Biosensors & Bioelectronics

Three novel chemically modified Carbon Paste Sensors (CMCPs) were proposed for the determination of nafronyl potentiometric in bulk, pharmaceutical dosage form; human plasma/urine. The sensors were based on an ion-pair associates of nafronyl silicotungstic acid (Nf-St) (sensor 1), nafronyl silicomolybdic acid (Nf-SM) (sensor 2), a mixture of (Nf-St)+(Nf-SM) (sensor 3). The modified sensors showed Nernstian slopes ranging from 58.5 ± 0.5-60.7 ± 0.5 mV over the concentration ranged from 1.0x10^-7-1.0x10^-2 M and pH 2.0-6.0 with detection limit 0.1 nM. The sensors exhibited good selectivity for nafronyl with respect to inorganic/organic cations, sugars and amino acids. The calibration curve, standard addition and potentiometric titration methods were applied for the determination of nafronyl ion in its bulk powder, pharmaceutical dosage form, and human fluids plasma/urine taken from a healthy volunteer and for the monitoring Praxilene tablets in vitro dissolution rates. Sensor 3 had been the best sensitivity so was successfully used for the determination the solubility products of ion-pair associates. The results were excellent and satisfactory recovery comparable to those obtained with the British Pharmacopoeia.

The development of chemical sensors has received a great deal of scientific interest in the last decades. Not only the chemical industry may benefit from these sensors but also the food industry, bio-industry, medicine, environmental control because of their capability to give continuously and reversibly a selective and fast response to the presence of a specific compound in a complex mixture of components, without perturbing the system. Biosensors combine the power of analytical detection techniques with the specificity of biological recognition system and therefore they are the most promising devices today about this selectivity. Furthermore, biosensors possess many unique features such as compact size, simplicity of use, one-step reagentless analysis, absence of radioactivity, etc., that make them very attractive alternatives to conventional bioanalytical techniques. The present short review highlights some modern aspects of Chemically Modified Electrodes (CMEs) based on redox enzymes used in amperometric biosensing, a detection method which has already found a large number of applications in health care, food industry and environmental analysis. Some relevant applications of amperometric biosensors based on CMEs to real sample analysis are also presented and some possible future trends highlighted.

Peanut allergy, the most common cause of fatal-food-related anaphylaxis, is a lifelong disorder and the only existing therapy is avoidance of allergen-containing food. Detection of Ara h 1, the most important peanut allergen, is commonly performed by immunoassay techniques relying on the use of expensive and relatively unstable antibodies. Aptamers can overcome these drawbacks and offer a great potential for the development of reliable biosensors. Therefore, we will present a novel aptamer-based sensor for the label-free detection of Ara h 1. Amino (NH₂)-terminated Ara h 1 aptamers were covalently attached to carboxylated gold surfaces employing carbodiimide chemistry. This functionalization procedure was followed in real time by electrochemical impedance spectroscopy and quartz crystal microbalance with dissipation monitoring. Subsequently, the functionalized surfaces were exposed to Ara h 1 solutions in TGK buffer. By combining the two techniques, we can measure in a wide concentration regime varying from the low nanomolar range (1-15 nM) via electrochemical impedance spectroscopy to the higher concentrations (25-250 nM) by microgravimetric detection. In summary, a fast, low-cost and sensitive sensor platform for Ara h 1 detection has been developed, which can be operated as a ‘stand-alone device’, making it well suited for applications such as the screening of trace allergens.

We reported progressive metatarsal lenghtening by external fixator after osteotomy by open approach without bone interposition in a case of brachymetatarsia upon the third and fourth metatarsals. After a tomodensitometry planification, the biometry of the five metatarsal bones was done by X-ray and CT scan by measuring each metatarsal length (1 to 5) in the sagittal, horizontal and coronal plans and angles. The average amount of lengthening was 17 mm for the third and 15 mm the fourth at the end, 40% of the original length (range, 36 to 44%). In the same time, we treated hallux valgus by osteotomy. Decrease of motion and joint deformity did not occur. The control of the CT scan allowed choosing the real orientation and length of the two metatarsal bones to obtain an adequate parabola. Measurements with CT scan were more reliable than Xray.

Aptasensors for detection of thrombin were produced by covalently linking aptamer (ssDNA) to cSWCNT. Those biosensors were fully characterized by cyclic voltammetry to evaluate the electrode surface charge/ligand density. We performed the CV studies of electrostatically bound [Ru(NH₃)₆]³⁺ redox markers on aptamer surfaces and calculated aptamer surface charge density from the CV data. Potentiometric detection of thrombin allows then the correlation with the CV results. The electrode surfaces containing higher amount of aptamers exhibited better performance in potentiometric measurements. These investigations will introduce the pathway to build reusable and regenarable aptasensors including a simple, accurate and precise estimation of aptemer surface charge density to characterize the surface and hence to ensure the quality of apatsensors.

In this paper, the use of optical capsule for drug delivery with security is proposed. In principle, the optical capsules are generated and formed by soliton pulses within a small scale optical waveguide. The trapped molecules (drug molecules) are brought and stably confined within the device, which can move and deliver securely by the capsule gradient force to the required targets. By using the optical switching control, the trapped drugs within the specific capsules can leave to the access points via the through or drop port, where in this case the switching control is employed by light via the control port (add port). Simulation results obtained have shown that the capsule array can also be constructed and formed the large volume of drug delivery, while the switching control can form the uncapsule drugs into the drug target points. In application, the capsule array can be generated and formed the life molecule trapping, which can be available for life molecule transport within the device, for instance, stem cells, which is useful for stem cells dynamically movement, i.e. transportation to the required targets or organs.

A new concept of molecular motor using optical tweezers within a modified optical add–drop filter known as PANDA ring resonator is proposed. In simulation, dark and bright solitons are input into the system. The orthogonal tweezers can be formed within the system and detected simultaneously at the output ports. Under the resonant condition, the optical tweezers generated by dark and bright soliton pair corresponding to the left-hand and right-hand rotating solitons (tweezers) can be generated. In application, the trapped molecules can be moved and rotated to the required destinations, which can be useful for healthcare applications, especially, in drug delivery, medical diagnosis and therapy.