Characterization of structural changes occurring in insulin at different time intervals at room temperature by surface-enhanced Raman spectroscopy

• Published in: Photodiagnosis and photodynamic therapy 2023-12, Vol.44, p.103796-103796, Article 103796
• Main Authors: Meraj, Lubna, Mehmood, Nasir, Majeed, Muhammad Irfan, Nawaz, Haq, Rashid, Nosheen, Fatima, Rida, Habiba, Umm e, Tahseen, Hira, Naz, Maira, Asghar, Maria, Ghafoor, Nida, Ahmad, Hafsa
• Format: Article
• Language: English
• Subjects: Insulin; Partial least square regression analysis; Principal component analysis; Silver nanoparticles; Surface-enhanced Raman spectroscopy
• ISSN: 1572-1000; 1873-1597
• DOI: 10.1016/j.pdpdt.2023.103796

•Room temperature stability of insulin pharmaceutical is investigated after regular intervals of time by employing SERS.•Raman spectral signal is enhanced by using silver nanoparticles (Ag-NPs) as SERS active substrate.•Spectra of all samples of insulin are compared to differentiate the structural changes in protein/API after regular intervals of time.•Time varied SERS spectral data of all insulin samples is qualitatively discriminated by PCA.•PLSR analysis model is found useful in the quantitative investigation of SERS qualitative findings with 0.98 coefficient of determination. Insulin storage above the temperature recommended by food and drug administration (FDA) causes decrease in its functional efficacy due to degradation and aggregation of its protein based active pharmaceutical ingredient (API) that results poor glycemic control in diabetic patients. The aggregation of protein causes serious neurodegenerative diseases such as type-2 diabetes, Huntington disease, Parkinson's disease, and Alzheimer's disease. Surface-enhanced Raman spectroscopy (SERS) has been employed for the denaturation study of many proteins at the temperature above the recommendations of food and drug administration (FDA) (above 30 °C) which indicates potential of technique for such studies. SERS along with multivariate discriminating analysis techniques-based analysis of degradation of liquid pharmaceutical insulin protein after regular intervals of time at room temperature to analyze the structural changes in this protein during the storage of insulin pharmaceutical at room temperature. Silver nanoparticles (Ag-NPs) prepared by chemical reduction method are used as SERS active substrate for the surface enhancement of the insulin spectral signal. SERS spectral measurements of insulin were collected from eight different samples of insulin in the time range of 7 pm to 7 am first at fridge temperature (5 °C), second after half hour and next six with the time difference of 2 h each time at room temperature. The acquired SERS spectral data was preprocessed and analyzed. SERS structural transformations detection and discrimination potential in insulin was further confirmed by applying multivariate discriminating analysis techniques including principal component analysis (PCA) and Partial least square regression analysis (PLSR). SERS significantly detects the structural changes produced in insulin even after 2 h of insulin placement at room temperature. PCA successfully differentiates