3 4 dihydroxy l phenylalanine l dopa

All chemicals used were of analytical grade
and used as received without any further purification. All solutions
were prepared with deionized water of resistivity not less than 18.2
MΩ cm. Hexaamineruthenium(III) chloride (RuHex), 3,4-dihydroxy-l-phenylalanine (L-DOPA), and sodium hydroxide were purchased
from Merck (Gillingham, U.K.). Potassium chloride was purchased from
Fisher Scientific (Loughborough, U.K.).
The commercial conductive
PLA/carbon black (PLA/CB) filament was purchased from Farnell (Leeds,
U.K.). Note that we have utilized this filament in a different system
and more details of its physiochemical characterized can be found
in ref (18 (link)). Raise3D
premium PLA filament and Raise3D premium ABS filament were purchased
from Create Education (Chorley, U.K.). Flexible motor cage was printed
from RS PRO 1.75 mm natural FLEX 45 purchased from RS (Corby, U.K.).
2 mm nitrile rubber O-ring stock, 5 mm i.d., 11 mm o.d. flanged ball
bearings, 5 mm brass rod, M2.5 × 12 screws, M3 × 3 grub
screws, M3 × 10 screws, banana jack socket for potentiostat connection,
Arduino Nano development board, 2.1 mm barrel jack, and 200k trim
potentiometer were purchased from RS (Corby, U.K.). The 12 V 10k rpm
DC motor with encoder, carbon brushes, L298N module H bridge motor
driver board, and SSD1306 128 × 64 OLED display were purchased
from Amazon.

A375 (ATCC CRL-1619) human malignant melanoma, SH-4 (ATCC CRL-7724) human melanoma, and B16-F10 (ATCC CRL-6475) murine melanoma cell lines were purchased from LGC Standards (Łomianki, Poland). Immortalized human keratinocytes HaCaT were purchased from CLS Cell Lines Service GmbH (Eppelheim, Germany). Fetal bovine serum (FBS) was obtained from Pan-Biotech (Aidenbach, Germany). Dulbecco’s modified Eagle’s medium (DMEM)/high glucose, with and without phenol red, Dulbecco’s phosphate buffered saline (DPBS), mushroom tyrosinase from Agaricus bisporus, L-tyrosine, 3,4-dihydroxy-l-phenylalanine (L-DOPA), 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2′,7′-dichlorofluorescin diacetate (H₂DCFDA), N-acetylcysteine (NAC), N-Succinyl-Ala-Ala-Ala-p-nitroanilide (SANA), kojic acid (≥99.0%), chlorogenic acid (≥95%), ellagic acid (≥95%), gallic acid (97.5–102.5%), kaempferol (≥97.0%), quercetin (≥95.0%), rutin (≥94.0%), 1,10-phenantroline (≥99.0%), and neutral red solution (3.3 g/L) were purchased from Merck (Darmstadt, Germany). Water (H₂O), formic acid (HCOOH), and acetonitrile (CH₃CN) for HPLC analysis were purchased from J.T. Baker (Witko, Łódź, Poland).

Aluminum chloride hexahydrate, sodium carbonate, sodium hydroxide, hydrochloric acid, acetone, methanol, were purchased from Avantor Performance Materials Poland S.A. (Gliwice, Poland). The Folin-Ciocalteu′s phenol reagent was from Merck (Darmstadt, Germany). DMEM and antibiotics were purchased from Biowest (Nuaillé, France), FBS was obtained from EURx (Gdansk, Poland). Chitosan medium molecular weight, CS MMW (200–800 cP, 1 wt. % in 1% acetic acid) was supplied by Sigma-Aldrich (Poznan, Poland) as well as all the other chemicals (2,2-Diphenyl-1-picrylhydrazyl (DPPH), sodium chloride, bovine serum, hexadecyltrimethylammonium bromide (CTAB), hyaluronic acid (HA), phosphate buffer), tyrosinase, 3,4-Dihydroxy-L-phenylalanine (L-DOPA), quercetin, gallic acid.