Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (15,292,000)	$ (34,453,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,933,000	2,038,000
Warrant liability revaluation income	(11,884,000)	(2,929,000)
Derivative liability revaluation expense	462,000	0
Loss on disposal or impairment of property and equipment	69,000	56,000
Depreciation and amortization	564,000	767,000
Intangible asset impairment	3,905,000	0
Recovery of doubtful accounts	(12,000)	(5,000)
Loss on write-down of inventory	356,000	0
Decrease (increase) in operating assets:
Accounts receivable	12,000	9,000
Inventory	126,000	89,000
Prepaid expenses and other current assets	796,000	35,000
Other assets	(65,000)	0
Increase (decrease) in operating liabilities:
Accounts payable	(139,000)	(114,000)
Related party payable	(9,778,000)	9,719,000
Accrued expenses and deferred rent	(214,000)	641,000
Accrued interest payable	228,000	0
Deferred revenue	(457,000)	41,000
Net cash used in operating activities	(29,390,000)	(24,106,000)
Cash flows from investing activities:
Purchase of property and equipment	(253,000)	(271,000)
Proceeds from the sale of property and equipment	1,000	26,000
Net cash used in investing activities	(252,000)	(245,000)
Cash flows from financing activities:
Proceeds from private placement, net	17,933,000	0
Proceeds from common stock offering, net	0	15,872,000
Payment of deferred offering costs	(42,000)	0
Proceeds from the exercise of stock options	0	255,000
Principal payments on capital lease obligations	(2,000)	(3,000)
Net cash provided by financing activities	17,889,000	16,124,000
Net decrease in cash and cash equivalents	(11,753,000)	(8,227,000)
Cash and cash equivalents, beginning of period	29,268,000	37,495,000
Cash and cash equivalents, end of period	17,515,000	29,268,000
Noncash Investing and Financing Items [Abstract]
Property and equipment in accounts payable	57,000	11,000
Deferred offering costs in accounts payable	23,000	0
Reduction of warrant liability upon cashless exercise of warrants	$ 0	$ 82,000