An investigation into the acidity-induced insulin agglomeration: implications for drug delivery and translation

Insulin undergoes agglomeration with (subtle) changes in its biochemical environment, including acidity, application of heat, ionic imbalance, and exposure to hydrophobic surfaces. The therapeutic impact of such unwarranted insulin agglomeration is unclear and needs further evaluation. A systematic investigation was conducted on recombinant human insulin-with or without labeling with fluorescein isothiocyanate-while preparing insulin suspensions (0.125, 0.25, and 0.5 mg/mL) at pH 3. The suspensions were incubated (37 °C) and analyzed at different time points (t = 2, 4, 24, 48, and 72 h). Transmission electron microscopy and nanoparticle tracking analysis identified colloidally stable (zeta potential 15 ± 5 mV) spherical agglomerates of unlabeled insulin (100-500 nm). Circular dichroism established the preservation of insulin's secondary structure rich in α-helices despite exposure to an acidic environment (pH 3) for 72 h. Furthermore, fluorescence lifetime imaging microscopy illustrated an acidic core inside these spherical agglomerates, while the acidity gradually lessened toward the periphery. Some of these smaller agglomerates fused to form larger chunks with discrete zones of acidity. The data indicated a primary nucleation-driven mechanism of acid-induced insulin agglomeration under physiologically relevant conditions. </p

Discovery and Structural Elucidation of Novel Microcystins Using MS and MSn with Python Code

Microcystins (MCs) are cyclic heptapeptide hepatotoxins with a vast structural diversity (\u3e300 congeners). However, many more congeners are theoretically possible, and a workflow was developed for putative identification of novel MCs using liquid chromatography (LC) coupled to high-resolution mass spectrometry (HRMS) and MSn with Python code. Water samples collected from Lake Erie were sonicated and filtered, and solid-phase extraction was performed. A portion of the water sample was reacted with mercaptoethanol using the method developed by Miles et al. for structural elucidation. Extracted MCs were analyzed using UHPLC coupled to an Orbitrap Fusion instrument for HRMS. Collision-induced dissociation (CID) and higher-energy CID (HCD) were used for MSn analyses. A total of 33 MCs were found in lake water samples, including two unknown MCs. Two Python codes were developed to elucidate the structures of MCs. Code 1 was written to generate a list of masses of theoretically possible MC congeners. Code 2 was written to compare the experimentally obtained masses of MC fragment ions to the theoretical fragment masses. Using Codes 1 and 2, the two unknown MCs with m/z values of 526.7980 (z=+2) and 1025.5302 (z=+1) were putatively identified as MC-HarR and MC-E(OMe)R, respectively

Colloidal Nanoribbons: From Infrared to Visible

Using the cation-exchange method, colloidal PbS nanoribbons are converted completely into CdS nanoribbons. This process expands the emission spectrum of the nanoribbons from infrared to visible. The morphology of nanoribbons remains the same after cation exchange, but the crystal structure changes from rock salt to zincblende. CdS nanoribbons exhibit blue band-edge photoluminescence under ultraviolet-light excitation. Cathodoluminescence spectroscopy of the CdS nanoribbons shows multicolor (blue, green, and red) emissions. Further time-resolved photoluminescence spectroscopy studies show that the lifetime of the midgap states is more than 2 orders of magnitude longer than that of the band-edge states