Strontium-rich injectable hybrid system for bone regeneration.

Current challenges in the development of scaffolds for bone regeneration include the engineering of materials that can withstand normal dynamic physiological mechanical stresses exerted on the bone and provide a matrix capable of supporting cell migration and tissue ingrowth. The objective of the present work was to develop and characterize a hybrid polymer­ceramic injectable system that consists of an alginate matrix crosslinked in situ in the presence of strontium(Sr), incorporating a ceramic reinforcement in the form of Sr-rich microspheres. The incorporation of Sr in the microspheres and in the vehicle relies on the growing evidence that Sr has beneficial effects in bone remodeling and in the treatment of osteopenic disorders and osteoporosis. Sr-rich porous hydroxyapatite microspheres with a uniform size and a mean diameter of 555 µm were prepared, and their compression strength and friability tested. A 3.5% (w/v) ultrapure sodium alginate solution was used as the vehicle and its in situ gelation was promoted by the addition of calcium (Ca) or Sr carbonate and Glucone-δ-lactone. Gelation times varied with temperature and crosslinking agent, being slower for Sr than for Ca, but adequate for injection in both cases. Injectability was evaluated using a device employed in vertebroplasty surgical procedures, coupled to a texture analyzer in compression mode. Compositions with 35%w of microspheres presented the best compromise between injectability and compression strength of the system, the force required to extrude it being lower than 100 N.Micro CT analysis revealed a homogeneous distribution of the microspheres inside the vehicle, and a mean inter-microspheres space of 220 µm. DMA results showed that elastic behavior of the hybrid is over the viscous one and that the higher storage modulus was obtained for the 3.5%Alg­35%Sr-HAp-Sr formulation.

Carbon dots on based folic acid coated with PAMAM dendrimer as platform for Pt(IV) detection.

Carbon quantum dots (CQDs) coated with poly(amidoamine) (PAMAM-NH2) dendrimer are prepared from folic acid and phosphoric acid under a hydrothermal procedure. The obtained nanoparticles are successfully used as fluorescent sensor for Pt(IV) (in the form of chloroplatinate ion). CQDs possess many attractive features including uniform dispersion with average size about 13nm for unmodified particles and, ∼30nm when they are coated with PAMAM-NH2 dendrimer. The synthesized nanoparticles have been characterized by elemental analysis, attenuated total reflectance (ATR), X-ray photoelectron (XPS) and Raman spectroscopies, transmission electron microscopy (TEM), dynamic light scattering (DLS), and steady-state and life-time fluorescence. CQDs are used as fluorescent sensor of Pt(IV) ion in aqueous media showing linear quenching effect of their fluorescence. The results obtained demonstrated a limit of detection of 657nM with an accuracy of the method of 0.13% (as RSD, n=10) and sensitivity of 78nM. Moreover, with the presence of other interference species, good results are obtained when applied in real samples from platinum nanoparticles synthesis. The dissolved platinum ions can be quantified in the range 6-96µM with an accuracy of 2.5%.

ZnS:Mn nanoparticles functionalized by PAMAM-OH dendrimer based fluorescence ratiometric probe for cadmium.

We report a nanocomposite of ZnS:Mn quantum dots and a third generation PAMAM-OH dendrimer (ZnS:Mn@PAMAM-OH(G=3)) which was rationalized to be used as ratiometric nanosensor for Cd(2+) in aqueous solution. The nanoparticles exhibited a bright yellow-orange emission with peaks at 448 and 595 nm. The structure of ZnS:Mn was not changed after coupling with PAMAM-OH, which was evidenced by the analysis of the emission spectra of the compounds. The results confirm that the prepared fluorescence nanoparticles could selectively detect Cd(2+) in aqueous solution with a limit of detection of 24.34 µM and RSD 4.07%, obtained by using the ratio I448/I595. The method was applied to different water samples.

Improving patient care: alternative rubber dam isolation methods / Melhorando o cuidado ao paciente: métodos alternativos de isolamento absoluto

Adhesive techniques are more sensitive than conventional techniques and it is mandatory to isolate the operatory . To accomplish this goal, rubber dam isolation is the gold standard procedure. In root canal treatment, use of a rubber dam is found to be the standard of care, however, it is usually abandoned by professionals as time progresses from graduation to professional life, since the prevalence of rubber dam use is found to be low in many studies. To increase the use of rubber dams, adaptations of traditional techniques have been suggested. One possible way of reducing gingival trauma and pain promoted by isolation clamps during rubber dam usage would be the application of a thin layer of a soft material between the clamp and the tooth/gingival tissue. Objective: The purpose of the present work is to present alternative methods of rubber dam isolation, thus improving patient care. Description: Two methods are described: 1- Dam Coverage Method- Clamping the rubber dam over the tooth (putting the clamp over the dam and the teeth at the same time, without including the clamped tooth in the operatory ); 2- Silicone Coverage Method: Inter positioning of a heavy (high viscosity) silicone impression material between the tooth and the clamp. Conclusions: The current authors purposed two simple methods for absolute operatory isolation using a rubber dam. These methods reduce sensitivity, provide little or no gingival trauma and better comfort to the patient during rubber dam isolation as well as in the postoperative period, thus improving patient care.

Técnicas adesivas são mais sensíveis do que as convencionais, neste contexto, isolar o campo operatório é fundamental e o isolamento absoluto é o procedimento padrão-ouro. No tratamento endodôntico, o uso de um dique de borracha é reconhecido como padrão em cuidado de atendimento, no entanto, este é geralmente abandonado com o passar do tempo. Para aumentar a utilização de diques de borracha, adaptações das técnicas tradicionais têm sido sugeridas. Uma maneira possível de reduzir o trauma e a dor gengivais promovidos por grampos de isolamento seria a aplicação de uma fina camada de um material macio entre o grampo e o tecido dentário / gengival. Objetivo: O objetivo do presente trabalho é apresentar métodos alternativos de isolamento absoluto, melhorando assim o atendimento ao paciente. Descrição: Dois métodos são descritos: 1 - Cobertura com o Dique, que consiste na apreensão do dique de borracha sobre o dente (colocando o grampo sobre o dique de borracha e os dentes, ao mesmo tempo, sem a inclusão do dente no campo operatório), 2 - Cobertura com Silicona: consiste no posicionamento da silicona de condensação ou adição do tipo massa densa (alta viscosidade) entre o dente e o grampo. Conclusões: Os autores apresentaram dois métodos simples para o isolamento absoluto do campo operatório usando um dique de borracha que podem reduzir a sensibilidade e minimizar ou até mesmo evitar o trauma gengival provocado pelos grampos de isolamento, oferecendo assim conforto para o paciente durante e após o procedimento, melhorando a qualidade do atendimento prestado ao mesmo.

Fluorescent properties of a hybrid cadmium sulfide-dendrimer nanocomposite and its quenching with nitromethane.

A fluorescent hybrid cadmium sulphide quantum dots (QDs) dendrimer nanocomposite (DAB-CdS) synthesised in water and stable in aqueous solution is described. The dendrimer, DAB-G5 dendrimer (polypropylenimine tetrahexacontaamine) generation 5, a diaminobutene core with 64 amine terminal primary groups. The maximum of the excitation and emission spectra, Stokes' shift and the emission full width of half maximum of this nanocomposite are, respectively: 351, 535, 204 and 212 nm. The fluorescence time decay was complex and a four component decay time model originated a good fit (chi = 1.20) with the following lifetimes: tau (1) = 657 ps; tau (2) = 10.0 ns; tau (3) = 59.42 ns; and tau (4) = 265 ns. The fluorescence intensity of the nanocomposite is markedly quenched by the presence of nitromethane with a dynamic Stern-Volmer constant of 25 M(-1). The quenching profiles show that about 81% of the CdS QDs are located in the external layer of the dendrimer accessible to the quencher. PARAFAC analysis of the excitation emission matrices (EEM) acquired as function of the nitromethane concentration showed a trilinear data structure with only one linearly independent component describing the quenching which allows robust estimation of the excitation and emission spectra and of the quenching profiles. This water soluble and fluorescent nanocomposite shows a set of favourable properties to its use in sensor applications.

Mercury(II) sensing based on the quenching of fluorescence of CdS-dendrimer nanocomposites.

A chemical sensor for mercury(II) (Hg(II)) was developed based on the quenching of the fluorescence of cadmium sulfide (CdS) quantum dots (QDs) coated with polypropylenimine tetrahexacontaamine dendrimer (DAB) generation 5, CdS-DAB nanocomposites. The synthesis and characterization of CdS-DAB nanocomposites by means of EDXA, SEM and steady state luminescence is described. Macroscopic spherical structures are observed by electronic microscopy and the wavelength for the maximum fluorescence emission occurs at 535 nm (excitation at 351 nm). Stern-Volmer plots show a linear response in the range of 1 x 10(-6) to 1 x 10(-5) M with a quenching constant (K(sv)) of 1.5 x 10(5) M(-1). A parallel factor (PARAFAC) analysis model confirmed that Hg(II) alone provokes quenching of the fluorescence. Cu(II) and Pb(II) also quench the fluorescence of CdS-DAB nanocomposites, with a K(sv) = 1.9 x 10(5) M(-1) and K(sv) = 2.2 x 10(4) M(-1), respectively, and Cd(II), Zn(II), Co(II) and Ni(II) have no effect. Ionic strength, in the range from 1.25 x 10(-3) up to 2 M, provokes a shift in the wavelength of the maximum of the emission spectra, from 482 to 677 nm.