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Optical probes operating in the second near-infrared window (NIR-II, 1,000-1,700 nm), where tissues are highly transparent, have expanded the applicability of fluorescence in the biomedical field. NIR-II fluorescence enables deep-tissue imaging with micrometric resolution in animal models, but is limited by the low brightness of NIR-II probes, which prevents imaging at low excitation intensities and fluorophore concentrations. Here, we present a new generation of probes (Ag 2 S superdots) derived from chemically synthesized Ag 2 S dots, on which a protective shell is grown by femtosecond laser irradiation. This shell reduces the structural defects, causing an 80-fold enhancement of the quantum yield. PEGylated Ag 2 S superdots enable deep-tissue in vivo imaging at low excitation intensities (<10 mW cm −2 ) and doses (<0.5 mg kg −1 ), emerging as unrivaled contrast agents for NIR-II preclinical bioimaging. These results establish an approach for developing superbright NIR-II contrast agents based on the synergy between chemical synthesis and ultrafast laser processing. Deep tissue imaging has been limited by the low brightness of probes emitting in the second near-infrared window. Here, the authors use femtosecond laser irradiation to grow a protective shell on Ag 2 S nanoparticles, achieving 80-fold quantum yield enhancement and imaging with low excitation intensities.

The potential of a new poly(magnesium acrylate) hydrogel (PAMgA) as a pharmaceutical excipient for the elaboration of matrix tablets for the extended release of highly hydrophilic drugs was evaluated. The polymer was synthetized with two different crosslinking degrees that were characterized by FTIR and DSC. Their acute oral toxicity was determined in a mouse model, showing no toxicity at doses up to 10 g/kg. Matrix tablets were prepared using metformin hydrochloride as a model drug and the mechanisms involved in drug release (swelling and/or erosion) were investigated using biorrelevant media. This new hydrogel effectively controlled the release of small and highly hydrophilic molecules as metformin, when formulated in matrix tablets for oral administration. The rate of metformin release from PAMgA matrices was mainly controlled by its diffusion through the gel layer (Fickian diffusion). The swelling capacity and the erosion of the matrix tablets influenced the metformin release rate, that was slower at pH 6.8, where polymer swelling is more intensive, than in gastric medium, where matrix erosion is slightly more rapid. The crosslinking degree of the polymer significantly influenced its swelling capacity in acid pH, where swelling is moderate, but not in intestinal fluid, where swelling is more intense.

Brushite cement has advantages such as fast setting, high reactivity and good injectability over apatitic cements. To induce the bioactivity of brushite cements, the goal was to convert it into a bone-like low crystalline carbonate apatite. To achieve this induced transformation, potassium and magnesium were used as dopants which were claimed to be effective in the literature. The cements were immersed for 2 periods of time: 1 day and 6 weeks in Tas-Simulated-Body-Fluid (Tas-SBF) due to its excellent biomimetic properties with its adjusted HCO3- and Cl- ionic rates according to human-blood-plasma. 5% of potassium (to calcium sites) seemed to be more effective over magnesium modification. The aim of this study is to define an optimal composition in terms of transforming brushite into apatite.

We have developed a new biomaterial based on calcium silicate and calcium phosphate whose structure and properties depend on the silicon content. The cement was prepared using as a solid phase a mixture of silicon-doped β-tricalcium phosphate (Si-β-TCP) and monocalcium phosphate monohydrated (MCPM) and as a liquid phase an aqueous solution. The main phases of silicon-doped calcium phosphate cements (Si-CPCs) were brushite , silicarnotite , and hydroxyapatite (HA); it is worth noting the peaks in the cements prepared with 80 wt.% Si-β-TCP of larnite , wallastonite , and calcium carbonate. To increasing silicon content, the Si-CPCs experienced great changes in their morphology forming scaffolds of pore diameters of 0.05, 0.02, and 0.04 µm for 40, 60, and 80 wt.% of Si-CPCs respectively, indicating that the tortuosity and mechanical properties of the cement matrix change with the amount of Si added in Si-β-TCPs. These changes in Si-CPC porosity could help to improve the properties of biomaterials for bone regeneration with a simple method in a cost-effective way.

The incorporation of strontium chloride to brushite cement was successful to introduce strontium ions within the lattice of brushite crystals. The effect of strontium ions on brushite cement properties was concentration dependent; such that, the addition of 5% and 10% (w/w) SrCl2 significantly increased the cement FST and the addition of 10% SrCl2 decreased the cement tensile strength. Further, cement weight loss was shown to be increased by cement modification with SrCl2. The combination of ionic substitution and the degradability of brushite cements would constitute a system for the local delivery of strontium ions in the treatment of osteoporosis.

In this paper, we report on the preparation of a novel poly(magnesium acrylate) (PAMGA) hydrogel by free radical homopolymerization of magnesium acrylate in aqueous solution. The effect of the concentration of monomer and initiator on the rheological and swelling properties of PAMGA hydrogels was studied. In the equilibrium of swelling, these hydrogels show a phase transition characterized by the transformation from a transparent to an opaque‐milky structure associated with a change in the viscoelastic properties of the hydrogels. The influence of the concentrations of monomer and initiator on the phase transition has been studied and the results show that the temperature of the phase transition increases with both the concentration of monomer and the concentration of initiator, the effect of the initiator being more pronounced. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

The controlled synthesis of gold or silver nanostructures has attracted considerable attention because of their widespread use in catalysis, photonics, electronics, optoelectronics, biological labeling, imaging, sensing, and surface-enhanced Raman scattering (SERS) (Chen et al. 2005b; Maier et al. 2001; Taton et al. 2000; Tkachenko et al. 2003; Zhang et al. 2005). Gold and silver nanostructures can be also encapsulated into microgels to produce hybrid materials with thermoresponsive properties or magnetic and optical properties for SERS ultradetection (ContrerasCaceres et al. 2008, 2011). Besides size, shape is an important factor that controls the electronic and optical properties of metal nanoparticles. In particular, the morphological control of asymmetric Au or Ag nanostructures allows tuning the localized surface plasmon resonance (SPR) in the visible and near-infrared regions (Hu et al.

F\"orster resonant energy transfer (FRET) with upconverting nanoparticles (UCNPs) as donors and quantum dots (QDs) as acceptors has been regarded as a promising tool for biosensing applications. In this work, we use time-resolved fluorescence spectroscopy to analyze the UCNP-to-QD FRET and we focus on the most relevant parameter of the FRET phenomenon, UCNP-QD distance. This distance is controlled by a nanometric silica shell around the UCNP surface. We theoretically reproduce the experimental results applying FRET theory to the distribution of emitting erbium ions in the UCNP. This simple model allows us to estimate the contribution of every erbium ion to the final FRET response and to explore different strategies to improve FRET efficiency.

In many of these works, the thermosensitive microgels are combined with inorganic components such as quantum dots (Jaczewski et al. 2009), silver (Xu et al. 2006), gold (Kawano et al. 2009) or magnetic nanoparticles (Luo et al. 2010) to yield nanostructured and multifunctional hybrid material. The combination between the organic and the inorganic components establishes a symbiotic relation in which the microgels give colloidal stability as well as stimuli-responsive features, while the inorganic counterparts provide quantum properties such as photoluminescence (Agrawal et al. 2008; Bai et al. 2010), surface plasmon resonance (Karg et al. 2009), or magnetism (Schachschal et al. 2010).