Uniform, Binary Functionalization of a Metal-Organic Framework Material.

General routes to confined spaces of well-defined chemical composition and complex three-dimensional structure have long been sought by materials chemists. Here, we introduce metal-organic framework (MOF) materials as an ideal scaffold upon which such organized complexity can be built. Employing an orthogonal coordination strategy, we constructed a large-pore MOF material with two different modifiable linkers in well-defined positions relative to each other. The independent and quantitative covalent grafting of two distinct chemical groups onto these differently reactive linkers yielded a uniformly bifunctionalized MOF material. Not only does this methodology offer an efficient route via which the properties of well-defined microporous materials can be fine-tuned, but it also creates a solid-state platform for synthetically accessing constructs that better emulate the well-ordered intricacy of biological structures.

Manganese Doped Hydroxyapatite Nanoparticles Based Enzyme-Less Electrochemical Sensor for Detecting Hydroquinone.

Manganese (Mn) doped hydroxyapatite (HA) nanoparticles were synthesized by a simple microwave irradiation method and characterized using XRD, SEM, micro-Raman, FTIR, XPS and vibrating sample magnetometer (VSM) methods. The as prepared 3 M% Mn doped HA (3 M% Mn-HA) nanoparticles modified glassy carbon electrode (GCE) showed an excellent electrocatalytic activity towards the oxidation of hydroquinone (HQ). The electrochemical studies demonstrated that the 3 M% Mn-HA nanoparticles modified GCE detects HQ linearly over a wide concentration range of 1.0×10-8 to 1.6×10-4 M with the lowest detection limit of 11 nM at neutral pH (7.0) in PBS. Furthermore, Mn-HA modified GCE exhibited an excellent stability, reproducibility and anti-interference ability against a number of potential electroactive species and metal ions and proved to be useful for the estimation of the HQ in tap water and industry waste water with satisfactory recovery.

Effectiveness of Hindfoot Arthrodesis by Stable Internal Fixation in Various Eichenholtz Stages of Neuropathic Ankle Arthropathy.

The optimal time to treat neuropathic (Charcot) arthropathy of the ankle and peritalar joint is controversial because of the various treatment options available and the variable results reported in published studies. We sought to determine the outcome of hind foot arthrodesis with stable internal fixation in patients with different Eichenholtz stages of arthropathy. We prospectively studied patients with substantial disabilities caused by neuropathic arthropathy in deformed, unstable ankle and peritalar joints, with or without ulcerations, who had undergone treatment from July 2007 to December 2012. All patients underwent ankle arthrodesis, autologous iliac crest bone grafting, and subtalar joint arthrodesis, with or without talonavicular joint arthrodesis, fixed internally with an intramedullary hindfoot nail, with or without an additional plate or cancellous screws. Of the 33 enrolled patients, 9 (27.3%) had stage I, 13 (39.4%) had stage II, and 11 (33.3%) had stage III Charcot arthropathy. The cause of arthropathy was diabetes mellitus in 25 (75.8%) patients. The duration of symptoms ranged from 1 to 120 (median 7) months. The mean follow-up period was 40 (range 12 to 76) months and did not differ markedly among the groups. The hindfoot scores, rate of salvage or amputation, or complication rates did not differ significantly across Eichenholtz stage. For the patients with stage I, II, and III, the preoperative hindfoot score was 50, 49, and 48, respectively (p = .9). The corresponding postoperative scores were 68, 68, and 70 (p = .5). We found no evidence that the effectiveness of hindfoot arthrodesis by stable fixation varied across the Eichenholtz stage of Charcot arthropathy involving ankle and peritalar joint. Furthermore, we found that stable internal fixation and bone grafting using a hindfoot nail results in an 84.84% union rate and salvages the unstable and disabled foot in 90.9% of patients with ankle and peritalar Charcot arthropathy.

Electrochemical Sensor Based on Fe Doped Hydroxyapatite-Carbon Nanotubes Composite for L-Dopa Detection in the Presence of Uric Acid.

A novel amperometric sensor based on iron doped hydroxyapatite (Fe-HA) and multiwalled carbon nanotubes (CNT) composite immobilized on a glassy carbon electrode (GCE) has been fabricated. The hybrid composite made of Fe-HA nanoparticles and CNT promotes electron transfer kinetics between the analyte levodopa (L-dopa) and the modified GC electrode. Under optimum conditions, the fabricated sensor gave a linear response range of 1.0 x 10(-7)-1.1 x 10(-6) M with the detection limit as low as 62 nM. The Fe-HA/CNT modified electrode showed good selectivity towards the determination of L-dopa in the presence of ascorbic acid (AA), uric acid (UA) and other common interferents. The sensor displays a high sensitivity, good reproducibility and long-term stability and it was successfully applied for the detection of L-dopa in pharmaceutical and medicinal plant samples.

Acoustic impedance-based size-independent isolation of circulating tumour cells from blood using acoustophoresis.

Label-free isolation of CTCs from blood is critical for the development of diagnostic and prognostic tools for cancer. Here, we report a label-free method based on acoustic impedance contrast for the isolation of CTCs from peripheral blood mononuclear cells (PBMCs) in a microchannel using acoustophoresis. We describe a method in which the acoustophoretic migration of PBMCs is arrested by matching their acoustic impedance with that of the sample medium, and CTCs that have different acoustic impedance compared to PBMCs migrate toward the pressure node or antinode and thus become isolated. We show that acoustic streaming which can adversely affect the CTC isolation is suppressed owing to the inhomogeneous liquid flow configuration. We establish a method for isolation of CTCs that have higher or lower acoustic impedance compared to PBMCs by controlling the acoustic impedance contrast of the liquids across the channel. Applying this method, we demonstrate label-free isolation of HeLa and MDA-MB-231 cells from PBMCs (collected from 2.0 mL of blood) within one hour yielding a recovery of >86% and >50-fold enrichment. Combined impedance and size-based sorting is proposed as a promising tool for the effective isolation of CTCs from blood.

Development of electrochemical folic acid sensor based on hydroxyapatite nanoparticles.

We report the synthesis of hydroxyapatite (HA) nanoparticles (NPs) by a simple microwave irradiation method and its application as sensing element for the precise determination of folic acid (FA) by electrochemical method. The structure and composition of the HA NPs characterized using XRD, FTIR, Raman and XPS. SEM and EDX studies confirmed the formation of elongated spherical shaped HA NPs with an average particle size of about 34 nm. The HA NPs thin film on glassy carbon electrode (GCE) were deposited by drop casting method. Electrocatalytic behavior of FA in the physiological pH 7.0 was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. The fabricated HA/GCE exhibited a linear calibration plot over a wide FA concentration ranging from 1.0×10(-7) to 3.5×10(-4) M with the detection limit of 75 nM. In addition, the HA NPs modified GCE showed good selectivity toward the determination of FA even in the presence of a 100-fold excess of ascorbic acid (AA) and 1000-fold excess of other common interferents. The fabricated biosensor exhibits good sensitivity and stability, and was successfully applied for the determination of FA in pharmaceutical samples.

EDTA assisted synthesis of hydroxyapatite nanoparticles for electrochemical sensing of uric acid.

Hydroxyapatite nanoparticles have been synthesized using EDTA as organic modifier by a simple microwave irradiation method and its application for the selective determination of uric acid (UA) has been demonstrated. Electrochemical behavior of uric acid at HA nanoparticle modified glassy carbon electrode (E-HA/GCE) has been investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), linear sweep voltammetry (LSV) and amperometry. The E-HA modified electrode exhibits efficient electrochemical activity towards uric acid sensing without requiring enzyme or electron mediator. Amperometry studies revealed that the fabricated electrode has excellent sensitivity for uric acid with the lowest detection limit of 142 nM over a wide concentration range from 1 × 10(-7) to 3 × 10(-5)M. Moreover, the studied E-HA modified GC electrode exhibits a good reproducibility and long-term stability and an admirable selectivity towards the determination of UA even in the presence of potential interferents. The analytical performance of this sensor was evaluated for the detection of uric acid in human urine and blood serum samples.

Development of amperometric L-tyrosine sensor based on Fe-doped hydroxyapatite nanoparticles.

A novel biosensor based on Fe-doped hydroxyapatite (Fe-HA) nanoparticles and tyrosinase has been developed for the detection of L-tyrosine. Nanostructured Fe-HA was synthesized by a simple microwave irradiation method, and its phase formation, morphology and magnetic property were examined by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). Electrochemical performance of the nano Fe-HA/tyrosinase modified glassy carbon electrode (GCE) for detection of L-tyrosine was investigated by cyclic voltammetry (CV) and amperometric methods. The fabricated biosensor exhibited a linear response to L-tyrosine over a wide concentration range of 1.0×10(-7) to 1.0×10(-5) M with a detection limit of 245 nM at pH 7.0. In addition, the fabricated sensor showed an excellent selectivity, good reproducibility, long-term stability and anti-interference towards the determination of L-tyrosine.

Effect of trivalent metal ion impurities (Al3+, Cr3+ and Fe3+) on the growth, structural and physical properties of potassium acid phthalate (KAP) crystals.

Trivalent metal ion (Al, Cr, Fe) doped potassium hydrogen phthalate (KAP) crystals have been grown from aqueous solution at room temperature. Powder XRD and ICP-OES studies confirmed the metal ion doping into KAP crystals. The presence of functional groups in the crystal has been observed by FTIR analysis. Optical transmission studies were carried out by allowing the UV-NIR ray of wavelength between 190 and 1000 nm to pass through the (010) face of the grown KAP crystals. Dielectric constant value of Fe-doped KAP at 100 Hz was found to be significantly higher than that of undoped and Cr and Al-doped KAP. TG-DTA studies show the decomposition temperatures to be 255, 270, 258 and 287 °C for pure, Al(3+), Cr(3+) and Fe(3+) doped KAP crystals respectively. Microhardness studies reveal that the Cr(3+) and Fe(3+) doped crystals have higher hardness values than that of undoped and Al-doped KAP. The grown crystals were also subjected to second harmonic generation (SHG) efficiency tests.

Effect of divalent metal ion impurities (Ba²âº, Ca²âº and Mg²âº) on the growth, structural and physical properties of KAP crystals.

Single crystals of potassium hydrogen phthalate (KAP), a semi-organic compound, have been grown by slow evaporation method at room temperature from aqueous solution in the presence of divalent metal ionic impurities Ba(2+), Ca(2+) and Mg(2+). Elemental analysis by inductively coupled plasma optical emission spectroscopy (ICP-OES) proves the incorporation of these impurities into the grown crystals. Powder X-ray diffraction studies confirmed the phase formation and metal ions doping into KAP crystals. Thermogravimetric-differential thermal analysis (TG-DTA) shows the onset decomposition temperatures to be 255, 238, 251 and 250°C for pure, Ba(2+), Ca(2+) and Mg(2+) doped KAP crystals respectively. Microhardness studies revealed that all the three doped crystals have improved hardness values than that of undoped KAP crystal. Ca-KAP crystal exhibited the highest second harmonic generation (SHG) conversion efficiency of 16 mV with the output power of nearly half of the standard potassium dihydrogen phosphate (KDP) crystal. The grown crystals were also subjected to Fourier transform infrared (FTIR) spectroscopy, ultra violet-visible-near infrared (UV-NIR) spectroscopy studies and dielectric studies. Among the three investigated metal ion impurities, Ca(2+) ion seem to have positive influence on the growth, mechanical, thermal, dielectric and SHG characteristics of KAP which makes it suitable for applications.

Effect of amino acid additives on the growth and physical properties of potassium acid phthalate (KAP) crystals.

Single crystals of potassium acid phthalate (KAP) have been grown from aqueous solution by slow evaporation technique by adding l-alanine (LA), glycine (Gly) and l-tyrosine (LT) as additives. Powder X-ray diffraction studies confirmed the phase formation and amino acids doping into KAP crystals. The optical absorption studies reveal that the LA doped crystals possess less absorption of visible ray than the pristine, Gly and LT doped KAP crystals. Optical transmission is found to be low in LT doped KAP than in all the other crystals. TG-DTA studies show the decomposition temperatures to be 255 °C, 232 °C, 258 °C and 264 °C for pure, LA, Gly and LT doped KAP crystals respectively. SHG efficiency of LA doped KAP crystal was found to be 1.1 times (31 mV for KDP and 34 mV for LA doped KAP) that of potassium dihydrogen phosphate (KDP) crystal. This is much higher when compared to that of undoped KAP crystal (12mV). The grown crystals were also subjected to FTIR, microhardness and dielectric studies.

Calibration of force extension and force degradation characteristics of orthodontic latex elastics.

The force-extension characteristics of orthodontic elastics made of natural rubber latex by 4 manufacturers were subjected to static testing under dry and wet conditions. The elastics consisted of 3 sizes: 3/16, 1/4, and 5/16 inch lumen sizes, each with forces specified according to the standard extension index of three times the lumen diameter. Most of the elastics did not match the specified index using the dry tests, but this should not be a serious clinical concern as all elastics showed acceptable regularity of force-extension characteristics. There was notable force degradation of all elastics when subject to water immersion, approximating 30% during the hour, but with an average less than 7% further loss up to 3 days. There were significant differences in force extension and force degradation characteristics between different extensions and force magnitudes for the elastics of the different manufacturers. It is suggested that the clinician could use the table of force degradation values for different extensions to select an appropriate elastic.