Property and equipment, net (Details) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 875,555	$ 953,923
Accumulated depreciation	(801,095)	(622,883)
Property and equipment, net	74,460	331,040
Depreciation expense	228,158	324,548	$ 277,231
Property and equipment disposals	28,422
Proceeds from sales of property and equipment	4,805	5,344	$ 5,255
Loss on disposal of property and equipment	23,617
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	421,999	421,999
Computers and computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	275,670	311,847
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	177,886	177,886
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	0	13,368
Capital in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 0	$ 28,823

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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