Property and equipment (Tables)

12 Months Ended

Dec. 31, 2016

Property and equipment

Schedule of property and equipment, net

	Estimated
	useful life			December 31,
	(in years)			2016		2015
Equipment	2	-	7	$	998,722	$	958,175
Computer hardware	3	-	5		3,637,938		3,266,233
Furniture and fixtures	5	-	7		256,889		192,565
Leasehold improvements	3	-	10		1,037,386		746,336
Total property and equipment, gross					5,930,935		5,163,309
Less: Accumulated depreciation and amortization					(4,256,525)		(3,351,690)
Property and equipment, net				$	1,674,410	$	1,811,619

Schedule of property and equipment depreciation and amortization expense

	Year ended December 31,
	2016			2015		2014
Depreciation and amortization expense		$	927,691	$	664,303	$	621,695