This study was designed to load different antibodies (Abs) and a fluorescent dye onto the red blood cell (RBC) surface. We have used fluorescein isothiocyanate (FITC)-conjugate anti-human Ab, CD22-PE (B-cell marker-phycoerythrin Ab), and 4′,6-diamidino-2-phenylindole (DAPI) for insertion over the RBC surface. In a first step, conjugation experiments were performed: in dimethyl sulfoxide (DMSO), RBCs were conserved and modified by succinic anhydride to create an additional -COOH group, and then activated with 3-(3-dimethylaminopropyl)carbodiimide-N-hydroxysuccinimide (EDC-NHS) in 2-(N-morpholino) ethanesulfonic acid hydrate buffer for insertion of labeled Abs or DAPI. In a second step, fluorescence signals were evaluated by microscopy and the mean fluorescence intensities of cell lysates were measured by spectrofluorometry. The results showed clear evidence for adsorption of FITC- and PE-labeled Abs to activated conserved RBCs. DAPI was adsorbed well also to DMSO-conserved RBCs without the need for an activation step. The DMSO conservation step was enough to create reactive RBCs for insertion of specific Abs and fluorescent dyes. The additional modification by succinic anhydride and activation with EDC-NHS resulted in two- to seven-fold increase in fluorescence signals, indicating a much higher RBC loading capacity. These Ab- and fluorescent dye-functionalized RBCs have potentially high application in developing new biomedical diagnostic and in vitro assay techniques.

Aims:: We aim to evaluate the potential application of amine reactive fluorogenic reagents for estimating enzymatic proteolysis.Background:: Proteolytic enzymes play important roles in regulating many physiological processes in living organisms.Objectives:: Assessment of protein degradation by using reagents for protein assay techniques.Methods:: We have assayed samples at the start and after 30-60 minutes incubation with trypsin by Chromeo P503 (Py 1 pyrylium compound) and CBQCA (3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde) as amine reactive reagents and NanoOrange as non-amine reactive dye.Results:: All BSA prepared samples with trypsin have shown significantly higher fluorescence intensity (FI) versus controls (which reflects proteolysis) when assayed by Chromeo P503 (Py 1 pyrylium compound) and CBQCA (3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde) as amine reactive reagents. However, same samples assayed with NanoOrange as non-amine reactive reagent did not show any significant variation between samples containing trypsin and controls.Conclusion:: These results are confirming reliability of highly sensitive protein assays utilizing amine reactive fluorogenic reagents for general estimation of proteolysis.

Purpose: To investigate the contractile responses of vascular smooth muscle cells (VSMCs) to spasmogens after incubation with harmaline, harmine, and harmalol, which are alkaloids obtained from Peganum harmala L., a member of the Zygophyllaceae family. Methods: Contractile responses of VSMCs to norepinephrine (NE; 1 µmol/L) and potassium chloride (KCl; 60 mmol/L) were recorded in rat aortic ring preparations pre-incubated with 0.5, 1, 5 and 10 µmol/L of each alkaloid for 15 min. Responses were expressed as mean values of contractions in incubated preparations, relative to the recorded tension prior to treatment with alkaloids. Results: Pre- incubation with harmaline at concentration of 10 µmol/L significantly reduced contractile responses to NE by 69.0 ± 3.0 % (p < 0.00002), and decreased KCl-induced contraction by 34.0 ± 9.0 % (p < 0.05). Harmalol was the most effective in inhibiting contractions to KCl (48.0 ± 9.0 %, p < 0.01). However, harmalol produced relatively moderate inhibitory effects on NE-induced contractions (46.0 ± 4.0 %, p < 0.005), followed by harmine (52.0 ± 8.0 %, p < 0.02), but it did not significantly affect contractile responses to KCl. Conclusion: These results highlight the differential effects of pre-incubation with alkaloids from P. harmala and their potential effects on the prevention of VSMC spasms induced by either chemicals or stimuli that change the membrane potential.

Backgrounds: Various physiological functions and reaction cascades, as well as disease progression in the living systems, are controlled by the activity of specific proteolytic enzymes. We conducted the study to evaluate protease activity by assessing peptide fragments from either conserved or labeled red blood cells (RBCs) with aminofluorescein (AF) in the reaction media.Methods: RBCs were incubated in media containing trypsin. Subsequently, the concentration of peptide fragments in the reaction media, resulted by the digestion with trypsin from conserved cells, was estimated by 3‐(4‐carboxybenzoyl)quinoline‐2‐carboxaldehyde (CBQCA) as an amine‐reactive fluorogenic reagent. In a second approach, we conjugated AF to the conserved RBCs and then exposed AF‐labeled RBCs to trypsin. This was followed by directly measuring the fluorescence intensity (FI) in the reaction media to estimate the concentration of AF‐labeled peptide fragments resulting from the enzyme’s activity.Results: Show a concentration‐ and time‐dependent increase in FIs, reflecting the activity of trypsin as a proteolytic enzyme. The FIs increased significantly by 4 to 5 folds in samples treated with different enzyme concentrations, and by over 11 folds after 2 h incubation in media containing a 50 μL trypsin, as evidenced by CBQCA assays.Conclusion: These fast and affordable approaches could be applied with high reliability for the general estimation of protease activity in samples and customized for diagnostic purposes and prognostic evaluation in various diseases.