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Stock Option Plans and Warrants to Purchase Common Stock (Tables)
12 Months Ended
Dec. 31, 2021
Grant 2015 Plan  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Schedule of shares available for grant under the 2015 plan

Shares available for grant at January 1, 2021

    

214,689

Options granted

 

(452,189)

Options forfeited

 

207,246

Options exercised

30,254

Shares available for grant at December 31, 2021

 

Stock options  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Schedule of activity under the 2005 plan and the 2015 plan

    

    

    

Weighted

Average

Exercise

    

Options

    

Price

Balance outstanding at December 31, 2019

 

1,506,972

$

3.77

Granted

 

520,812

 

2.17

Forfeited

 

(88,222)

 

13.06

Exercised

(5,758)

1.19

Balance outstanding at December 31, 2020

 

1,933,804

$

2.96

Granted

 

452,189

 

0.91

Forfeited

 

(239,914)

 

3.65

Exercised

 

(30,254)

 

0.85

Balance outstanding at December 31, 2021

 

2,115,825

$

2.48

Schedule of weighted-average exercise price, by price range, for outstanding options to purchase common stock

    

Weighted

    

    

    

    

Average

Remaining

Contractual

Outstanding

Exercisable

Price Range

    

Life in Years

    

Options

    

Options

$0.71-$3.00

 

7.97

 

1,941,203

 

1,373,724

$6.40-$15.60

 

3.13

 

129,310

 

129,310

$20.10-$22.60

 

2.00

 

45,312

 

45,312

Total

 

7.55

 

2,115,825

 

1,548,346

Share-based Payment Arrangement  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Schedule of share-based compensation expense

Share-based compensation

    

2021

    

2020

Research and development

$

158,478

$

195,560

General and administrative

 

203,081

 

214,373

Total

$

361,559

$

409,933

Warrants  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Schedule of warrant activity

    

    

    

Weighted

Average

Exercise

    

Warrants

    

Price

Balance at December 31, 2019

 

6,192,711

$

2.88

Granted

 

 

Exercised

 

(461,234)

 

1.87

Expired

 

 

Balance at December 31, 2020

 

5,731,477

$

2.96

Granted

 

 

Exercised

 

(20)

 

3.95

Expired

 

(2,403,385)

 

3.95

Balance at December 31, 2021

3,328,072

$

2.25

Schedule of remaining life, by grant date, for outstanding warrants

    

    

    

Remaining

    

    

    

    

Exercise

Contractual

Outstanding

Exercisable

Grant Date

    

Price

    

Life in Years

    

Warrants

    

Warrants

11/1/2017

$

2.50

 

0.83

 

49,872

 

49,872

3/29/2018

$

1.95

 

1.24

 

10,000

 

10,000

7/2/2018

$

2.25

 

0.01

 

3,268,200

 

3,268,200

Total

 

3,328,072

 

3,328,072