Total share-based compensation expense (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Total share-based compensation expense:
Research and development expense	$ 87,780	$ 142,147	$ 198,826	$ 142,147
Selling, general and administrative expense	85,353	44,916	441,158	54,666
Total share-based compensation	$ 173,133	$ 187,063	$ 552,204	$ 196,813