Stability Studies Research Articles

Mechanistic study of synergetic stabilization of Pickering emulsions by corn glutelin and starch complexes

The hydrophobicity of glutelin, zein, and carotenoids has limited the development of corn-based functional food products. This paper aims to construct emulsions stabilized by multiple corn-derived components using a simple and organic solvent-free method. The emulsions comprised oil droplets dispersed in the water, where glutelin and starch were stabilizers. Optimal stability, smaller droplet sizes, and moderate viscosity were achieved with a glutelin/starch ratio of 1:4. The results of the dynamic rheological measurements of bulk emulsions as well as interfacial properties and microstructure revealed that the stability mechanism of glutelin-starch complex was the interplay of the increased continuous phase viscosity and stronger interfacial viscoelastic films. Thus, these combined factors effectively inhibited the creaming and coalescence of oil droplets. Interfacial films also protected the carotenoids. The results of this study elucidate the stabilization mechanism among different corn-derived components and therefore guide the design of corn-based personalized nutritional systems.

Isolation and characterization of a degradation product of mexiletine hydrochloride using FT-IR, LC-MS and NMR: method development and validation of stability indicating RP-HPLC method for quantification of characterized impurity

Mexiletine Hydrochloride is an antiarrhythmic drug used to treat acute and chronic ventricular arrhythmias. Significant degradation of unknown impurity was observed while evaluating the impurity profile of the Mexiletine Hydrochloride stability studies. The levels of the unknown impurity are more than the regulatory identification/qualification threshold level (0.08%). Mexiletine was forcefully subjected to various stress conditions, such as acidic, basic, oxidation, photolysis, and thermal. Among these stress conditions, we identified an unknown degradation impurity in the thermal stress (105°C for 15 days) of Mexiletine, the same as that of an unknown impurity observed in the stability studies. The present research reports the isolation of unknown impurity in thermal stress by preparative HPLC and the characterization of isolated unknown degradation impurity using LC-MS, FT-IR, and NMR techniques. The spectral data elucidated the structure of the degradation product, and it was identified as “(E)-2-(((1-(2,6-dimethylphenoxy)propan-2-yl)imino)methyl)-6-methylphenol”. A stability-indicating HPLC method was developed and validated to determine and quantify the degradation product in Mexiletine Hydrochloride. The levels of the unknown degradation product reduced to below the limit of detection (<0.007%) from 0.10% after applying its relative response factor “16.5” and complying with the regulatory threshold limits. It helps to extend the shelf life of Mexiletine.

Current regulatory requirements for stability studies of biological medicinal products: a review

INTRODUCTION. The stability assessment of biological medicinal products (BMPs) requires special approaches and regulatory requirements. Therefore, BMPs require relevant national guidelines, which are an important prerequisite for the assurance of the safe and effective use of BMPs.AIM. This study aimed to analyse national and international requirements for the stability assessment of BMPs in order to use the results to inform future development of a unified regulatory approach to estimating and confirming shelf-life periods for BMPs.DISCUSSION. Most biotechnological medicinal products (BTMPs) are proteins and are highly sensitive to environmental factors by nature. Therefore, the shelf life of a BTMP is established on the basis of real-time stability studies. Stability testing under accelerated and stress conditions is conducted to support shelf-life claims and to characterise the mechanism of protein structure degradation. The results of accelerated and stress studies can be used to select the most sensitive stability-indicating parameters and testing methods. National and international regulatory authorities have developed specialised guidelines for stability studies of BMPs of various origins, and the stability assessment approaches in the regulatory system of the Eurasian Economic Union (EAEU) are harmonised with international standards. Special considerations associated with the stability of vaccines imply that stability studies of vaccines should not only establish shelf life but also investigate stability after reconstitution and after short-term temperature excursions from the recommended cold-chain conditions.CONCLUSIONS. Special stability testing considerations for various groups of BMPs (including BTMPs and immunobiologicals) indicate the need to develop and improve the system of requirements for BMP stability assessment. This will facilitate the optimisation of the life cycle of BMPs in the Russian Federation and the other EAEU member states.

Analytical study and control of high-speed vehicle hunting stability with traction/braking torque

Analytical study and control of high-speed vehicle hunting stability with traction/braking torque

Synthesis, vibrational, thermal, topological, electronic, electrochemical stability and DFT studies of new DABCO based ionic liquids

The design of new ILs with different anions could provide interesting physico-chemical properties and for these reasons, the knowledge about the synthesis, the thermal, vibrational, topological, electronic, electrochemical properties and interaction between the selected cation-anion in these ILs are important subjects. Therefore, the understanding about these properties of these compounds is an important subject of study. In this work, we studied three ionic liquids based on the 1-decyl-1,4-diazabicyclo[2.2.2]octane, DABCO-cation, where the corresponding anions were [Br]-, [PF6]-, and [N(SO₂CF₃)₂]-. The syntheses of these bicyclic DABCO ionic liquids are based on an alkylation reaction of 1,4-diazabicyclo[2.2.2] octane and 1-bromodecanefollowed by anion exchange. The obtained ILs are characterized by 1H, 13C, 19F and 31P-NMR spectroscopy. Vibrational spectroscopy studies are conducted by infrared (FTIR/ATR) and Raman spectroscopy in the wavenumber range 600–4000 cm-1 and 45–3500 cm-1, respectively. Furthermore, the thermal stabilities were investigated using the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) methods. Results indicate that the thermal stability follow the order [C10DABCO][Br]<[C10DABCO][PF6]<[C10DABCO][N(SO₂CF₃)₂]. Additionally, the structural parameters, electrostatic potential (ESP) maps, interaction energies, non-covalent interaction (NCI), atoms in molecule (AIM) analysis, natural bond orbital (NBO), frontier molecular orbital (FMO) analysis and Electrochemical window (ECW) are studied and analyzed by means of DFT calculations at the M06–2X-GD3/AUG–cc–pVDZ level of theory.

Acoustic resonance technology and quality by design approach facilitate the development of the robust tetrandrine nano-delivery system

The aim of this study was to develop a sufficiently robust tetrandrine (Tet) nano-delivery system using acoustic resonance (AR) technology and freeze-drying technology. This system can effectively improve the solubility and dissolution properties of Tet, along with high stability and scale-up adaptability. Firstly, 54 stabilizers were screened simultaneously in a high-throughput manner with the help of AR technology to fully explore the optimal prescription space of tetrandrine nanosuspension (Tet-NS). The Plackett-Burman design was used to screen for critical variables severely affecting the quality of Tet-NS. The Box-Behnken design was used to investigate and optimize critical variables to obtain optimal nanosuspensions. The optimal prescription was successfully scaled up by 100 times, which was the initial exploration of its commercial scale production. Solidification studies have shown that formulations with 2.44% fructose as the cryoprotectant have excellent redispersibility. Compared with pure Tet, Tet in Tet-NS showed a significant increase in solubility and dissolution rate in water. Fourier transform infrared (FT-IR) demonstrated that no significant interactions occurred between the drug and excipients in Tet-NS. Powder x-ray diffraction analysis (PXRD) indicated that some of the Tet transformed into amorphous state during the preparation process. In short-term stability study, Tet-NS successfully maintained its physical stability. In summary, under the guidance of the QbD concept, this study rapidly developed Tet-NS using acoustic resonance technology, which can effectively improve the solubility and dissolution properties of Tet. During the development of Tet-NS, AR technology has demonstrated high particle size reduction capability, the ability to process multiple sets of formulations in parallel, and excellent scale-up capability. Meanwhile, the method and concept of this study are not limited to Tet, but also applicable to other poorly water-soluble drugs.

Active Sites and Stability Study of Fe/N/C Catalyst in PEMFCs: A Decade of Stunning Progress and the Remaining Challenges

Active Sites and Stability Study of Fe/N/C Catalyst in PEMFCs: A Decade of Stunning Progress and the Remaining Challenges

The development and evaluation of chitosan-coated enzyme magnetic nanoparticles for cellulose hydrolysis

The recycling capability, colloidal and thermal stability of exo-cellulase, endo-cellulase, and β-glucosidases with magnetic particles (MNPs) were evaluated. Co-precipitation and oxidation of Fe(OH)2 methods were used to fabricate magnetic nanoparticles. Three different enzymes were covalently bound to the surface of MNPs using 3-(aminopropyl) triethoxysilane (APTES) and a common protein crosslinking agent, glutaraldehyde. To evaluate the increase in colloidal dispersion stability, chitosan-coating was applied on MNPs and evaluated through particle settlement tests. The results showed that the chitosan-coated MNPs had 3.7 times higher colloidal dispersion stability than the bare MNPs. X-ray photoelectron spectroscopy (XPS) confirmed each magnetic nanoparticle surface modification step and successful enzyme binding. The optimum bioconjugate ratio in exo-cellulase, endo-cellulase, and β-glucosidases was evaluated, and having a high endo-cellulase bioconjugate in the reaction produced the highest glucose. The bioconjugates showed superior glucose productivity 39.4% at 65°C and 22.2% at 88°C in which the native enzyme is inactivated completely after 5 h of exposure. Recycling stability studies showed approximately 78% of activity was retained after 10 cycles and 32% of activity was retained after 20 cycles. The bioconjugates demonstrated equivalent total product conversions as a single reaction of an equivalent amount of the native enzyme after the 10th cycle this work introduces a novel method for covalently binding individual exo-cellulase, endo-cellulase, and β-glucosidases. These bioconjugates showed superior thermal stability and recyclability. It was also demonstrated that chitosan coating significantly improves the colloidal dispersion stability of bioconjugates. Thus this work validates the use of enzyme-MNP bioconjugates to effectively glucose production and promising technique for eventual continuous biological processes.

Preparation and characterization of niosomes for the delivery of a lipophilic model drug: comparative stability study with liposomes against phospholipase-A2

Vesicular nanocarriers like niosomes and liposomes are widely researched for controlled drug delivery systems, with niosomes emerging as promising alternatives due to their higher stability and ease of manufacturing. This study aimed to develop and characterize a niosomal formulation for the encapsulation and sustained release of temozolomide (TMZ), a model lipophilic drug, and to compare the stability of niosomes and liposomes, with a particular focus on the behavior of their lipid bilayers. Niosomes were prepared using the thin-film hydration method, composed of Span 60 (Sorbitan monostearate), cholesterol, and soy lecithin in varying molar ratios. The study investigated critical properties such as drug loading capacity, release kinetics, and resistance to enzymatic degradation. The optimized formulation was analyzed for drug entrapment efficiency and stability against phospholipase A2 (PLA2) degradation. The optimized niosomal formulation, with a 4:2:1 molar ratio of Span 60: cholesterol, achieved a high TMZ entrapment efficiency of 73.23 ± 1.02% and demonstrated sustained drug release over 24 hours. In comparison, liposomes released their TMZ payload within 4 hours upon exposure to PLA2, while the niosomes maintained their release profile, indicating superior stability. Spectroscopic and thermal analysis confirmed successful drug encapsulation with no component incompatibilities.

A Uniqueness Theorem for Stability Problems of Functional Equations

In this paper, we present a uniqueness theorem obtained by using direct calculation. This theorem is applicable to stability problems of functional equations whose solutions are monomial or generalized polynomial mappings of degree n. The advantage of this uniqueness theorem is that it simplifies the proof by eliminating the need to repeatedly and cumbersomely prove uniqueness in stability studies.

A-057 Assessing Direct Renin Stability in EDTA Plasma Prior to Separation from Cells and Post-thaw

Abstract Background Renin is an enzyme secreted by the kidneys responsible for blood pressure regulation through the renin-angiotensin-aldosterone axis. Direct renin measurements are frequently used to investigate underlying causes of hypertension, including primary aldosteronism (PA), which is screened for using an aldosterone:renin ratio (ARR). Appropriate handling of renin samples in the preanalytical phase is critical, as cryoactivation of prorenin can occur when samples are refrigerated or cooled for extended periods of time, falsely elevating results. Manufacturer instructions for renin handling are often poorly defined and there is currently no consensus as to best handling practices. Two variables that frequently lead to renin sample rejections in our laboratory are time to centrifugation after collection and time kept at room temperature (RT). The objective of this study was to evaluate the stability of direct renin under ambient and freeze-thaw conditions in an effort to reduce test cancellations due to improper handling. Methods Plasma samples collected from five volunteers with consent in K2EDTA tubes were used for renin stability studies. Baseline renin samples were kept at RT for two hours after collection, centrifuged, measured, and subsequently frozen for post-thaw studies. To assess stability before separation from cells, samples kept at RT for two and four hours prior to centrifugation were assayed in triplicate for direct renin. For post-thaw stability studies, plasma samples were split into two aliquots each and frozen at -20⁰C for at least 24 hours, but no longer than 30 days. After removal from -20⁰C, one set of aliquots was thawed on the benchtop at RT and the second set was thawed in an RT water bath for up to one hour. Samples were centrifuged and assayed for direct renin in triplicate at baseline and six hours post-thaw. Direct renin was measured using the LIAISON XL chemiluminescent immunoassay (Diasorin). Bias was assessed after each treatment. The total allowable error (TEa) was ±2 pg/mL or ±20%. Results Measured renin concentrations ranged from 6.8-29.7 pg/mL. The percent bias in direct renin concentrations when comparing samples stored for two-hour and four-hour timepoints before centrifugation was 2.0% on average. Post-thaw studies comparing renin concentrations at the baseline and six-hour timepoints revealed an average percent bias of 13.1% and 12.2% for RT and water bath thawing methods, respectively. All samples tested were within the TEa. Conclusions Direct renin is stable in lavender K2EDTA tubes at RT for up to four hours, prior to centrifugation and separation from cells. Renin concentrations remained stable after storage at -20⁰C and thawing at RT for up to six hours, regardless of thawing method. By expanding direct renin stability criteria, we hope to reduce the number of cancellations due to preanalytical handling errors and prevent redundant phlebotomy for patients.

A-097 Body Fluid Validation for 11 Analytes on a Chemistry Analyzer

Abstract Background Most clinical chemistry assays are intended for use in serum, plasma, urine, and/or CSF with no performance characteristics on body fluids. However, testing of body fluids can be medically necessary for certain diagnoses. Such as determining the cause of fluid buildup in peritoneal spaces, pleural effusions, whether effusions are transudates or exudates, and even diagnosing some joint disorders. To provide these medically necessary tests, the burden is on the laboratory to perform regulatory-required validations. Herein is the validation of 11 clinical chemistry analytes in several common body fluids. Methods Mixing and stability studies were performed for the following analytes on the Roche cobas c702 (Roche Diagnostics), using the methods intended for use with serum/plasma samples: Albumin, Amylase, Bilirubin, Urea Nitrogen, Cholesterol, Creatinine, Glucose, Lactate Dehydrogenase, Lipase, Protein, and Triglycerides. Six individual fluid samples were mixed with the intended use matrix in 3 ratios: 1:3, 1:1, and 3:1. The following matrices were evaluated: pleural, peritoneal, JP drainage, synovial, and pancreatic cyst fluids. Stabilities were tested for 7 days at room temperature (RT) and 2-8°C. A maximum dilution study was also performed for Amylase. Results Mixing Study: The results are shown in the table below: Stability: For most body fluids, analytes were stable for 7 days at RT and 2-8 °C. The following analytes displayed shorter stability at RT: Bilirubin (peritoneal: 2 days, pleural: 1 day, JP drainage: 1 day), Urea Nitrogen (JP drain fluid: 2 days), Lipase (peritoneal fluid 5 days), and Triglycerides (peritoneal fluid: 5 days). Lactate dehydrogenase in pleural fluid showed a stability of 5 days at RT and 2 days at 2-8 °C. Maximum Dilution A 1:505 compounded manual and automated dilution displayed a &amp;lt;7% bias. Conclusions No sample matrix interferences were observed for any of the body fluids-analyte pairs tested allowing for this medically necessary testing.

A-308 Placental Growth Factor Kryptor Immunoassay Reveals Quality Control Imprecision and Drift

Abstract Background The utility and value of determining the soluble fms-like tyrosine kinase-1 to placental growth factor (sFlt-1/PlGF) ratio for predicting the likelihood of progression to pre-eclampsia in pregnant women admitted with hypertension are increasingly becoming widely recognized. A key finding of the multi-center PRAECIS trial (NEJM Evid 2022;1(12)) is the observation that sFlt-1/PlGF ratios ≥ 40 correlate with higher risk for adverse maternal outcomes. The sFlt-1 and PlGF immunoassays performed on the ThermoFisher Scientific B·R·A·H·M·S Kryptor autoanalyzer became the first FDA-approved tests in 2023 for determining sFlt-1/PlGF ratio. In this study, an evaluation of the analytical performance of the sFlt-1 and PlGF KRYPTOR immunoassays was performed, which included analyte measuring range (AMR), accuracy, precision, and stability studies. Methods Calibration and QC materials (consisting of lyophilized recombinant human proteins), test reagents and solutions, and consumables were purchased and provided by ThermoFisher Scientific. Analytical runs were performed according to vendor’s instructions by trained medical laboratory scientists. Between-day precision of our two instruments for both immunoassays was assessed by assaying all three levels of sFlt-1 and PlGF QC materials, as well as patient serum pools with low PlGF concentration, once to twice daily for multiple consecutive days. Results While the analytical performance of the sFlt-1 immunoassay was robust and performed according to expectation (within-day CV &amp;lt;1% and between-day CV &amp;lt;3%), the PlGF immunoassay was surprisingly less reliable. Imprecision and inaccuracy of the PlGF immunoassay at the low end of its analytical measurement range was reflected by both sporadically out-of-control between-day measurements of all three QC levels (with target ranges of 24 - 36 pg/mL, 80 - 120 pg/mL, and 320 - 480 pg/mL), as well as slow downward drifts of particularly the low level QC material. In one instance, a downtrend was observed from 28 pg/mL to 14 pg/mL over 6 days, even with fresh reagents, solutions, and calibration. Such shortened stability of the PlGF assay does not meet the vendor’s claims of calibration stability of 15 days and onboard kit stability of 29 days. Using vendor’s provided material, the AMR of both sFlt-1 and PlGF were adequately verified and showed excellent linearity (r2&amp;gt; 0.99). Conclusions Despite low level QC imprecision and drift, the sFlt-1/PlGF ratios determined using the B·R·A·H·M·S Kryptor analyzers are acceptable for clinical use but with the caveat that we will perform batch testing with bracketing QCs and conduct stringent QC monitoring, frequent calibrations, and reduce the onboard kit stability as defined by ThermoFisher Scientific. Our findings serve as a reminder that FDA approval does not preclude thorough verification studies of any assay prior to implementation for clinical use.

A-319 Capillary Blood Collection for Egg-cellent Reproductive Insights

Abstract Background In the United States, an estimated 13% of women between the ages of 15 and 49 years, experience impaired reproductive potential (fecundity). Assessment of fecundity typically requires an in-person physician visit and venous blood collection to evaluate hormone levels and identify potential reproductive health conditions. Exploring less invasive, at-home sampling options could offer couples insights into their personal reproductive abilities, providing peace of mind and aiding in family planning. Methods Capillary blood, obtained using the Tasso®+ capillary blood collection device coupled with a BD Microtainer® serum tube, was utilized for measurements of analytes associated with female fecundity (follicle stimulating hormone, luteinizing hormone, estradiol, progesterone, anti-Müllerian hormone, and prolactin). These are all FDA-approved assays measured on Roche cobas® e801, assay parameters remained unchanged. Professional and self-collected capillary serum samples were acquired in parallel with the standard venous serum samples, to compare clinical equivalency of the capillary sampling option. In addition to isothermal stability studies at room temperature (20-25°C) and refrigerated (2-8°C) conditions, shipping excursion studies based on ISTA 7D recommendations were performed using a novel packaging solution to control sample temperature and thus, specimen integrity. Studies to assess matrix equivalency, linearity, and imprecision of this alternate sample type were also performed to demonstrate analytical performance. Results Method comparison of venous and professional collection of capillary samples demonstrated correlations (R) ≥ 0.9720 with slopes ranging from 0.919 to 0.971 and mean biases within ±8.2% for all analytes (n = 19-79). Self-collected capillary serum samples demonstrated correlations (R) ≥ 0.9827 with slopes that ranged from 0.841 to 0.985 and mean biases within ±10.7% (n = 16-26). Isothermal stability was demonstrated for each analyte up to 7 days at room temperature and refrigerated conditions. Simulated shipping excursion results were found to be acceptable for both winter and summer conditions with mean biases for each analyte within ±10.2% and ±19.2%, respectively. Matrix equivalency, linearity, and imprecision results adhered to current CLIA acceptance limits for each respective measurement. Conclusions The analytical and stability results affirm the feasibility of collecting capillary serum in a patient-centric manner, providing women with relevant information about their reproductive health.

A-284 Development of a Low Positive Molecular Control for Mycoplasma genitalium and Trichomonas vaginalis Screening

Abstract Background Mycoplasma genitalium (MG) is a sexually transmitted gram -negative bacteria that infects the urinary and genital tracts. Trichomonas vaginalis (TV) is a protozoan parasite and is the most common curable sexually transmitted infection (STI) worldwide. TV/ MG infections often go unrecognized because infected individuals are either asymptomatic or have symptoms similar to other infections of the urogenital tract (cervicitis in females and urethritis in males). Left untreated, TV/MG can lead to severe health complications including pelvic inflammatory disease, adverse pregnancy outcomes such as preterm delivery and miscarriage, increased risk of HIV acquisition, sexually acquired reactive arthritis, and infertility. The rates of STIs are increasing and differentiating among different STIs is critical to ensure patients receive effective treatment. Amplified nucleic acid based tests (NAATs) have emerged as the gold standard for diagnosis of TV/MG infections due to their high sensitivity and high throughput using a variety of clinical samples including male and female urine. This study describes work to develop a low positive quality control material in human urine for TV/MG amplified nucleic acids tests. Methods A method was developed to eliminate residual enzymatic activity from raw, pooled human urine from both genders to create a homogeneous diluent that supports analyte stability. The urine diluent was tested for viral pathogens (HIV-1, HCV, HBV) and ensure urine proteins and chemistry analytes were within acceptable limits. TaqMan® assays for TV (targeting RNA polymerase Rpb1 gene) and MG (targeting SMC Chromosome segregation gene) were developed and qualified for digital PCR quantitation of these organisms using the BioRad QX200 system. Cultured Trichomonas vaginalis strain C-1:NIH and Mycoplasma genitalium strain G37 were spiked into the urine diluent along with 0.09% sodium azide as a preservative. The concentration of TV and MG was guided by digital PCR quantitation throughout formulation and the final product was tested on Abbott Alinity m STI Panel, Hologic Aptima® Mycoplasma genitalium Assay, and Hologic Aptima® Trichomonas vaginalis Assay. Results Three independent lots were produced that were each detected for both TV and MG on the Abbott Alinity m STI panel. The concentration of the controls targeted a cycle number (CN) of ∼27 for TV and ∼32 for MG and were within acceptable limits. The lots were also positive for TV and MG when tested on the Hologic Aptima TV and MG assays. Accelerated stability studies showed that the product is stable throughout 2 years of shelf life when stored frozen at -20 °C, but is also stable for up to 30 days at 2-8 °C refrigerated storage. Conclusions LGC Clinical Diagnostics is developing a stable, whole organism molecular control material for use with in vitro diagnostic test methods that detect TV and MG. The product will fulfill an unmet need for molecular quality controls for STI testing that are formulated in a true patient-like matrix like urine. This study helps ensure the molecular control will be a low positive on leading diagnostic assays, be consistent batch to batch, and have the needed stability to meet the needs of clinical testing labs.

A-095 A New CO2 Assay with Concentrated Reagent Having Superior Onboard Stability on Mindray BS-2800M Analyzer

Abstract Background Measurement of total content of CO2 in serum or plasma can be used to assist in the diagnosis of various acid-base disorders. There are small amounts (about 0.04%) CO2 in the earth’s atmosphere, or more in an enclosed clinical laboratory space. The environmental CO2 could be dissolved into the CO2 reagent continuously, in particular at lowered temperature when it is opened and stored on the system, which leads an impact on CO2 assay performance. Presently, competitors mainly use additional inserts or with small opening of the reagent container to reduce the contact with air from reagent, to improve its onboard stability. Here, we designed a new CO2 assay by optimizing the reagent formulation with a new protection mechanism to reduce the amount of CO2 absorption to the reagent and improved its onboard stability. This study evaluated performances of the new CO2 assay on Mindray BS-2800M analyzer. Methods Mindray CO2 assay with concentrated reagent is based on PEPC (Phosphoenolpyruvate Carboxylase) enzymatic method. It is designed with an innovative mechanism of reagent formulations with a protective layer of chemical(s) on top of the reagent that prevents CO2 from entering the reagent and reduced its impact to its on-board stability. The onboard stability was conducted with a constant reagent consumption mode to simulate as it in clinical lab use. The onboard study used two levels of Quality Control materials and serum pools. According to CLSI protocols, the following assay performances were evaluated: onboard stability, precision, method comparison, linearity, and interference. Results On Mindray BS-2800M analyzer, Mindray CO2 assay demonstrated an excellent onboard stability. With uncapped reagent on the system, the stability is for 21 days without recalibration, with less than ± 5% deviation from day zero. In parallel onboard stability studies, with Roche CO2 reagent on Cobas c701 system, the relative deviation from day zero was found to be within ±10%; and other three manufacturers` results with deviation exceeded ±10% vs. day zero in 7 days. The linearity of Mindray CO2 assay was determined as from 2.0 to 50.0 mmol/L. Our CO2 assay correlated well with Roche CO2 on Cobas c701 (Mindray = 1.0032 * Roche - 0.0186, r≥0.99). The repeatability and with-lab CVs were ranged from 0.64% to 3.41%, respectively. There was no significant interference (&amp;lt;±10%), at CO2 concentration of 15 mmol/L with bilirubin up to 60 mg/dL,hemolysate up to 800 mg/dL, Intralipid up to 1000 mg/dL, triglycerides up to 1000 mg/dL. Conclusions On Mindray BS-2800M analyzer, the new CO2 assay demonstrated a good ability against environmental CO2 inference in 21 days of onboard time. The new CO2 assay also shown good performances in precision, correlation (accuracy) and anti-interference from endogenous substances. Therefore, we conclude that the new Mindray CO2 assay is suitable for routine clinical laboratory use.

A-087 Stability of fecal calprotectin extracted with BÜHLMANN CALEX® Cap

Abstract Background Calprotectin, a granulocyte-derived alarmin protein, is an established noninvasive biomarker of intestinal mucosal inflammation. Fecal calprotectin testing has become the gold standard for diagnosis of inflammatory bowel diseases. The aim of this work was to determine the stability of calprotectin in stool extracts prepared with the BÜHLMANN CALEX® Cap stool preparation device. Methods The analyte stability study was carried out using CALEX® Cap extracts of human fecal left-over samples. Extraction was performed for 24 hours at room temperature and samples were aliquoted and frozen at &amp;lt; -20°C. The baseline calprotectin concentration was measured from thawed aliquots, which were moved to target storage temperatures (2-8 °C, 18 °C, 28 °C, and 37 °C) for up to 22 days. Five stool samples covering the measuring range of the assay were analyzed with the BÜHLMANN fCAL® turbo in four replicates. Stability evaluations were performed according to CLSI guideline EP25-A1 and EP25Ed2. Results CALEX® Cap derived extracts stored refrigerated at 2-8°C for up to 20 days and at room temperature (18-28°C) for up to 6 days demonstrated deviations from baseline of less than 20%. CALEX® Cap derived extracts stored up to 15 days at 2-8°C and up to 2 days at room temperature (18-28°C) demonstrated deviations from baseline of less than 10%. Conclusions CALEX® Cap provides a stool collection method that stabilizes fecal calprotectin concentrations for an increased processing window. This allows significant timely separation between stool collection and the actual measurement of calprotectin. This specimen stabilization provides for accurate measurements for days after sample collection and thus allows for flexibility for diagnostic laboratories.

B-102 The Impact of Protein / Protein Interactions on Serum Free Light Chain Assay Calibration

Abstract Background Since 2001, Serum Free Light Chain measurements have become established as routine clinical laboratory tests. Katzmann (2002) published a reference interval based on 282 normal samples establishing a ratio reference range 0.26-1.65. Whilst kappa and lambda measurements are of little diagnostic value, kappa/lambda ratio gives a strong indication of monoclonal gammopathy. In recent years, it has been suggested that the ratio may have changed. Here we present investigations identifying protein/protein interactions that may account for the discrepancies between QC release and real-world data; identifying a remediation step which will allow verification of the published ratio. Methods The manufacturers QC release data was reviewed for kappa, lambda and kappa/lambda ratio for all lots from 2018-2023, and compared to published data. To mimic field observation, an accelerated stability study was performed on standard calibrators and protein/protein interactions identified using western blot. Subsequently, calibrators were depleted of alpha-1 antitrypsin (A1AT) and other serum proteins using specific affinity chromatography; accelerated stability was repeated. A calibrator of pure polyclonal free light chains (FLC) in human serum albumin was produced in the presence/absence of A1AT and additional interfering serum proteins. Results At release, the average kappa reference range was 7.2-29.5 mg/L (62 kits, 9 different US blood donor sera collections and 3852 data points) and 7.7-24 mg/L for lambda (78 kits, 9 different US blood donor sera and 4664 data points), with a kappa/lambda ratio of 0.45-1.69. There was minimal change over 5yrs to these measurements. Analysis of FLC calibrators during an accelerated stability identified interactions between kappa FLC and ubiquitous serum proteins, including A1AT. The standard calibrator activity declined by 14.9±0.1% (mean±SEM) over a 4-month accelerated period @22oC, equivalent to 16 months real time. Calibrators depleted of A1AT and specific additional serum proteins showed significantly less decline in activity 1.4±1.4%, p&amp;lt;0.001. When blood donor sera were analysed using the standard calibrators following 4 months at 22oC, the results showed an increase in the reported kappa concentrations compared to those generated from frozen calibrators (19.0[15.4-22.5] to 21.3[17.0-26.0] mg/L, 12.5±3.8%, p&amp;lt;0.001). This observation was mirrored in kappa/lambda ratio (1.3[1.1-1.5] to 1.4[1.2-1.7] mg/L, 12.5±3.8%, p&amp;lt;0.001) and when clinical patient samples were assessed (30.1[14.0-47.1] to 34.3[15.5-56.9] mg/L, 13.8±1.4%, p&amp;lt;0.001). The depleted calibrator did not report an increase in sample results. FLC+HSA calibrators, when spiked with either physiological concentrations of A1AT or other serum proteins, showed a 16.7% and 15.3% decrease in activity respectively, compared to FLC+HSA calibrators without additional proteins. Conclusions At release, US blood donor sera have different absolute kappa mg/L compared to the published reference interval, but these changes do not invalidate the published kappa/lambda ratio, in contrast to recent reports and have not changed since 2018. An unpredictable kappa/protein interaction was observed, particularly with A1AT in a time dependent fashion, which correlated to a reduction in calibrator activity. Removal of A1AT and other specific serum proteins remediated the issue, and the kappa/lambda ratio was verified irrespective of the age of the calibrator.

A structural, magnetic and colloidal stability study of uncoated and silica coated iron oxide samples prepared in two different surfactants

The discovery of new magnetic materials of interest in the biomedicine field is a relevant topic in current research. For years, our research group has been investigating the obtaining and study of nanostructured magnetic samples that behave superparamagnetically to enable their transport in living organisms. We present here a study that summarizes the structural characteristics, magnetic behavior and stability of two Fe3O4 samples synthesized by coprecipitation that were dispersed using two different surfactants (oleylamine, OL, and oleic acid, OA), and two others prepared from the previous ones by reaction with tetraethyl orthosilicate (TEOS). The relationships between the surfactant used in the synthesis, the presence of a certain maghemite (γ-Fe2O3) content, the influence of silica shell thickness and magnetic behaviour of all samples were systematically studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), Mössbauer spectroscopy and H vs. M loops. Rietveld refinements of the XRD profiles confirmed a partial oxidation of the non-silica-coated samples and FTIR spectra of the uncoated samples showed a very strong broad metal-oxygen band and additional sets of bands from the different organic chains of the two surfactants. Individual particles with a mean diameter of 7 and 9 nm were distinguished in TEM images of uncoated magnetic samples. Mössbauer data indicated the presence of non-stoichiometric magnetite in all samples, in agreement with XRD refinements. Magnetic measurements confirmed the superparamagnetic behavior of all the samples. Highest negative zeta potential values are found for the silica covered samples in both acidic and basic medium, being Fe3O4-AO@SiO2 the best suited for the purposes of its dispersibility in future applications. Low polydispersity index (PDI) values confirmed the best stability and dispersibility of all samples investigated in tetrahydrofuran (THF).

Ruthenium(II) complexes containing PEGylated N-heterocyclic carbene ligands for tunning biocompatibility in the fight against cancer

A synthetic procedure was designed for the preparation and characterization of Ag and Ru complexes containing NHC ligands functionalized with PEG fragments. Stability studies were conducted to gain insight of the species in water and other solvents like DMSO, or with reagents like imidazole as representative group for histidine amino acid. The presence of Cl atoms instead of H in the 4,5 positions of the N-heterocyclic carbene afforded higher water stability. The complexes containing PEG units must be considered inactive as anticancer agents. To enhance the anticancer activity of PEG-containing complexes, the balance between hydrophilicity and hydrophobicity was adjusted using a silane moiety, and an anionic carbosilane dendrimer as a lipophilic carrier.