A Miniaturized Nafion-Based Glucose Sensor: in vitro and in vivo evaluation in dogs

1994 ◽  
Vol 17 (2) ◽  
pp. 88-94 ◽  
Author(s):  
F. Moussy ◽  
D.J. Harrison ◽  
R.V. Rajotte
Keyword(s):  
Glucose Sensor ◽  
Reference Electrode ◽  
The Body ◽  
In Vitro Tests ◽  
In Vivo Evaluation ◽  
Heat Curing ◽  
Layer Membrane ◽  
Outer Coating

We have developed an implantable glucose sensor based on a new tri-layer membrane configuration. The needle-type sensor integrates a Pt working electrode and a Ag/AgCI reference electrode. Its size is equivalent to a 25 gauge needle (0.5 mm in diamater). Poly (o-phenylenediamine) was used as an inner coating to reduce interference by small compounds present in the body fluids, and the perfluorinated ionomer, Nation as a biocompatible, protective, outer coating. Glucose oxidase trapped in an albumin/glutaraldehyde matrix was sandwiched between these coatings. In vitro tests in buffer showed the sensors had a good selectively, a sensitivity of about 25 nA/mM, and a 90% response time of 33 s. Stabilization of the current following polarization required 10 to 30 min in vitro and 30 to 40 in vivo. Although these sensors remained stable for many weeks in saline solution, their implantation in animals resulted in the degradation of the protective Nation outer coating, which in turn, led to the failure of the incorporated reference electrode. We demonstrated that if unprotected, the AgCI layer of the reference electrode rapidly dissolves in the biological environment. However, we later showed that in vivo degradation of Nation can be prevented by heat curing. When heat cured sensors were subcutaneously implanted in dogs, the sensors' signal closely followed the plasma glucose level during glucose tolerance tests. The response of the sensors implanted in dogs was retained for 10 days.

In Vitro Evaluation of Miniaturized Amperometric Enzyme Sensor Based on the Direct Electron Transfer Principle for Continuous Glucose Monitoring

2022 ◽  
pp. 193229682110706
Author(s):  
Yutaro Inoue ◽  
Yasuhide Kusaka ◽  
Kotaro Shinozaki ◽  
Inyoung Lee ◽  
Koji Sode
Keyword(s):  
Electron Transfer ◽  
Continuous Glucose Monitoring ◽  
Glucose Sensor ◽  
Direct Electron Transfer ◽  
Glucose Dehydrogenase ◽  
Glucose Monitoring ◽  
Reference Electrode ◽  
Enzyme Sensor

Background: The bacterial derived flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase (FADGDH) is the most promising enzyme for the third-generation principle-based enzyme sensor for continuous glucose monitoring (CGM). Due to the ability of the enzyme to transfer electrons directly to the electrode, recognized as direct electron transfer (DET)-type FADGDH, although no investigation has been reported about DET-type FADGDH employed on a miniaturized integrated electrode. Methods: The miniaturized integrated electrode was formed by sputtering gold (Au) onto a flexible film with 0.1 mm in thickness and divided into 3 parts. After an insulation layer was laminated, 3 openings for a working electrode, a counter electrode and a reference electrode were formed by dry etching. A reagent mix containing 1.2 × 10−4 Unit of DET-type FADGDH and carbon particles was deposited. The long-term stability of sensor was evaluated by continuous operation, and its performance was also evaluated in the presence of acetaminophen and the change in oxygen partial pressure (pO2) level. Results: The amperometric response of the sensor showed a linear response to glucose concentration up to 500 mg/dL without significant change of the response over an 11-day continuous measurement. Moreover, the effect of acetaminophen and pO2 on the response were negligible. Conclusions: These results indicate the superb potential of the DET-type FADGDH-based sensor with the combination of a miniaturized integrated electrode. Thus, the described miniaturized DET-type glucose sensor for CGM will be a promising tool for effective glycemic control. This will be further investigated using an in vivo study.

scholarly journals Pharmaceutical Benefits of Fluticasone Propionate Association to Delivery Systems: In Vitro and In Vivo Evaluation

Pharmaceutics ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 521 ◽  
Author(s):  
Marina G. Dogbe ◽  
Ambinintsoa Yattussia Mafilaza ◽  
Carla Vânia Eleutério ◽  
Helena Cabral-Marques ◽  
Sandra Simões ◽  
...  
Keyword(s):  
Extraction Procedure ◽  
A549 Cells ◽  
Free Form ◽  
In Vitro Tests ◽  
In Vivo Evaluation ◽  
Pulmonary Administration ◽  
Cell Compatibility ◽  
Intranasal Instillation

The objective of the present work was to characterize the ability of liposomes and cyclodextrin (CyD) complexes to modulate the in vivo profile of fluticasone (FTZ). In vitro cell compatibility tests were performed, exposing A549 cells to FTZ in the free form and FTZ associated to liposomes and complexed with CyD. The in vivo fate of a selected FTZ liposomal formulation and of several FTZ CyD complexes was achieved following intranasal instillation or pulmonary administration in BALB/c mice, respectively. For pulmonary administration, an inhalation chamber was constructed to enable the simultaneously pulmonary administration to six mice. Thirty minutes and 3 h after administration, mice were sacrificed, their blood, lungs, livers, and spleens were removed, and FTZ level was determined by HPLC using an extraction procedure. The in vitro tests revealed no toxic effects of FTZ formulations, as cellular viability was always superior to 90% for FTZ concentrations ranging from 5 to 60 µM 72 h after incubation. The in vivo biodistribution results showed that FTZ incorporated in liposomes resulted in 20 and 30 times higher accumulation in the lungs in comparison with free FTZ, at 0.5 and 3 h after i.n. administration, respectively. FTZ associated to Hydroxypropyl-γ-cyclodextrin (HP-CyD) was the complex that permitted the higher accumulation of FTZ in the lungs in comparison with the respective free form. The results also suggest that the inhalation chamber apparatus can effectively facilitate the evaluation of in vivo inhalation. The establishment of an animal model of asthma allows us to further study the therapeutic efficacy of the developed FTZ formulations.

scholarly journals An Amperometric Glucose Sensor Integrated into an Insulin Delivery Cannula: In Vitro and In Vivo Evaluation

2017 ◽  
Vol 19 (4) ◽  
pp. 226-236 ◽  
Author(s):  
W. Kenneth Ward ◽  
Gabriel Heinrich ◽  
Matthew Breen ◽  
Sheila Benware ◽  
Nicole Vollum ◽  
...  
Keyword(s):  
Glucose Sensor ◽  
Insulin Delivery ◽  
In Vivo Evaluation ◽  
Amperometric Glucose Sensor

scholarly journals A pH-Responsive Multifunctional Nanocarrier in the Application of Chemo-Photodynamic Therapy

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaohong Hu ◽  
Ziyu Gao ◽  
Huaping Tan ◽  
Long Zhang
Keyword(s):  
Anticancer Drug ◽  
Ph Value ◽  
Water Solution ◽  
Drug Carriers ◽  
The Body ◽  
Ph Responsive ◽  
In Vivo Evaluation ◽  
Coarse Surface

In cancer therapy, combined utilization of anticancer drug and photosensitizer attracts increasing interest due to enhanced curative effects and reduced side effects. Since the drug delivery system is an effective method to enhance curative effects, drug carriers for codelivery of the two abovementioned molecules are essentially important for chemophotodynamic therapy. Based on the foundation, a nanocarrier with pH-responsive and targeted properties was designed, prepared, and researched in the work. A pH-sensitive nanoparticle was fabricated by acetylated β-cyclodextrin (Ac-β-CD) using oil-in-water (O/W) emulsion technique. During the fabrication processing, a functional emulgator (gelation-folic acid ester (G-FA)) with a biorecognition domain was absorbed onto the surface of the nanoparticle, which endowed a nanoparticle-targeted property. The nanoparticle exhibited a coarse surface, pH-responsive property, and similar fluorescence characteristic as G-FA. The cell endocytosis profile revealed that equilibrium endocytosis could be reached after being cocultured with 1.0 mg/mL nanoparticle for 8 h. Furthermore, camptothecin (CPT) as an anticancer drug and phthalocyanine (PcZn) as a photosensitizer were encapsulated into the nanoparticle during the fabrication processing. The nanoparticle enhanced the fluorescence effects of PcZn on water solution, and CPT encapsulation proportion was slightly influenced by initial CPT concentration. The pH value influenced the PcZn fluorescence behavior and CPT release behavior of the nanoparticle. In vitro cytoviability evaluation confirmed the therapeutic effect of the nanocarrier on HEP2 cells. Finally, the results of preliminary in vivo evaluation revealed that the reported nanocarrier in the research could inhibit cancer development with little effects on the body weight of mice.

scholarly journals The in Vivo Evaluation of the Hemostatic Function of Stored Human Platelets

1977 ◽  
Author(s):  
M. Blajchman ◽  
A. Senyi ◽  
J. Hirsh
Keyword(s):  
Platelet Count ◽  
Platelet Function ◽  
Bleeding Time ◽  
Human Subjects ◽  
Human Platelets ◽  
In Vitro Tests ◽  
In Vivo Evaluation ◽  
Ethyl Palmitate

The assessment of the hemostatic function of stored human platelets is difficult to assess in human subjects. The use of thrombocytopenic rabbits treated with ethyl palmitate to produce reticuloendothelial blockade, has made it possible to study the hemostatic function of human platelets in vivo. The assessment of hemostatic function has been made using both a jugular bleeding time technique and an ear bleeding time technique, and in both, a close correlation between bleeding time and platelet count has been established. Using both methods, both fresh and human platelets stored for 72 hours at 22°C correct the bleeding time of thrombocytopenic animals to levels appropriate to the platelet count achieved. Platelets stored at 4°C using standard methods of preparation and storage were ineffective hemostatically after 24 hours storage. Platelets prepared and stored at 4°C at a pH of 6.4 were hemostatically effective in thrombocytopenic rabbits for as long as 10 days of storage. No correlation, however, was noted between the hemostatic effect of stored platelets and in vitro tests of platelet function. Similarly, the intravenous infusion of ADP and collagen produced similar falls in platelet count for both hemostatically effective and non-effective platelets. These studies provide further evidence for the limitations of in vitro tests of platelet function for the assessment of the potential in vivo function of stored human platelets. Furthermore, these findings raise the possibility for the prolongued liquid storage of human platelets at conditions which minimize bacterial contamination, yet maintain hemostatic efficacy.

Calibration of a Wearable Glucose Sensor

1992 ◽  
Vol 15 (1) ◽  
pp. 55-61 ◽  
Author(s):  
F.J. Schmidt ◽  
A.L. Aalders ◽  
A.J.M. Schoonen ◽  
H. Doorenbos
Keyword(s):  
Blood Glucose ◽  
Healthy Volunteers ◽  
Glucose Oxidase ◽  
Glucose Sensor ◽  
Subcutaneous Tissue ◽  
The Body ◽  
Diabetic Patients ◽  
Type I

Calibration of glucose sensors proved difficult for electrodes with immobilized glucose-oxidase. The correlation between the sensitivity of the electrodes in vitro and in vivo appeared to be poor. We developed a new type of glucose sensor, based on a microdialysis system, in which an oxygen electrode is used as detector outside the body and the enzyme glucose-oxidase dissolved in water is used as a dynamic selector. The enzyme solution is pumped through a hollow fiber placed subcutaneously, before the fluid passes the detector. The glucose sensor was tested in the subcutaneous abdominal tissue of 12 healthy volunteers and 12 type I diabetic patients. Blood glucose was clamped at two levels to permit a two-point calibration of the sensor in vivo. These values correlated well with the in vitro calibration factors (r=0.949). In subcutaneous tissue the sensor measures 43 ± 9% of the blood glucose value, using the in vitro calibration factor. No differences were detected between healthy volunteers and diabetic patients.

In vitro and in vivo Evaluation of the Radiochemical Compound Based on 99mTechnetium Labelled DARPin 9_29 for Molecular Visualization of Malignancies Overexpressing Her2/neu

2020 ◽  
Vol 65 (1) ◽  
pp. 37-41
Author(s):  
O. Bragina ◽  
A. Vorobyeva ◽  
V. Tolmachev ◽  
A. Orlova ◽  
V. Chernov ◽  
...  
Keyword(s):  
In Vitro Study ◽  
Radiochemical Yield ◽  
Blood Stream ◽  
The Body ◽  
Diagnostic Methods ◽  
In Vivo Studies ◽  
In Vivo Evaluation ◽  
High Accumulation

Purpose: Evaluation of a radiopharmaceutical based on 99mTc-labeled targeted molecules DARPin9_29 for radionuclide diagnostics of malignancies with Her2/neu overexpression. Material and methods: The DARPin9_29 sequence was amplified from the plasmid pET-DARP-6HIS for the DARPin9_29-His6 gene expression in E. coli cells. The eluent of 99mTcO4– (400–500 μl, 4 GBq) was added to the kit and incubated at a temperature of 100 °C for 20 minutes. After incubation, 40 μl of tricarbonyl technetium was added to 168 μg of DARPin9_29 in 100 μl of PBS (sodium phosphate buffer), followed by incubation at 40 °C for 60 minutes. The radiochemical yield and purity were determined by thin layer radiochromatography, the purification was performed using NAP-5 cleansing columns (GE Healthcare). Cell lines with different levels of Her2/neu expression were used: SKOV-3> BT474 >> DU-145 for the determination of the radiopharmaceutical specificity. Her2/neu expressing cell line SKOV-3 was used for in vitro study. The study was conducted 6 hours after the administration of the drug. Results: The radiochemical yield was 72 ± 8 %, the radiochemical purity after purification was 98.7 ± 1.0 %. The stability in PBS (phosphate buffered saline) solution after 1 hour was 99.8 ± 0.2; after 3 hours – 98.2 ± 0.1. In vitro studies showed that the accumulation of explored compound was directly proportional to the level of Her2/neu expression in cells, while blocking the receptors with an excess of unlabeled protein showed a significant reduction in binding in the group of cells. Data on biodistribution and SPECT/CT in the body of the animal BALB/c nu/nu demonstrated rapid removal of the compound from the blood stream and high accumulation in the liver, kidney and bladder 6 hours after the introduction of the radiopharmaceutical. Conclusion: The studies demonstrated high radiochemical yields and purity, as well as stability of the studied compound. The results of in vitro and in vivo analysis showed the specificity and affinity of the radiopharmaceutical to the Her2/neu receptor on the surface of tumor cells. The high accumulation of the drug in the liver and kidneys, detected in in vivo studies, is probably due to the lipophilicity of the 99mTc(CO)3-histidine tag and indicates the limitation of its further clinical use in assessing the condition of the above organs, which will require additional diagnostic methods, as well as possible modification chemical structure.

scholarly journals Assessment of Three In Vitro Tests and an In Vivo Test for Chloroquine Resistance in Plasmodium falciparumClinical Isolates

1998 ◽  
Vol 36 (1) ◽  
pp. 243-247 ◽  
Author(s):  
Jean Bickii ◽  
Leonardo K. Basco ◽  
Pascal Ringwald
Keyword(s):  
Host Factors ◽  
Chloroquine Resistance ◽  
In Vitro Assays ◽  
In Vitro Tests ◽  
In Vitro Test ◽  
In Vivo Evaluation ◽  
In Vivo Test ◽  
Vitro Test

Three in vitro assays (the isotopic semimicrotest [700 μl per well; 24-well plates], the isotopic microtest [200 μl per well; 96-well plates], and the rapid in vitro test) and the standard in vivo test for chloroquine resistance were compared for 99 clinical isolates of Plasmodium falciparum obtained from symptomatic African patients. The 50% inhibitory concentrations determined by the two isotopic tests were similar and were highly correlated (r = 0.965; P < 0.05), showing a high concordance between the semimicrotest and the microtest. There was a moderate agreement between these two isotopic tests and the in vivo test. Most of the discordant results were probably due to host factors, including reinfections, pharmacokinetic variations, and immunologic response, which are eliminated in in vitro assays. The rapid in vitro test based on the inhibition of chloroquine efflux in the presence of verapamil was poorly concordant with the other tests. Despite some discordant results, isotopic in vitro assays are useful to characterize the phenotypes of individual isolates without the interference of host factors and are complementary to in vivo evaluation of drug efficacy. However, in vitro assays need to be standardized to allow direct comparison of results between different laboratories.

The Role of Polyphenols in the Modulation of Plasma Non-Enzymatic Antioxidant Capacity (NEAC)

2012 ◽  
Vol 82 (3) ◽  
pp. 228-232 ◽  
Author(s):  
Mauro Serafini ◽  
Giuseppa Morabito
Keyword(s):  
Antioxidant Capacity ◽  
Dietary Intervention ◽  
Ex Vivo ◽  
The Body ◽  
Dietary Polyphenols ◽  
Enzymatic Antioxidant ◽  
Endogenous Antioxidant

Dietary polyphenols have been shown to scavenge free radicals, modulating cellular redox transcription factors in different in vitro and ex vivo models. Dietary intervention studies have shown that consumption of plant foods modulates plasma Non-Enzymatic Antioxidant Capacity (NEAC), a biomarker of the endogenous antioxidant network, in human subjects. However, the identification of the molecules responsible for this effect are yet to be obtained and evidences of an antioxidant in vivo action of polyphenols are conflicting. There is a clear discrepancy between polyphenols (PP) concentration in body fluids and the extent of increase of plasma NEAC. The low degree of absorption and the extensive metabolism of PP within the body have raised questions about their contribution to the endogenous antioxidant network. This work will discuss the role of polyphenols from galenic preparation, food extracts, and selected dietary sources as modulators of plasma NEAC in humans.

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