Note 11 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforward	$ 16,681,908	$ 16,273,259
Research and development tax credit carryforward	1,063,877	949,340
Stock-based compensation expense	1,808,509	1,709,867
Accrued salaries and directors’ fees	317,246	185,961
Depreciation	8,414	5,532
Total deferred tax assets	19,879,954	19,123,959
Deferred tax liabilities
Net deferred tax assets	19,879,954	19,123,959
Valuation allowance	(19,879,954)	(19,123,959)
Net deferred tax asset after reduction for valuation allowance	$ 0	$ 0