Stockholders' equity (Tables)

6 Months Ended

Jun. 30, 2019

Stockholders Equity Note [Abstract]

Schedule of Company Recognized Stock-Based Compensation Expense

For the three and six months ended June 30, 2019 and 2018, the Company recognized stock-based compensation expense as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Cost of services	$	524	$	1,341	$	562	$	3,731
Research and development		18,333		61,080		35,460		130,551
General and administrative		61,365		140,158		137,378		292,340
Sales and marketing		5,749		11,311		10,604		25,458
	$	85,971	$	213,890	$	184,004	$	452,080

Schedule of Warrants to Purchase Shares of Common Stock

At June 30, 2019 and December 31, 2018, the following warrants to purchase shares of common stock were outstanding:

				Outstanding at
Issuance	Exercise Price		Expiration	June 30, 2019		December 31, 2018
November 2009	$	197.75	November 2019		270		270
January 2010	$	197.75	January 2020		270		270
March 2010	$	197.75	March 2020		55		55
November 2011	$	197.75	November 2021		212		212
December 2011	$	197.75	December 2021		27		27
March 2012	$	2,747.50	March 2019		—		165
February 2015	$	165.00	February 2025		9,001		9,001
May 2015	$	165.00	May 2020		138,310		138,310
May 2016	$	32.81	May 2021		189,577		189,577
June 2016	$	32.81	May 2021		82,035		82,035
June 2017	$	19.50	June 2022		18,754		18,754
July 2017	$	17.25	July 2022		6,350		6,350
July 2017	$	12.50	July 2022		50,000		50,000
July 2017	$	10.63	July 2022		1,000,003		1,000,003
February 2018	$	4.06	February 2023		184,615		184,615
February 2018	$	3.25	February 2023		1,846,153		1,846,153
					3,525,632		3,525,797