(483h) Dopamine Particles with Precise Size As Drug Delivery Material Afford Great Potential in the Treatment of Neurological Diseases

Dopamine (DA), 3,4-dihydroxy phenethylamine is a neurotransmitter in the brain that is responsible for many functions via dopamine pathways entailing both physiological and behavioral processes i.e., movements, function, cognition, motivation, reward, and so on. DP within the brain is synthesized in the nerve terminal from the amino acid tyrosine that is brought in by crossing blood-brain barriers. In the treatment of neurological diseases, DP plays significant roles due to its diverse biological functions. Therefore, materials capable of releasing DP in a controllable and timely manner confer great advantages in the treatment of neurological disorders. Here, polydopamine (p(DA)) particles were synthesized in a special medium via self-crosslinking of DP at monodisperse and precisely controlled particle sizes, about 120 nm, 180 nm, 290 nm, 380 nm, 520 nm, and 780 nm without using any crosslinker. The SEM images of p(DA) particles revealed perfectly spherical particles with smooth surfaces. The isoelectric points (IEP) of monodisperse p(DP) of 180 and 780 nm were measured at pH 3.5±0.02 and 3.7±0.02, respectively. The zeta potential of p(DP) particles at about neural pH, 7.4 was measured in -43.5±2.5 to -56.7±3.4 mV range depending on the particle size confirming their stable nature in aquatic environments. The p(DA) particles were shown a pH-dependent swellings behavior e.g., at pH 2 p(DA) particles swelled to a size of 1214±37 from 180 nm and to 1598±176 nm from 780 nm, respectively. Also, p(DA) particles were determined to be hydrolytically long-term degradable e.g., about 22.1±2.5% degradation was determined for all the p(DP) particles irrespective of their sizes in 10 days. Furthermore, p(DA) particles were found as blood compatible with 1.4±0.2% hemolysis via hemolysis assay and found not to affect the blood clotting mechanism with 98±1.1% blood clotting indices via blood clotting assay up to 2.0 mg/mL concentration. The antioxidant tests via total phenol content (TPC) and Trolox equivalent antioxidant capacity (TEAC) assays of p(DA) particles (at 180 nm) revealed antioxidant activity of 56.6±14.0 µg/mL and 1.08±0.02 mM Trolox equivalent/g. Moreover, the DP release profile of p(DA) particles loaded with DP via two methods i) from the corresponding DP solution in ethanol, and ii) by supercritical carbon dioxide (ScCO₂) impregnation method were compared to improve and control the DP release time and amounts, precisely.