Note 7 - Stockholders' Equity (Details Textual) - USD ($) | Jul. 24, 2019 | Jul. 16, 2019 | Jun. 19, 2019 | Apr. 26, 2019 | Feb. 26, 2019 | Feb. 25, 2019 | Feb. 18, 2019 | Jul. 31, 2019 | Feb. 28, 2019 | Sep. 30, 2018 | Mar. 31, 2018 | May 31, 2017 | Feb. 28, 2019 | Dec. 31, 2019 | Dec. 31, 2018 |
Preferred Stock, Shares Authorized | | | | | | | | | | | | | | 10,000,000 | 10,000,000 |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | | | | $ 0.01 | $ 0.01 |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | | | | 2,486 | 3,450 |
Conversion of Stock, Shares Issued | | | | | | | | | | | | | | 296,390 | 95 |
Stock Issued During Period, Shares, Issued for Services | | | | | | | | | | | | | | 3,224 | 17 |
Stock Issued During Period, Value, Issued for Services | | | | | | | | | | | | | | $ 24,000 | $ 513,500 |
Stock Issued During Period, Value Expensed During the Period, Issued for Services | | | | | | | | | | | | | | | 314,419 |
Prepaid Expense, Value of Stock Issued for Services During Period | | | | | | | | | | | | | | $ 199,080 | |
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent | | | | | | | | | | | | | | 110.00% | |
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period | | | | | | | | | | | | | | 10 years | |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period | | | | | | | | | | | | | | 3 years | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | | | | | | | | | | | | | | 0 | |
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | | | | | | | | | | | | | | $ 99,975 | |
Series I Warrants [Member] | | | | | | | | | | | | | | | |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | | | | | | | | | | | | | | 48 | |
Class of Warrant or Right, Exercise Price of Warrants or Rights | | | | | | | | | | | | | | $ 15,000 | |
Share-based Payment Arrangement, Option [Member] | | | | | | | | | | | | | | | |
Share-based Payment Arrangement, Expense | | | | | | | | | | | | | | $ 104,420 | 155,304 |
Share-based Payment Arrangement, Option [Member] | Research and Development Expense [Member] | | | | | | | | | | | | | | | |
Share-based Payment Arrangement, Expense | | | | | | | | | | | | | | 43,801 | 41,998 |
Share-based Payment Arrangement, Option [Member] | General and Administrative Expense [Member] | | | | | | | | | | | | | | | |
Share-based Payment Arrangement, Expense | | | | | | | | | | | | | | $ 60,619 | $ 113,306 |
Series G Convertible Preferred Stock and Related Warrants [Member] | | | | | | | | | | | | | | | |
Convertible Preferred Stock and Related Warrants, Authorized | | | | | | 1,000 | | | | | | | | | |
Proceeds from Issuance of Convertible Preferred Stock and Related Warrants, Maximum | | | $ 500,000 | $ 500,000 | $ 250,000 | $ 1,000,000 | | | | | | | | | |
Convertible Preferred Stock and Related Warrants Issued | | | 500 | 500 | 500 | | | | | | | | | | |
Series I Convertible Preferred Stock [Member] | | | | | | | | | | | | | | | |
Convertible Preferred Stock and Related Warrants Issued | | | 500 | | | | | | | | | | | | |
Conversion of Series C Preferred Stock Into Common Stock [Member] | | | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | | | | | 587 | | 420 |
Conversion of Stock, Shares Issued | | | | | | | | | | | | | 39 | | 28 |
Conversion of Series C Preferred Stock Into Series F Preferred Stock [Member] | | | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | 1,563 | | | | | | |
Conversion of Series D Preferred Stock Into Common Stock [Member] | | | | | | | | | | | | | | | |
Conversion of Stock, Shares Issued | | | | | | | | | | | | | | | 67 |
Conversion of Series E Preferred Stock Into Series F Preferred Stock [Member] | | | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | 1,200 | | | | | | |
Conversion of Series F Preferred Stock Into Common Stock [Member] | | | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | | | | | | 507 | |
Conversion of Stock, Shares Issued | | | | | | | | | | | | | | 191 | |
Conversion from Series F Preferred Stock to Series H Preferred Stock [Member] | | | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | 2,256 | | | | | | | |
Conversion of Series H Preferred Stock Into Common Stock [Member] | | | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | | | | | | 1,570 | |
Conversion of Stock, Shares Issued | | | | | | | | | | | | | | 296,160 | |
Conversion of Series I Preferred Stock [Member] | | | | | | | | | | | | | | | |
Conversion of Stock, Shares Converted | | | | | | | | | | | | | | 0 | |
Series B Convertible Preferred Stock [Member] | | | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | | | | $ 1,000 | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | | | | 100 | 100 |
Convertible Preferred Stock, Conversion Price1 | | | | | | | | | | | | | | $ 350,000 | |
Series D Convertible Preferred Stock [Member] | | | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | | $ 1,000 | | | |
Stock Issued During Period, Shares, New Issues | | | | | | | | | | | | 1,000 | | | |
Proceeds From Issuance Of Convertible Preferred Stock, Net of Issuance Cost | | | | | | | | | | | | $ 980,000 | | | |
Series E Convertible Preferred Stock [Member] | | | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | $ 1,000 | | | $ 1,000 | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | | | | | 1,200 |
Stock Issued During Period, Shares, New Issues | | | | | | | | | | 600 | 600 | | | | |
Proceeds From Issuance Of Convertible Preferred Stock, Net of Issuance Cost | | | | | | | | | | $ 600,000 | $ 590,000 | | | | |
Series F Convertible Preferred Stock [Member] | | | | | | | | | | | | | | | |
Number of Series C and Series E Preferred Stock Exchanged for Series F Convertible Preferred Stock | | | | | | | 2,763 | | | | | | | | |
Series G Convertible Preferred Stock [Member] | | | | | | | | | | | | | | | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | 1,000 | | | | | | | |
Series H Convertible Preferred Stock [Member] | | | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | | | | $ 1,000 | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | | | | 1,686 | |
Convertible Preferred Stock, Conversion Price1 | | $ 15,000 | | | | | | | | | | | | | |
Conversion of Stock, Shares Issued | | 3,257 | | | | | | | | | | | | | |
Series I Convertible Preferred Stock [Member] | | | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | | | | $ 1,000 | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | | | | 700 | |
Convertible Preferred Stock, Conversion Price1 | $ 15,000 | | | | | | | | | | | | | | |
Stock Issued During Period, Shares, New Issues | 700 | | | | | | | | | | | | | | |
Proceeds from Issuance of Preferred Stock and Preference Stock | $ 700,000 | | | | | | | | | | | | | | |
Series C Convertible Preferred Stock [Member] | | | | | | | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share | | | | | | | | | | | | | | $ 1,000 | |
Preferred Stock, Shares Outstanding, Ending Balance | | | | | | | | | | | | | | | 2,150 |