Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net loss	$ (10,310,000)	$ (6,697,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Write-off of inventory	597,000
Depreciation and amortization	39,000	47,000
Change in fair value of convertible preferred stock warrant liability	(250,000)	(274,000)
Change in fair value of maturity date preferred stock warrant liability	(10,000)	(87,000)
Change in fair value of convertible shareholder notes derivative liability	1,224,000	(1,373,000)
Share-based compensation	942,000	283,000
Non-cash interest expense on convertible shareholder notes	1,736,000	1,387,000
Changes in operating assets and liabilities:
Accounts receivable	33,000	65,000
Inventory	27,000	(82,000)
Prepaid expenses and other current assets	(110,000)	(129,000)
Deferred financing costs		48,000
Other assets	(11,000)
Accounts payable	(17,000)	228,000
Accrued liabilities excluding accrued interest on convertible note	226,000	(416,000)
Deferred revenue	32,000
Deferred rent	26,000	(23,000)
Grant liability	304,000
Net cash used in operating activities	(5,522,000)	(7,023,000)
Investing activities:
Purchase of property and equipment		(125,000)
Cash acquired in reverse merger	19,017,000
Payment of transaction costs of reverse merger	(96,000)
Net cash provided by (used in) investing activities	18,921,000	(125,000)
Financing activities:
Proceeds from the exercise of convertible preferred stock warrants		27,000
Proceeds from issuance of convertible notes and warrants	4,374,000	7,435,000
Proceeds from the exercise of stock options	22,000	59,000
Net cash provided by financing activities	4,396,000	7,521,000
Net increase in cash and cash equivalents	17,795,000	373,000
Cash and cash equivalents at beginning of year	3,557,000	3,184,000
Cash and cash equivalents at end of year	21,352,000	3,557,000
Supplemental disclosure for noncash investing and financing activities:
Exchange of convertible preferred stock warrants for common stock	25,000
Conversion of convertible shareholder notes and related interest payable	12,156,000	7,781,000
Reclassification of convertible shareholder notes derivative liability	2,268,000
Conversion of preferred stock	$ 46,030,000