Assumptions used to value the options granted and warrants issued using the Black-Scholes option pricing model (Details)	Jun. 30, 2016 $ / shares	Dec. 31, 2015 $ / shares
Series E and G
Stock price volatility	111.60%
Risk-free rate of return	4.26%
Annual dividend yield	0.00%
Expected life (in years)	0.5
Series F and H
Stock price volatility	111.60%
Risk-free rate of return	4.26%
Annual dividend yield	0.00%
Expected life (in years)	3.0
Mentor warrants in years	21.96	22.4
Weighted average outstanding warrant exercise price per share	$ 1.9	$ 1.88