Mesenchymal stem cells differentiate to retinal ganglion-like cells in rat glaucoma model induced by polystyrene microspheres

AIM

The study aimed to evaluate the differentiation ability of intravitreally injected rat bone marrow-derived mesenchymal stem cells (rBM-MSCs) to retinal ganglion-like cells in a polystyrene microsphere induced rat glaucoma model.

MATERIALS AND METHODS

The glaucoma rat model was generated via intracameral injection of 7 microliter polystyrene microspheres. Green fluorescence protein-labeled (GFP) rBM-MSCs were transplanted intravitreally at or after induction of ocular hypertension (OHT), depending on the groups. By the end of the fourth week, flat-mount retinal dissection was performed, and labeled against Brn3a, CD90, GFAP, CD11b, Vimentin, and localization of GFP positive rBM-MSCs was used for evaluation through immunofluorescence staining and to count differentiated retinal cells by flow cytometry. From 34 male Wistar albino rats, 56 eyes were investigated.

RESULTS

Flow cytometry revealed significantly increased CD90 and Brn3a positive cells in glaucoma induced and with rBM-MSC injected groups compared to control(P = 0.006 and P = 0.003 respectively), sham-operated (P = 0.007 and P < 0.001 respectively), and only rBM-MSCs injected groups (P = 0.002 and P = 0.009 respectively). Immunofluorescence microscopy revealed differentiation of GFP labeled stem cells to various retinal cells, including ganglion-like cells. rBM-MSCs were observable in ganglion cells, inner and outer nuclear retinal layers in rBM-MSCs injected eyes.

CONCLUSION

Intravitreally transplanted rBM-MSCs differentiated into retinal cells, including ganglion-like cells, which successfully created a glaucoma model damaged with polystyrene microspheres. Promisingly, MSCs may have a role in neuro-protection and neuro-regeneration treatment of glaucoma in the future.

Polystyrene microsphere-mediated optical sensing strategy for ultrasensitive determination of aflatoxin M1 in milk

Aflatoxin M₁ (AFM₁) contamination poses a serious threat to human health globally. Hence, it is necessary to develop reliable and ultrasensitive methods for the determination of AFM₁ residue in food products at low levels. In this study, a novel polystyrene microsphere-mediated optical sensing (PSM-OS) strategy was constructed to solve the problems of low sensitivity and susceptibility to interference from the matrix in AFM₁ determination. Polystyrene (PS) microspheres have the advantages of low cost, high stability, and controllable particle size. They can be useful optical signal probes for qualitative and quantitative analyses attributed to the fact that they have strong ultraviolet-visible (UV-vis) characteristic absorption peaks. Briefly, magnetic nanoparticles were modified with the complex of bovine serum protein and AFM₁ (MNP₁₅₀-BSA-AFM₁), and biotinylated antibodies of AFM₁ (AFM₁-Ab-Bio). Meanwhile, PS microspheres were also functionalized with streptavidin (SA-PS₉₅₀). In the presence of AFM₁, a competitive immune reaction was triggered leading to the changes in AFM₁-Ab-Bio concentrations on the surface of MNP₁₅₀-BSA-AFM₁. The complex of MNP₁₅₀-BSA-AFM₁-Ab-Bio binds with SA-PS₉₅₀ to form the immune complexes due to the special binding of biotin and streptavidin. The remaining SA-PS₉₅₀ in the supernatant was determined by UV-Vis spectrophotometer after magnetic separation, which positively correlated with the concentration of AFM₁. This strategy allows for ultrasensitive determination of AFM₁ with limits of detection as low as 3.2 pg/mL. It was also successfully validated for AFM₁ determination in milk samples, and a high consistency was found with the chemiluminescence immunoassay. Overall, the proposed PSM-OS strategy can be used for the rapid, ultrasensitive, and convenient determination of AFM₁, as well as other biochemical analytes.

A microfluidic colorimetric biosensor for in-field detection of Salmonella in fresh-cut vegetables using thiolated polystyrene microspheres, hose-based microvalve and smartphone imaging APP

A microfluidic colorimetric biosensor was developed using thiolated polystyrene microspheres (SH-PSs) for aggregating of gold nanoparticles (AuNPs), a novel hose-based microvalve for controlling the flow direction, and a smartphone imaging APP for monitoring colorimetric signals. Aptamer-PS-cysteamine conjugates were used as detection probes and reacted with Salmonella in samples. Complementary DNA - magnetic nanoparticle (cDNA - MNP) conjugates were used as capture probes, reacted with the free aptamer-PS-cysteamine conjugates. AuNPs were aggregated on the surface of Salmonella-aptamer-PS-cysteamine conjugates, resulting in a visible color change in the detection chamber, which indicating different concentrations of Salmonella. The limit of detection was low to 6.0 × 10¹ cfu/mL. The microfluidic biosensor exhibited a good specificity. It was evaluated by analyzing salad samples spiked with Salmonella. The recoveries ranged from 91.68% to 113.76%, which indicated its potential application in real samples.

Impact of water chemistry on surface charge and aggregation of polystyrene microspheres suspensions

The discharge of microplastics into aquatic environment poses the potential threat to the hydrocoles and human health. The fate and transport of microplastics in aqueous solutions are significantly influenced by water chemistry. In this study, the effect of water chemistry (i.e., pH, foreign salts and humic acid) on the surface charge and aggregation of polystyrene microsphere in aqueous solutions was conducted by batch, zeta potentials, hydrodynamic diameters, FT-IR and XPS analysis. Compared to Na⁺ and K⁺, the lower negative zeta potentials and larger hydrodynamic diameters of polystyrene microspheres after introduction of Mg²⁺ were observed within a wide range of pH (2.0-11.0) and ionic strength (IS, 0.01-500mmol/L). No effect of Cl^-, HCO₃^- and SO₄^2- on the zeta potentials and hydrodynamic diameters of polystyrene microspheres was observed at low IS concentrations (<5mmol/L), whereas the zeta potentials and hydrodynamic diameters of polystyrene microspheres after addition of SO₄^2- were higher than that of Cl^- and HCO₃^- at high IS concentrations (>10mmol/L). The zeta potentials of polystyrene microspheres after HA addition were decreased at pH2.0-11.0, whereas the lower hydrodynamic diameters were observed at pH<4.0. According to FT-IR and XPS analysis, the change in surface properties of polystyrene microspheres after addition of hydrated Mg²⁺ and HA was attributed to surface electrostatic and/or steric repulsions. These investigations are crucial for understanding the effect of water chemistry on colloidal stability of microplastics in aquatic environment.