Alb, albumin; Albumin-binding peptide SA21; Boc, tert-butyloxycarbonyl; DCM, dichloromethane; DIEA, N,N-diisopropylethylamine; DMEM, Dulbecco's Modified Eagle Medium; DMF, dimethylformamide; DMSO, dimethyl sulfoxide; DOI, desoctapeptide (B23−30) insulin; Diabetes mellitus; EDT, 1,2-ethanedithiol; FBS, fetal bovine serum; Fmoc, 9-fluorenylmethoxycarbonyl; HATU, 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxid hexafluorophosphate; HBTU, O-(benxontriazol-1-yl)-1,1,3,3-tetramethyluronium; HPLC, high performance liquid chromatography; HTRF, homogeneous time resolved fluorescence; IR-B, human insulin receptor isoform B; ITT, insulin tolerance test; Insulin synthesis; LC‒MS, liquid chromatography mass spectrometry; Long-acting insulin; Mtt, 4-methyltrityl; NBD-X, 6-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoic acid; STZ, streptozotocin; Sortase A (SrtA) ligation; SrtA, sortase A; THF, triflouroacetic acid; TIS, triisoproylsilane; i.p., intraperitoneal; pAkt, phosphorylated protein kinase B; t-Bu, tert-butyl