Highly sensitive endotoxin detection using a gold nanoparticle loaded layered molybdenum disulfide-polyacrylic acid nanocomposite.

Endotoxins or lipopolysaccharides (LPS) are pathogens released from the outer membrane of gram-negative bacteria which produce toxic effects on humans. The sensitive and selective detection of LPS is in high demand, especially in the field of medical supplies, therapeutics and in the food industry. Herein we report a new nano-probe based on a gold nanoparticle loaded, water-soluble layered molybdenum disulfide-polyacrylic acid (Au/MoS2-PAA) nanocomposite as a label-free voltammetric aptasensor for ultrasensitive LPS detection. MoS2 nanosheets were obtained through one-step sonication assisted exfoliation of bulk MoS2 with polyacrylic acid (PAA). Au nanoparticles were incorporated into the MoS2-PAA nanocomposite and thiol terminated LPS binding aptamers (LBA) were immobilized on this. The specific binding of LPS with LBA is investigated electrochemically by differential pulse voltammetry. The apparent binding constant (Kb) of LPS with LBA has been calculated to be 1.53 × 102 mL g-1. The aptasensor demonstrated LPS detection down to the ag mL-1 level without incorporating any redox mediator and showed wide linearity from 100 ag mL-1 to 100 pg mL-1 with a low limit of detection of 29 ag mL-1. The sensor showed excellent recovery upon spiking LPS in clinical grade insulin, suggesting that LBA/Au/MoS2-PAA/GCE has promising application for the trace analysis of LPS in the field of pharmaceutical products.

Nondestructive Quantitative Inspection of Drug Products Using Benchtop NMR Relaxometry-the Case of NovoMix® 30.

Batch-level inference-based quality control is the standard practice for drug products. However, rare drug product defects may be missed by batch-level statistical sampling, where a subset of vials in a batch is tested quantitatively but destructively. In 2013, a suspension insulin product, NovoLog® Mix 70/30 was recalled due to a manufacturing error, which resulted in insulin strength deviations up to 50% from the labeled value. This study analyzed currently marketed FlexPen® devices by the water proton transverse relaxation rate using a benchtop nuclear magnetic resonance relaxometer. The water proton transverse relaxation rate was found to be sensitive to detecting concentration changes of the FlexPen® product. These findings support the development of vial-level verification-based quality control for drug products where every vial in a batch is inspected quantitatively but nondestructively.

Is insulin diluted when stored in water?

BACKGROUND: Insulin storage is a challenge in resource-poor countries. In Uganda, patients were noted to store insulin vials by submerging them in water. OBJECTIVE: To examine whether withdrawing insulin from a vial without adding air back causes a vacuum which allows water to enter the vial, resulting in insulin dilution. METHODS: Seven hundred units of insulin were withdrawn from forty 10 mL vials of 100 units/mL insulin [20 neutral protamine hagedorn (NPH), 20 regular]. In half, air was added back. The vials were weighed (baseline). Half of the vials (10 with added air, 10 without) were submerged in water for 24 h and then air-dried for 24 h. Vials that were not submerged sat at room temperature for 48 h. All vials were weighed 48 h from baseline. RESULTS: Addition of air did not impact the change in weight after submersion (air added: -0.002 ± 0.001 g or -0.2 ± 0.1 unit; no air added: -0.003 ± 0.000 g or -0.3 ± 0 unit, p = 0.57). In a subset of vials in which an additional 240 units were withdrawn before submersion for another 24 h, there was still no difference in weight change in those vials with air added (p = 0.2). CONCLUSION: Withdrawing insulin from a vial without adding air did not result in uptake of water or dilution of insulin in the submerged vial, although it made drawing up the insulin easier. This study did not address the larger concern of bacterial contamination of the rubber stopper during water storage.

Improved limit of detection and quantitation development and validation procedure for quantification of zinc in Insulin by atomic absorption spectrometry.

A simple and expeditious analytical method for determination of zinc in human insulin isophane suspension by flame atomic absorption spectrophotometer (FAAS) was validated. The method was carried out on atomic absorption spectrometer with 0.4 nm bandwidth, 1.0 filter factor on deuterium (D2) background correction. The integration time was set at 3.0 second with 5.0 mA lamp current. The parameters of method validation showed adequate linearity, efficiency and relative standard deviation values were between 0.64%-1.69% (n=7), 1.31%-1.58% (n=10) for repeatability and intermediate precision respectively. The limit of detection 0.0032 µg/mL, 0.0173 µg/mL, 0.0231 µg/mL and limit of quantitation 0.0107µg/mL, 0.0578 µg/mL, 0.0694 µg/mL based on signal to noise (SN), calibration curve method (CCM) and fortification of blank (FB) were obtained respectively. The percentages of recovery for low, medium and high spiked concentration levels of zinc in human insulin were 99.38 ± 0.04 to 100.3 ± 0.03, 98.45 ± 0.38 to 100.3 ± 0.07 and 99.42 ± 0.03 to 99.42 ± 0.08 respectively. With the use of this method, five samples from each vial of human insulin isophane suspension were analyzed and the zinc content was determined. The zinc content were 22.1 ± 0.025 µg/mL and 24.3 ± 0.028 µg/mL which compliance the British Pharmacopoeia standard.

Beyond the era of NPH insulin--long-acting insulin analogs: chemistry, comparative pharmacology, and clinical application.

The new rDNA and DNA-derived "basal" insulin analogs, glargine and detemir, represent significant advancement in the treatment of diabetes compared with conventional NPH insulin. This review describes blood glucose homeostasis by insulin in people without diabetes and outlines the physiological application of exogenous insulin in patients with type 1 and type 2 diabetes. The requirements for optimal basal insulin treatment are discussed and the methods used in the evaluation of basal insulins are presented. An essential criterion in the development of an "ideal" basal insulin preparation is that the molecular modifications made to the human insulin molecule do not compromise safety. It is also necessary to obtain a clear understanding of the pharmacokinetic and pharmacodynamic characteristics of the two currently available basal insulin analogs. When comparing glargine and detemir, the different molar concentration ratios of the two insulin formulations should be considered along with the nonspecificity of assay systems used to determine insulin concentrations. However, euglycemic clamp studies in crossover study design provide a good basis for comparing the pharmacodynamic responses. When the latter is analyzed by results of intervention clinical trials, it is concluded that both glargine and detemir are superior to NPH in type 1 and type 2 diabetes. However, there is sufficient evidence to demonstrate that these two long-acting insulin analogs are different in both their pharmacokinetic and pharmacodynamic profiles. These differences should be taken into consideration when the individual analogs are introduced to provide basal insulin supplementation to optimize blood glucose control in patients with type 1 and type 2 diabetes as well. PubMed-Medline was searched for articles relating to pharmacokinetics and pharmacodynamics of glargine and detemir. Articles retrieved were reviewed and selected for inclusion if (1) the euglycemic clamp method was used with a duration >or=24 h, (2) a single subcutaneous dose of glargine/detemir was used, and (3) area under the curve for insulin concentrations or glucose infusion rates were calculated.

Structural characterization of insulin NPH formulations.

Insulin NPH (neutral protamine hagedorn) has for long been one of the most important therapeutic formulations for the treatment of diabetes. The protracted action profile of NPH formulations is gained from crystallizing insulin with zinc in the presence of the basic poly-arginine peptide protamine. In spite of its long history and successful use, the binding mode of the insulin-protamine complex is not known. In this study, three different systems were used to study protamine binding to insulin. In the first system, crystals of an insulin-protamine complex grown in the presence of urea and diffracting to 1.5A resolution were analyzed. In the second system, a shorter peptide consisting of 12 arginine residues was co-crystallized with insulin in order to reduce the flexibility and thereby improve the electron density of the peptide. Both systems yielded data to a significantly higher resolution than obtained previously. In addition, a third system was analyzed where crystals of insulin and protamine were grown in the absence of urea, with conditions closely resembling the pharmaceutical formulation. Data from these NPH microcrystals could for the first time be collected to 2.2A resolution at a micro focused X-ray beamline. Analysis of all three crystal forms reveal potential protamine density located close to the solvent channel leading to the centrally located zinc atoms in the insulin hexamer and support that protamine binds to insulin in a not well defined conformation.

Platelet activation in the presence of neutral protamine Hagedorn insulin: a new feature of antibodies against protamine/heparin complexes.

Essentials Protamine (PRT) is used to stabilize insulin in neutral protamine Hagedorn (NPH) insulin. The interaction between NPH-insulin, anti-PRT/heparin antibodies and platelets was investigated. Anti-PRT/heparin antibodies activate platelets in presence of NPH-insulin dependent on heparin. Cross-reactivity seems to have no major effect on the clinical outcome of medical patients. SUMMARY: Background Protamine (PRT) is used to stabilize insulin in neutral protamine Hagedorn (NPH) insulin, a commonly used therapeutic agent for diabetes mellitus. Immunization against PRT/heparin complexes is common in diabetic patients. Objectives To investigate the impact of NPH-insulin on the interaction between anti-PRT/heparin antibodies and platelets. Methods The interaction between NPH-insulin and anti-PRT/heparin antibodies was tested using in-house enzyme immunoassays. The ability of anti-PRT/heparin antibodies to activate platelets in the presence of NPH-insulin (and heparin) was investigated using flow cytometry. Results Twenty-one out of 80 sera containing anti-PRT/heparin IgG showed binding to NPH-insulin. Anti-PRT/heparin IgG from immunized patients bound to platelets in the presence of NPH-insulin, but not in the presence of native insulin. Anti-PRT/heparin antibodies induced P-selectin expression in the presence of NPH-insulin in a heparin-dependent way (median mean fluorescence intensity in the presence of NPH-insulin: 55, 95% confidence interval [CI] 18.7-100.5 vs. NPH-insulin and heparin: 204, 95% CI 106.5-372.8). The clinical relevance of platelet-activating anti-PRT/heparin antibodies was assessed by investigating a multicenter study cohort of 332 acutely ill medical patients who received heparin. None of the 21 patients with anti-PRT/heparin IgG developed thrombocytopenia or thromboembolic complications. Conclusions Anti-PRT/heparin antibodies activate platelets in the presence of NPH-insulin in a heparin-dependent way. However, results from our preliminary study indicate no major impact of these antibodies on the clinical outcome in medical patients receiving heparin, particularly on thromboembolic complications.

Bioavailability and variability of biphasic insulin mixtures.

Absorption of subcutaneously administered insulin is associated with considerable variability. Some of this variability was quantitatively explained for both soluble insulin and insulin suspensions in a recent contribution to this journal (Søeborg et al., 2009). In the present article, the absorption kinetics for mixtures of insulins is described. This requires that the bioavailability of the different insulins is considered. A short review of insulin bioavailability and a description of the subcutaneous depot thus precede the presentation of possible mechanisms associated with subcutaneous insulin degradation. Soluble insulins are assumed to be degraded enzymatically in the subcutaneous tissue. Suspended insulin crystals form condensed heaps that are assumed to be degraded from their surface by invading macrophages. It is demonstrated how the shape of the heaps affects the absorption kinetics. Variations in heap formation thus explain some of the additional variability associated with suspended insulins (e.g. NPH insulins) compared to soluble insulins. The heap model also describes how increasing concentrations of suspended insulins lead to decreasing bioavailability and lower values of Cmax. Together, the findings constitute a comprehensive, quantitative description of insulin absorption after subcutaneous administration. The model considers different concentrations and doses of soluble insulin, including rapid acting insulin analogues, insulin suspensions and biphasic insulin mixtures. The results can be used in both the development of novel insulin products and in the planning of the treatment of insulin dependent diabetic patients.

Assessment of the mixing efficiency of neutral protamine Hagedorn cartridges.

Reliable application of neutral protamine Hagedorn (NPH) insulin requires previous resuspension of the suspension by tipping over the cartridge 20 times. This procedure is considered annoying by patients. The goal of this investigation was to assess the efficiency of the mixing procedure when performed less frequently than recommended. Neutral protamine Hagedorn insulin cartridges from five different manufacturers (sanofi-aventis, Lilly, Berlin-Chemie, B. Braun, and Novo Nordisk) were emptied with doses of 28 IU in the morning and the evening over 5 days. While the first dose was obtained after a regular resuspension procedure (20x tipping over), the consecutive doses were obtained after 3, 6, 10, or 20 mixing procedures (12 cartridges per experimental series, two doses/day). Insulin concentrations of doses 1, 2, 6, and 10 were determined by high-pressure liquid chromatography. Between dosing, cartridges were stored at room temperature in a horizontal position. Comparable insulin concentrations were seen in the first correctly prepared doses. Pronounced and substantial deviations from the selected dose were observed with most of the cartridges, in particular when resuspending only 3 and 6 times. Mean absolute percentage deviations when tipping 3 times and maximally observed overdoses were: Insuman basal: 1.1 +/- 1.0%/4 IU, Humulin N: 2.6 +/- 3.4%/19 IU, Berlinsulin H basal: 4.4 +/- 6.0%/26 IU, Insulin B. Braun basal: 10.4 +/- 8.9%/38 IU, and Protaphane: 4.7 +/- 4.1%/19 IU (all p < 0.05 vs Insuman basal). Only one cartridge with three metal mixing bullets (sanofi-aventis) was resuspended efficiently with only a few mixing procedures. All other cartridges with fewer bullets were shown to deliver potentially harmful doses if used for treatment when the mixing procedure was less frequent than demanded in the instructions for use.

An analysis of the mixing efficiency of neutral protamine Hagedorn cartridges.

In this issue of Journal of Diabetes Science and Technology, Kaiser and colleagues conducted an investigation to identify variations in the delivered dose of several different isophane insulin (neutral protamine Hagedorn, NPH) brands that use glass and metal bodies ("bullets") to facilitate mixing. Using a strategy where multiple pens from each of five different NPH insulin products (Insuman Basal, sanofi-aventis, three metal bullets; Humulin N, Lilly, one glass bullet; Berlinsulin H Basal, Berlin-Chemie, one glass bullet; Insulin B. Braun Basal, two glass bullets; and Protaphane Penfill, NovoNordisk, one glass bullet) were compared at multiple sampling points and over a range of mixing procedures (3, 6, 10, and 20 times), the authors identified deviations in the delivered dose of insulin at initial use and with repeated dosing. At the initial dose, adhering with manufacturer recommendations to conduct the mixing procedure 10-20 times was found to demonstrate minimal deviation and there was no pronounced difference among the products. Decreasing the number of mixing procedures from 10-20 to 3-6 times, a more profound deviation was noted, with the Insuman Basal product demonstrating less variability in comparison to all other products evaluated. A repeated dose study (1, 2, 6, and 10) with only six mixing procedures revealed that the insulin concentration of each dose increased for all products except Insuman Basal. Clinically, numerous factors may contribute to variability observed with subcutaneous administration of isophane insulin. While data presented by Kaiser and colleagues demonstrated that the issue of proper mixing is not trivial, the modest differences observed between and within products both at the initial dose and with repeated dosing may indicate that the clinical relevance of these findings is most applicable to those requiring large doses or, alternatively, those who have otherwise unexplained hypoglycemic episodes.

Estimations of average particle sizes and size distributions of commercially available human-insulin aqueous suspensions using laser-light diffraction spectroscopy.

The average diameter and size distribution of particles in commercially available isophane-insulin and zinc-insulin aqueous suspensions (11 products) were examined using laser-light diffraction spectroscopy (LLDS). Wide variation was observed between products in volume-weighted and number-weighted average diameters. The particles in the insulin aqueous suspensions were found to be mono-dispersed within relatively narrow size distributions. Sonication for a short time led to a downshift in the apparent average diameter, which was most remarkable with isophane-insulin aqueous suspensions. This could be ascribed to dispersion of aggregated needle-like crystals and/or crystal breakage. In the case of biphasic isophane-insulin aqueous suspensions, the average size as well as the size distribution shifted toward the smaller end of the scale with decrease in the isophane content.

Stability and sterility of biosynthetic human insulin stored in plastic insulin syringes for 28 days.

The stability and sterility of biosynthetic human insulin products stored at refrigerator and room temperatures in two types of plastic syringes and the stability of preservatives in the products were studied. Four types of biosynthetic human insulin were used: regular, isophane, combination, and extemporaneously prepared combination. Samples (0.4 mL) were withdrawn from multiple-dose vials into 39 polypropylene and 39 propylene-ethylene copolymer syringes. Three syringes of each type were analyzed immediately; the remaining syringes were stored in plastic bags, half at room temperature (23 degrees C) and half in the refrigerator (4 degrees C). A vial of each type of insulin was maintained under similar conditions. At days 1, 3, 7, 14, 21, and 28, samples from each syringe were analyzed by high-performance liquid chromatography for insulin potency and m-cresol and phenol concentrations. Samples of each product were also tested for sterility after 1, 2, and 4 weeks of storage at 4 degrees C and 23 degrees C. The potency of insulin in each of the biosynthetic human insulin products did not change significantly during the 28-day study in both types of plastic syringes and at both temperature settings. m-Cresol concentrations decreased in all samples; greater decreases occurred in samples stored at room temperature and in samples stored in polypropylene syringes. Phenol concentrations were less affected than m-cresol concentrations; greater decreases occurred in samples stored at room temperature. No significant decreases in insulin potency or m-cresol or phenol concentrations occurred in control samples stored in vials kept under similar conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

[Flocculation of NPH insulin]. / Floculación de la insulina NPH.

In the past decade, human insulins have been substituting animal insulins, offering the advantage of its lesser antigenic capacity. One of the most clinically important problems with human NPH insulins is its tendency to flocculate. We present four diabetic patients who, after using flocculated human NPH insulin, encountered a deterioration in the metabolic control of their diabetes, and in two of them, there were bouts of diabetic Ketoacidosis "without any other apparent causal factors". Among those causes favoring flocculation are movement during transport, high temperatures, and probably leaving the vial open for an excessively long period of time, as with the extraction of multiple doses. Physicians, educators, diabetics, and their relatives should be informed of this phenomenon. Diabetics, especially those who carry insulin with them, should carefully inspect their vials before each injection to detect signs of flocculation.

Immunologic analysis of anaphylaxis to protamine component in neutral protamine Hagedorn human insulin.

We report the clinical and immunologic analysis of two patients with diabetes who had anaphylaxis to neutral protamine Hagedorn (NPH) human insulin in the absence of allergy to regular insulin. A 36-year-old woman without a recent history of local insulin reactions or interruption of insulin therapy experienced anaphylaxis within 15 minutes of her usual morning dose of subcutaneously administered NPH human insulin. A 62-year-old man with a history of generalized reactions to NPH human insulin and of anaphylaxis to intravenously administered protamine had generalized urticaria after injection of NPH human insulin. Both patients subsequently tolerated Lente human insulin. Skin test results in both patients were negative to regular and Lente insulin preparations but positive to NPH insulin and to protamine at concentrations tested. In vitro assays demonstrated that both patients had markedly elevated serum levels of IgE and IgG to protamine, but not to regular human insulin, and that their IgE antibodies to protamine recognized protamine antigenic determinants in NPH human insulin. We conclude that the anaphylactic reactions to NPH insulin in our patients were mediated by IgE to protamine, which should be a pathogenetic consideration in the evaluation of immediate-type reactions to protamine-containing insulins.