Determination of human insulin in dog plasma by a selective liquid chromatography-tandem mass spectrometry method: Application to a pharmacokinetic study

Simultaneous separation of insulin and six therapeutic analogues on a mixed mode column: HPLC-UV method development and application

Human insulin and six most used therapeutic analogues are very similar in terms of retention on a reversed-phase column. Thus, the LC methods prescribed in the European Pharmacopoeia monographs for insulin and insulin analogues include many similar separation methods, which tend to be time consuming when separating individual products of insulins or are inadequate when handling a mixture. In this study, we present a simple, robust, versatile and accessible HPLC-UV separation method for identification and quantification of human insulin and its analogues in one run. The simultaneous separation and detection is possible by fine-tuning the mobile phase properties that affect the separation mechanism on a mixed mode column combining anion exchange and reversed-phase characteristics. Also developed was a simple and effective SPE sample cleaning procedure with insulin recoveries ranging from 80 to 100% for all analogues. On the other hand, the concentration of major excipients such as phenol and m-cresol fall below 1%. The two developed and validated separation methods differ in their compatibility with the use of a quaternary or binary pump, thus enabling sample characterisation independent of the HPLC solvent delivery system. The methods are compatible with the use of a mass spectrometric detector for an indisputable identification.

Recent advances in the determination of insulins from biological fluids

The qualitative and quantitative determination of insulin and its related substances (e. g., C-peptide) is of great importance in many different areas of analytical chemistry. In particular, due to the steadily increasing prevalence of metabolic disorders such as diabetes mellitus, an adequate control of the circulating amount of insulin is desirable. In addition, also in forensics and doping control analysis, the determination of insulin in blood, urine or other biological matrices plays a major role. However, in order to establish general reference values for insulin and C-peptide for diabetology, the comparability of measured concentrations is indispensable. This has not yet been fully implemented, although enormous progress has been made in recent years, and the search for a "gold standard" method is still ongoing. In addition to established ligand-binding assays, an increasing number of mass-spectrometric methods have been developed and employed as the to-date available systems (for example, high-resolution/high accuracy mass spectrometers) provide the sensitivity required to determine analyte concentrations in the sub-ng/mL (sub-100pmol/L) level. Meanwhile, also high-throughput measurements have been realized to meet the requirement of testing a high number of samples in a short period of time. Further developments aim at enabling the online measurement of insulin in the blood with the help of an insulin sensor and, in the following, in addition to a brief review, today's state of the art testing developments are summarized.

A highly selective and sensitive detection of insulin with chemiluminescence biosensor based on aptamer and oligonucleotide-AuNPs functionalized nanosilica @ graphene oxide aerogel

A novel, highly selective and sensitive chemiluminescence (CL) biosensor for insulin (INS) detection was proposed based on aptamer and oligonucleotide-gold nanoparticles functionalized nanosilica @ graphene oxide aerogel. Initially, nanosilica functionalized graphene oxide aerogel (SiO₂@GOAG) was successfully prepared and the composite showed rich pore distribution, large specific surface area and good biocompatibility. Insulin aptamer (IGA3) was used as a biorecognition element and oligonucleotide functionalized gold nanoparticles (ssDNA-AuNPs) was used as CL signal amplification materials, which were functionalized on the surface of SiO₂@GOAG. The multi-functionalized composite - ssDNA-AuNPs/IGA3/SiO₂@ GOAG was obtained and used to construct the CL biosensor for insulin detection. When insulin is present in a sample, the insulin will bind to the IGA3, which will result in the release of ssDNA-AuNPs. The released ssDNA-AuNPs would catalyze the luminescence of luminol and H₂O₂. The linear range of the CL biosensor for insulin detection was 7.5 × 10^-12 to 5.0 × 10^-9 moL/L and the detection limit was 1.6 × 10^-12 moL/L (S/N = 3). The selectivity and stability of the CL biosensor were also studied and the results showed that the biosensor exhibited high selectivity and good stability due to the introduction of ssDNA-AuNPs/IGA3/SiO₂@GOAG. The CL biosensor was finally used for recombinant human insulin detection in recombinant human insulin injection and the results were satisfactory.