Morphological Changes in Astrocytes by Self-Oxidation of Dopamine to Polydopamine and Quantification of Dopamine through Multivariate Regression Analysis of Polydopamine Images

Abstract

Astrocytes, also known as astroglia, are important cells for the structural support of neurons as well as for biochemical balance in the central nervous system (CNS). In this study, the polymerization of dopamine (DA) to polydopamine (PDA) and its effect on astrocytes was investigated. The polymerization of DA, being directly proportional to the DA concentration, raises the prospect of detecting DA concentration from PDA optically using image-processing techniques. It was found here that DA, a naturally occurring neurotransmitter, significantly altered astrocyte cell number, morphology, and metabolism, compared to astrocytes in the absence of DA. Along with these effects on astrocytes, the polymerization of DA to PDA was tracked optically in the same cell culture wells. This polymerization process led to a unique methodology based on multivariate regression analysis that quantified the concentration of DA from optical images of astrocyte cell culture media. Therefore, this developed methodology, combined with conventional imaging equipment, could be used in place of high-end and expensive analytical chemistry instruments, such as spectrophotometry, mass spectrometry, and fluorescence techniques, for quantification of the concentration of DA after polymerization to PDA under in vitro and potentially in vivo conditions.

Artificial Melanogenesis by Confining Melanin/Polydopamine Production inside Polymersomes

“…As the concentration of L-DOPA/dopamine encapsulated in our melanin-and PDA-based melanosome mimics was in the lower range of standard concentrations (25 × 10 −6 -100 × 10 −3 м) reported for the formation of Melanin and PDA nanoparticles, [45,46] we induced self-assembly of high concentrations of polymer (10 mg mL −1 ) to obtain concentrated polymersome solutions (around 2 × 10 12 vesicles mL −1 ) that demonstrate light-absorption properties (Table S4: Supporting Information and Figure 3). Furthermore, PDMS-b-PMOXA polymersomes are known to be impermeable to small molecules but allow diffusion of molecular oxygen.…”

Dopamine-Modified Hyaluronic Acid (DA-HA) As A Novel Dopamine-Mimetics With Minimal Autoxidation And Cytotoxicity

“…For measuring the autoxidation of DA and DA-HA, absorbance wavelength at 405 nm was used 51 . For optimizing the visualization condition, 100 µM DA was added to HEPES, ACSF, and neurobasal media and measured the autoxidation using a microplate reader (GloMax explorer multimode, Promega).…”

“…On one hand, when DA enters the cell inside via monoamine transporters, DA is degraded by monoamine oxidases and induces cytotoxicity by a formation of radicals through unpaired electrons of generated superoxide 11 . On the other hand, DA is oxidized to generate external free radicals through extracellular oxidation and causes cytotoxicity on diverse cell types such as mesencephalic neurons 12,13 , cortical neurons 14 , and astrocytes 15 , implying that external oxidation of DA induces non-speci c cell death. However, it still remains unclear which of the two proposed mechanisms, intracellular or extracellular ROS, is the major cause of DA-induced cytotoxicity.…”

“…External free radicals are generated through a process called autoxidation, a self-oxidation without cells in an aqueous solution 16 . Autoxidation of DA can be easily measured by optical density (OD) at wavelengths ranging from 350 to 450 nm 15 . Interestingly, it has been reported that DA-induced cortical neuronal cell death is accelerated with nomifensine, a monoamine transporter inhibitor 14 .…”

Dopamine-Modified Hyaluronic Acid (DA-HA) As A Novel Dopamine-Mimetics With Minimal Autoxidation And Cytotoxicity

“…On one hand, when DA enters the cell inside via monoamine transporters, DA is degraded by monoamine oxidases and induces cytotoxicity by a formation of radicals through unpaired electrons of generated superoxide 11 . On the other hand, DA is oxidized to generate external free radicals through extracellular oxidation and causes cytotoxicity on diverse cell types such as mesencephalic neurons 12,13 , cortical neurons 14 , and astrocytes 15 , implying that external oxidation of DA induces non-specific cell death. However, it still remains unclear which of the two proposed mechanisms, intracellular or extracellular ROS, is the major cause of DA-induced cytotoxicity.…”