Income taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Deferred Tax Assets and Liabilities

The Company’s deferred tax assets and liabilities as of December 31, 2018 and 2017 are as follows:

	December 31,
	2018			2017
Deferred tax assets:
NOL carryforward	$	49,480,731		$	46,326,407
R&E credit carryforward		2,559,479			2,559,479
Share-based compensation		329,796			345,088
Inventory reserve		19,068			45,338
Depreciation		—			71,756
Interest expense		51,152			—
Accruals and other		284,662			247,093
Total deferred tax assets		52,724,888			49,595,161
Valuation allowance		(52,348,036	)		(49,251,408	)
Deferred tax liabilities:
Intangible assets		(256,011	)		(343,753	)
Depreciation		(120,841	)		—
Net	$	—		$	—

Expected Income Tax Provision (Benefit) from Applying Federal Statutory Tax Rates to the Pre-Tax Loss and Actual Income Tax Provision (Benefit)

The difference between the Company’s expected income tax provision (benefit) from applying federal statutory tax rates to the pre-tax loss and actual income tax provision (benefit) relates to the effect of the following:

	2018			2017
Federal income tax benefit at statutory rates		21.0	%		34.0	%
Permanent adjustment		(1.4	)%		—
Provision to return adjustment		(0.2	)%		—
State income tax benefit, net of Federal benefit		(6.4	)%		6.8	%
Tax reform impact		—			(134.5	)%
Change in valuation allowance		(13.0	)%		93.0	%
Change in state tax rates and other		—			0.7	%
		0.0	%		0.0	%