Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (9,813)	$ (8,259)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of property and equipment	856	948
Fair value of convertible note adjustment	582
Amortization of debt issue costs	263	37
Amortization and abandonment of patent and trademark rights	22	63
Redeemable warrants valuation adjustment	(1,165)	(2,417)
Equity-based compensation	929	571
Realized gain (loss) on securities	(14)	(17)
Gain on sale of building	(223)
Changes in assets and liabilities:
Prepaid expenses and other assets	(251)	(13)
Accounts receivable	(1,070)	(24)
Accounts payable	166	566
Accrued expenses	(922)	604
Net cash used in operating activities	(10,640)	(7,941)
Cash flows from investing activities:
Purchases of property and equipment	(51)	(20)
Additions to patent and trademark rights	(76)	(49)
Proceeds from sale of building	1,050
Sales and maturities of short-term marketable securities	(831)	2,799
Net cash provided by investing activities	92	2,730
Cash flows from financing activities:
Proceeds from sale of common stock, net of issuance costs	5,070	2,417
Proceeds for lease financing obligation	4,080
Financing obligation payment	(264)
Debt issuance costs	(439)	(102)
Proceeds from note payable	3,059	1,900
Payoff of mortgage note payable	(1,957)
Security deposits paid	(114)
Net cash provided by financing activities	9,435	4,215
Net decrease in cash and cash equivalents	(1,113)	(996)
Cash and cash equivalents at beginning of year	1,412	2,408
Cash and cash equivalents at end of year	299	1,412
Supplemental disclosures of non-cash investing and financing cash flow information:
Issuance of common stock for accounts payable and accrued expenses	330	898
Unrealized (loss) gain on marketable securities	(14)	16
Fair value of redeemable warrants granted	1,265	2,050
Supplemental disclosure of cash flow information:
Cash paid for interest expense	$ 328	$ 101