Property and equipment (Tables)

12 Months Ended

Dec. 31, 2015

Property and equipment

Schedule of property and equipment, net

	Estimated
	useful life			As of December 31,
	(in years)			2015		2014
Equipment	2	-	7	$	958,175	$	945,116
Computer hardware	3	-	5		3,266,233		2,963,629
Furniture and fixtures	5	-	7		192,565		194,399
Leasehold improvements	3	-	10		746,336		749,275
Total property and equipment, gross					5,163,309		4,852,419
Less: Accumulated depreciation and amortization					(3,351,690)		(2,712,672)
Property and equipment, net				$	1,811,619	$	2,139,747

Schedule of property and equipment depreciation and amortization expense

	Year ended December 31,
	2015			2014		2013
Depreciation and amortization expense		$	664,303	$	621,695	$	554,765