Stock-based Compensation (Details - Share-based compensation) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 111	$ 186
Research and Development Expense [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	63	56
General and Administrative Expense [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 48	$ 130