Condensed Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net loss	$ (5,816,274)	$ (7,026,424)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	296,045	357,023
Accretion of discount on NuvoGen obligation	50,124	52,082
Provision for excess inventory	192,427	30,542
Amortization of Growth Term Loan discount and issuance costs	122,583	102,979
Stock-based compensation expense	396,646	170,048
Employee stock purchase plan expense	14,888
Accretion of incentive from landlord	(35,500)	(23,666)
Accrued interest on available-for-sale securities investments	(5,573)	(7,288)
Changes in operating assets and liabilities:
Accounts receivable	181,312	141,680
Inventory	63,198	(195,203)
Prepaid expenses and other	64,765	119,538
Deferred offering costs	10,830
Accounts payable	311,036	714,361
Accrued liabilities	(388,339)	(537,061)
Deferred revenue	(93,874)	(22,028)
Net cash used in operating activities	(4,635,706)	(6,123,417)
Investing activities
Purchase of property and equipment	(65,385)	(220,570)
Sales, redemptions and maturities of available-for-sale securities	1,700,000	3,000,000
Net cash provided by investing activities	1,634,615	2,779,430
Financing activities
Proceeds from Growth Term Loan		5,000,000
Payments on Growth Term Loan	1,546,612
Payments on capital leases	27,199	27,300
Proceeds from exercise of stock options	35,023
Payments on NuvoGen obligation	200,000
Net cash provided by (used in) financing activities	(1,738,788)	4,972,700
Increase (decrease) in cash and cash equivalents	(4,739,879)	1,628,713
Cash and cash equivalents at beginning of period	7,507,659	3,293,983
Cash and cash equivalents at end of period	2,767,780	4,922,696
Noncash investing and financing activities
Allocation of term loan B warrant discount		122,460
Fixed asset purchases payable and accrued at period end	44,256	1,030,174
Deferred offering costs payable and accrued at period end	76,262
Stock issued for settlement of accrued bonus		(364,910)
Purchase of property and equipment under capital lease		176,360
Incentive from landlord		710,000
Retirement of treasury stock	75,000
Supplemental cash flow information
Cash paid for interest	$ 225,713	$ 237,397