License agreements, research collaborations and development agreements (Details Textual)	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) Agreement	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Agreement	Sep. 30, 2017 USD ($)
License Agreements Research Collaborations And Development Agreements [Line Items]
Royalty expense	$ 62,500	$ 62,500	$ 187,500	$ 194,686
Annual future minimum royalty payments due	$ 250,000		$ 250,000
FISH Product Line [Member]
License Agreements Research Collaborations And Development Agreements [Line Items]
Number of license agreements | Agreement	1		1