Note 8 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Total stock-based compensation expense	$ 121,371	$ 278,131
Research and Development Expense [Member]
Total stock-based compensation expense	12,011	58,892
General and Administrative Expense [Member]
Total stock-based compensation expense	$ 109,360	$ 219,239