on the noise characterization of photoconductors based on PbS colloidal quantum dots. The devices operate in the near infrared region with peak responsivity exceeding 70 A/W at 1.3 mu m at low optical intensity and low voltage bias. The large responsivity, combined with the low dark current of high resistance devices, provides a specific detectivity D* as large as 10(11) cm Hz(1/2)W(-1). The noise characteristics are investigated using noise current spectra measured at different biases both in dark and under optical excitation. The analysis revealed that the noise is clearly dominated by the flicker component up to 100 kHz. The noise performance is investigated at different optical intensities and for different device dimensions and voltage biases.

We report on a novel optical fire detector based on a PbS colloidal quantum dot photodetector. The sensor is realized with a simple, cost effective, drop casting technique. The photodetector is characterized in terms of its electrical characteristics, responsivity, and specific detectivity to monochromatic light. We demonstrate effective indoor fire detection at a distance exceeding 20 m with a 120° field of view. We also show a twofold improvement of the detector signal to noise ratio exploiting a short focal lens.

In this letter, we report on high responsivity fire detectors based on PbS colloidal quantum dots photoconductors. The devices operate in the near infrared and are equipped with a visible light silicon filter for wavelength selectivity. Devices are fabricated by a simple, low cost, and silicon compatible process based on drop casting of a ligand exchanged solution of PbS nanoparticles. The photodetectors exhibit responsivity as high as 20 A/W at 1-V bias. We exploit the combination of their high responsivity and spectral response for the development of a novel fire detector able to detect a small flame at a distance exceeding 15 m in ambient illumination.

Nanoparticles (NPs) made up of components between 1 nm and 100 nm in size and specifically magnetic iron oxide nanoparticles (IONPs), approved by Food and Drug Administration (FDA), have been extensively studied and have attracted much interest for their intriguing properties employable in a wide range of biomedical applications . NPs are used for diagnosis, prevention and treatment of diseases as much as for tissue engineering and regenerative medicine applications. These implementations demand the cross communication among different disciplines for the success of new therapies in restoring and regenerating the normal function of damaged cells, organs and tissues. The scientific rationale for the present multidisciplinary study is suggested by the need to design innovative and safe strategies to deal with human diseases. We synthetized and characterized ultrafine 3 nm superparamagnetic water-dispersible nanoparticles, prepared by an "arrested precipitation strategy". By a facile and inexpensive one-pot approach, nanoparticles were coated with silica to prevent their degradation/aggregation and to increase their surface functionalization, and contemporarily labelled with fluorescein isothiocyanate (FITC) dye to visualize their intracellular localization. The resulting new sub-5 nm silica-coated magnetic iron oxide fluorescent (sub-5 SIO-Fl) nanoparticles were tested in CaCo-2 cell line, a well characterized model of the intestinal epithelium, commonly used for biopharmaceutical evaluations as well in toxicity studies either as differentiated or undifferentiated cells. We studied sub-5 SIO-Fl nanoparticles cellular uptake and intracellular localization. Furthermore, we investigated if their uptake affected CaCo-2 cell morphology, growth, viability, cell cycle distribution, as well as transcriptional, translational and secretory activities, in a dose-dependent manner. To further shed light on their biocompatibility, the effect of the sub-5 SIO-Fl nanoparticles on CaCo-2 cell differentiation and pro-inflammatory response was analysed. Overall, these results showed the in vitro biocompatibility of the sub-5 SIO-Fl nanoparticles promising their safe employ for diagnostic and therapeutic biomedical applications. Since their magnetic nature, our nanoparticles could be easily in vivo directed toward the desired tissues/organs to shuttle drugs upon the application of an external static magnetic field. They could be used as efficient vehicles for drug/gene delivery for antiblastic therapies, enhancing the efficacy of treatments with reduced systemic toxicity. Moreover, these nanoparticles can maintain the ability to act as antennae in an external alternating magnetic field to convert electromagnetic energy into heat, to synergize the action of the shuttled drugs with hyperthermia.

Magnetic iron oxide nanoparticles (IONPs), for their intriguing properties, have attracted a great interest as they can be employed in many different biomedical applications. In this multidisciplinary study, we synthetized and characterized ultrafine 3 nm superparamagnetic water-dispersible nanoparticles. By a facile and inexpensive one-pot approach, nanoparticles were coated with a shell of silica and contemporarily functionalized with fluorescein isothiocyanate (FITC) dye. The obtained sub-5 nm silica-coated magnetic iron oxide fluorescent (sub-5 SIO-Fl) nanoparticles were assayed for cellular uptake, biocompatibility and cytotoxicity in a human colon cancer cellular model. By confocal microscopy analysis we demonstrated that nanoparticles as-synthesized are internalized and do not interfere with the CaCo-2 cell cytoskeletal organization nor with their cellular adhesion. We assessed that they do not exhibit cytotoxicity, providing evidence that they do not affect shape, proliferation, cellular viability, cell cycle distribution and progression. We further demonstrated at molecular level that these nanoparticles do not interfere with the expression of key differentiation markers and do not affect pro-inflammatory cytokines response in Caco-2 cells. Overall, these results showed the in vitro biocompatibility of the sub-5 SIO-Fl nanoparticles promising their safe employ for diagnostic and therapeutic biomedical applications.

Colloidal Quantum Dots (CQD), due to their extremely large optical absorption coefficient and tunability of the absorption bands, are very promising for the realization of photodetectors. PbS quantum dots, in particular, can be effectively employed as a material for near infrared photodetectors with sensitivity peaks ranging from 1 to 2 mu m. CQD photodetectors, nevertheless, present still many unsolved issues when it comes to fast detection and noise performance. Thanks to the recent advances in CQD material synthesis and treatment, photodetectors achieved unprecedented performance but the aforementioned issues could still not be fully addressed. Concerning photodetectors, however, material quality is only the starting point for the realization of performing devices: CQD technology came to the point where an engineering approach is needed in order to fully comprehend the behavior of the photodetectors, to define proper strategies for the enhancement of their performance and introduce them in practical applications. In this work we analyze the optical and electrical characteristics of PbS CQD near infrared photodetectors fabricated on SiO2 substrate and demonstrate how even a simple, fully passive readout circuit topology could be employed in order to obtain a dramatic enhancement of the characteristics of the devices.

Colloidal quantum dots have recently attracted lot of interest in the fabrication of optoelectronic devices due to their unique optical properties and their simple and low cost fabrication. PbS nanocrystals emerged as the most advanced colloidal material for near infrared photodetectors. In this work we report on the fabrication and characterization of PbS colloidal quantum dot photoconductors. In order to make devices suitable for the monolithic integration with silicon electronics, we propose a simple and low cost process for the fabrication of photodetectors and investigate their operation at very low voltage bias. Our photoconductors feature high responsivity and detectivity at 1.3 mu m and 1 V bias with maximum values of 30 A/W and 2.10(10) cmHz(1/2)W(-1), respectively. Detectivity close to 10(11) cmHz(1/2)W(-1) has been obtained resorting to bridge sensor readout.

Over the last decade, nanotechnology has become more relevant in medicine. Among magnetic nanomaterials the future of iron oxide nanoparticles (IONPs) for clinical applications relies on their biocompatibility in moderate doses as well as their ability to be produced in a wide range of sizes and shapes with biofunctionalization potential. Additionally, they show great promise to serve as a cell tracking system in cell-based therapies, and to generate local temperature increases in the magnetic thermotherapy of solid tumours. Thus, the study and development of novel magnetic nanoparticles for biomedical applications is one of the key topics in the field of nanotechnology. Extremely small-sized Fe3O4 superparamagnetic nanoparticles were prepared by coprecipitation, thinly coated with silica and conjugated with FITC, as molecular model specimen. Nanoparticles were characterized by dynamic light scattering (DSL), transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD) and surface functional groups and composition were analysed by infrared spectroscopy (FTIR). We assessed the biocompatibility of the magnetic nanoparticles carriers with biofunctional coating (FITC-conjugated) using a colon carcinoma cell line (CaCo-2) as human cellular model. Phase contrast, fluorescence and confocal microscopy analyses were performed to study nanoparticles up-take and internalization

The preparation of biorecognition layers on the surface of a sensing platform is a very crucial step for the development of sensitive and selective biosensor. The incredibly large specific surface area, the abundant surface functionalities and the high water solubility indicate graphene oxide (GO) sheets as ideal substrate for such application. The immobilization of aptamers as the recognition element on GO allows the formation of a nanocomplex, usable as biosensing platform in an aptasensors. In this work, we investigate the immobilization of the biotin-thrombin-aptamer on GO, exploiting the high affinity of avidin for biotin. Avidin was directly immobilized on GO without any chemical functionalization, following a simple incubation procedure, performed in PBS. The ability of Avidin-GO substrate to bind biotinylated aptamers could lead an oriented immobilization of the recognition element (i.e. aptamer), avoiding unwanted interaction between aptamer and GO and keeping intact the exposed binding sites for the thrombin assay. The immobilization was observed directly using atomic force microscopy (AFM) and the modification of the GO functional groups was verified by UV-vis and Fourier transform infrared (FT-IR) spectroscopy.

Graphene nanoribbons (GNRs), narrow stripes of graphene with a width typically smaller than 100 nm, have recently attracted extensive interests because of their unique structure-dependent electronic properties and promising applications in nanoelectronics and spintronics. We produced graphene nanoribbonds of high-quality, selected number of layers and low cost by means of a chemical method based on the growth of colloidal suspensions. Furthemore, by means of this process we obtained graphene nanoribbons with a low content of oxidized forms. This method could offer a low-cost route to large-scale graphene production. The structures were characterized by many AFM and Raman spectroscopy. The investigation of vibrational properties of graphene nanoribbons is of great interest for the physical understanding of these structures

An optical aptamer-based detection system label free appears as highly efficient device with enormous potential. Unfortunately such systems are still immature compared to immunoassays, reflecting the limited availability of aptamer types and the relatively poor knowledge of surface-immobilization technologies for aptamers [1]. We present the preparation of an aptamer terminated sensing surface, allowing a fast and cheap system for assay of analytes unlimited by size and tossicity. The designed platform is suitable for an aptamer-based microfluidic device, coupled with a Surface Enhanced Raman Spectroscopy (SERS). To accomplish this, a multi-step deposition sequence was performed: as a start, a mixed self assembled monolayer (SAM) containing a binary mixture of biotinylated alkylthiol (BAT) [2]. with the capacity to graft neutravidin proteins and diluent methyl-terminated alkylthiol, was prepared on a gold thin film. The chemical and electronic structure of the mixed SAMs was investigated by X-ray Photoelectron Spectroscopy and IRRAS (Infrared Spectroscopy in Reflection Mode) [3]. In a second step, the bioconjugation with an avidin-gold sol is performed. Monodispersed 5 nm gold particles were prepared in aqueous medium and covered with neutravidin, overcoming possible non-specific bindings, taking usually place at the isolectric point (~ 6) of neutravidin [4, 5]. The sample morphologies were observed by atom force microscopy (AFM), the size was determined by Dynamic Light Scattering and the concentration of gold species in the colloid was monitored by UV-vis spectra [6, 7]. In the ending step, a sensing aptamer (i. e. thrombin-binding aptamer) is bond to the surface through the avidin-biotin linkage. The resulting SERS changes involved was observed when the target molecule (i.e. thrombin) interacts with its own aptamer [8]. This aptamer terminated sensing surface is fitted for affinity based microfluidic devices, providing controlled fluid transport, rapid affinity assay and cost saving advantages over conventional methods for biological and medical applications. Through such design, the sensing surface overcomes the sandwich structure, formed between the immobilized aptamer, the protein target and a secondary aptamer bound to the Raman probe (i.e. gold nanoparticles ), usually realized in SERS aptasensors, limited by consuming and inconvenient handling step [9]. [1] Song S.; Wang L.; Li J.; Fan C.; Zhao J," Trends in Analytical Chemistry, 27, 2, 2008. [2] Ptrats-Alfonso E., Garcia-Martin F.,Bayo N., Cruz L.J., Pla-Roca M., Samitier J., Errachid A., Albericio F., Tetrahedron, 62, 6876-6881, 2006 [3] Nelson K.E., Gamble L., et al., Langmuir, 17, 2807-2816, 2001. [4] Grabar, K.C et al., Anal. Chem., 67, 735-743, 1995. [5] Morris R.E. and Saelinger C.B.., J.Histochemistry and Cytochemistry, 32, 124-128, 1984 [6] Kimling J. et al., J.Phys.Chem B 110, 15700-15707, 2006 [7] Ji X. et al., J.Am.Chem.Soc. 129, 13939-13948, 2007 [8] Nie S.; and Emory S. R., Science 275, 1102, 1997. [9]. Sassolas A, Blum L. J., Leca-Bouvier B. D., Biosens Bioelectron., on line, 2011

An optical aptamer-based detection system label free appears as highly efficient device with enormous potential. Unfortunately such systems are still immature compared to immunoassays, reflecting the limited availability of aptamer types and the relatively poor knowledge of surface-immobilization technologies for aptamers [1]. We present the preparation of an aptamer terminated sensing surface, allowing a fast and cheap system for assay of analytes unlimited by size and tossicity. The designed platform is suitable for an aptamer-based microfluidic device, coupled with a Surface Enhanced Raman Spectroscopy (SERS). To accomplish this, a multi-step deposition sequence was performed: as a start, a mixed self assembled monolayer (SAM) containing a binary mixture of biotinylated alkylthiol (BAT) [2]. with the capacity to graft neutravidin proteins and diluent methyl-terminated alkylthiol, was prepared on a gold thin film. The chemical and electronic structure of the mixed SAMs was investigated by X-ray Photoelectron Spectroscopy and IRRAS (Infrared Spectroscopy in Reflection Mode) [3]. In a second step, the bioconjugation with an avidin-gold sol is performed. Monodispersed 5 nm gold particles were prepared in aqueous medium and covered with neutravidin, overcoming possible non-specific bindings, taking usually place at the isolectric point (~ 6) of neutravidin [4, 5]. The sample morphologies were observed by atom force microscopy (AFM), the size was determined by Dynamic Light Scattering and the concentration of gold species in the colloid was monitored by UV-vis spectra [6, 7]. In the ending step, a sensing aptamer (i. e. thrombin-binding aptamer) is bond to the surface through the avidin-biotin linkage. The resulting SERS changes involved was observed when the target molecule (i.e. thrombin) interacts with its own aptamer [8]. This aptamer terminated sensing surface is fitted for affinity based microfluidic devices, providing controlled fluid transport, rapid affinity assay and cost saving advantages over conventional methods for biological and medical applications. Through such design, the sensing surface overcomes the sandwich structure, formed between the immobilized aptamer, the protein target and a secondary aptamer bound to the Raman probe (i.e. gold nanoparticles ), usually realized in SERS aptasensors, limited by consuming and inconvenient handling step [9]. [1] Song S.; Wang L.; Li J.; Fan C.; Zhao J," Trends in Analytical Chemistry, 27, 2, 2008. [2] Ptrats-Alfonso E., Garcia-Martin F.,Bayo N., Cruz L.J., Pla-Roca M., Samitier J., Errachid A., Albericio F., Tetrahedron, 62, 6876-6881, 2006 [3] Nelson K.E., Gamble L., et al., Langmuir, 17, 2807-2816, 2001. [4] Grabar, K.C et al., Anal. Chem., 67, 735-743, 1995. [5] Morris R.E. and Saelinger C.B.., J.Histochemistry and Cytochemistry, 32, 124-128, 1984 [6] Kimling J. et al., J.Phys.Chem B 110, 15700-15707, 2006 [7] Ji X. et al., J.Am.Chem.Soc. 129, 13939-13948, 2007 [8] Nie S.; and Emory S. R., Science 275, 1102, 1997. [9]. Sassolas A, Blum L. J., Leca-Bouvier B. D., Biosens Bioelectron., on line, 2011

Aptamers, specific nucleic acid selected from random sequence pools, are a valid alternative to antibodies or other biomimetic receptors. Aptamer-based biosystems are still immature compared to immunoassays, which reflects the limited availability of aptamer types and for this purpose an optical aptamer-based detection systems label free appear as highly efficient devices with enormous potential. [Ellington, A.D., Szostak, J.W., 1990. Nature 346,818-822; Song S., Wanga L., Lia J., Fana C., Zhaob J., 2008 TrAC 27(2), 108-117] We approach the development of an affinity based detection system for analytes unlimited by size and tossicity, designing a nanoaptasensor sensing surface for microfluidic device, coupled with Surface Enhanced Raman Spectroscopy (SERS). Among the optical detection methods, SERS distinguishes itself with several advantages: the spectrum change brought by a single molecules, is induced by the specific interaction between aptamers and their own proteins and the spectral probe specificity is excellent in comparison to the fluorescence methods. The thrombin aptamer is the first example of ssDNA oligonucleotides that bind a target protein with unknown specificity for nucleic acids. [Bock, L.C., et al., 1992. Nature 355, 564-566] A Thrombin SERS aptasensor is usually realized by a sandwich structure, formed between the immobilized aptamer, the protein target and a secondary aptamer bound to a Raman probe (i.e. gold nanoparticles ), which requires a consuming and inconvenient handling step. [Sassolas A, Blum L. J., Leca-Bouvier B. D. 2011 Biosens Bioelectron., on line] In attempt to over come this drawback we report the preparation of a aptamer terminated sensing surface, allowing a faster and cheaper system and suitable for an analytical label free measurements, in order to perform a direct analisys of biological samples. We develop a multi-step depositional sequence: firstly was prepared a mixed self assembled monolayer (SAM) on a gold thin film, containing a binary mixture of biotinylated alkylthiol (BAT) with the capacity to graft neutravidin proteins and diluent methyl-terminated alkylthiol. The composition depth profile of the mixed SAMs was examined by angle-resolved XPS. Insight in to the order of the SAM system was provided by NEXAFS characterization [Nelson K.E., Gamble L., et al. 2001, Langmuir, 17, 2807-2816]. BAT was produced by a solid-phase synthesis, based on a resin, which protects the thiol group and prevents the formation of non-desired compounds [Prats-Alfonso E. et al. 2006 Tetrahedron 62, 6876-6881]. In a second step, the bioconjugation with an avidin-gold sol is performed. Monodispersed 5 nm gold particles were prepared in aqueous medium and covered with neutravidin, overcoming possible non-specific bindings, which are usually attribuited to the isolectric point (~ 6) of neutravidin [Grabar, K.C et al. 1995 Anal. Chem. 67, 735-743; Morris R.E. and Saelinger C.B. 1984 The journal of Histochemistry and Cytochemistry 32, 124-128]. Gold colloid was prepared by reducing tetrachloroauric(III) acid with sodium citrate controlling growth kinetics and temporal size/shape evolution of gold nanocrystal. The citrate plays a dual role as reducing agent and protection capping group and temperature and pH values of the citrate reaction drastically affect the size and quality of the particles. The morphologies was observed by atom force microscopy (AFM) and the concentration of gold species in the colloid was monitored by UV-vis spectra.[Kimling J. et al.2006 J.Phys.Chem B 110, 15700-15707; Ji X. et al. 2007 J.Am.Chem.Soc. 129, 13939-13948] In the ending step, the Aptamer is bond to the surface thought the avidin-biotin linkage. In this strategy aptamer against thrombin [5'GGT TGG TGT GGT TGG T(15)3'Biotin], marked by a guanine quadruplex (G-quadruplex), is used. The resulting SERS changes involved was observed when the target molecule (Thrombin) interacts with its own aptamer [Nie S.; and Emory S. R. 1997 Science 275, 1102].

This paper reports on the low temperature synthesis of L10 iron–platinum (FePt) particles within multiwall carbon nanotubes using a novel wet chemical method that allows the filling of the nanotube cavity keeping clean its external wall. In the proposed procedure, nanotubes are filled with a precursor salt of hexaaquairon(II) hexachloroplatinate, ([Fe(H2O)6][PtCl6]) and nanoparticles of the magnetically hard phase are directly obtained by heating at 400 °C in a reductive atmosphere. The advantage of such a precursor, allowing one to obtain at low temperature the L10 phase without passing through the soft fcc phase, is due to its structure, where the Fe and Pt atoms are arranged in alternating planes, as in the fct FePt structure. Morphological, structural and magnetic properties of the filled nanotubes have been investigated by transmission electron microscopy, x-ray diffraction and magnetization measurements. The results show the coexistence of nanoparticles in the superparamagnetic and blocked state, depending on the temperature, due to the particle size distribution.