Note 12 - Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Notes Tables

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]

January 1,	Number of shares
2012		2,502
2013		2,871
2014		4,128
2015		5,463
2016		7,257
2017		12,623
2018		106,076
2019		233,862
Total additional shares		374,782

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Three Months Ended March 31,
	2019		2018
General and administrative	$	224,676	$	166,701
Research and development		51,157		48,438
Total stock compensation Expense	$	275,833	$	215,139

	Period Ended March 31, 2019
General and administrative	$	1,074,183
Research and development		667,736
Total stock compensation expense	$	1,741,919

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Number of Underlying Shares		Weighted- Average Exercise Price Per Share		Weighted- Average Contractual Life Remaining in Years		Aggregate Intrinsic Value
Outstanding as of January 1, 2019		783,383	$	12.14
Granted
Forfeited
Expired
Outstanding as of March 31, 2019		783,383		12.14		8.92	$	695,400
Exercisable as of March 31, 2019		434,515		19.38		8.84	$	374,063
Vested and expected to vest		783,383	$	12.14		8.92	$	695,400

Liability Options [Member]

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	January 13,
	2019
Risk free interest rate		2.53	%
Expected term (in years)		4.50-5.00
Stock price	$	1.36
Dividend yield			%
Expected volatility		121.0-123.0	%