Stock-based Compensation (Details - Share-based compensation) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 89	$ 103	$ 294	$ 372
Research and Development Expense [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	51	54	163	163
General and Administrative Expense [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 38	$ 49	$ 131	$ 209