Note 8 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Stock-based compensation expense	$ 278,131	$ 181,280
Research and Development Expense [Member]
Stock-based compensation expense	58,892	33,000
General and Administrative Expense [Member]
Stock-based compensation expense	$ 219,239	$ 148,280