Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities:
Net loss	$ (8,290)	$ (8,792)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of property and equipment	458	332
Amortization and abandonment of patent and trademark rights	79	276
Redeemable warrants valuation adjustment	0	(1)
Equity-based compensation	111	198
Change in assets and liabilities:
Inventories	(1,009)	0
Prepaid expenses and other current assets	61	112
Accounts payable	189	238
Accrued expenses	(836)	1,431
Net cash used in operating activities	(9,237)	(6,206)
Cash flows from investing activities:
Purchase of property, equipment and construction in progress	(240)	(266)
Additions to patent and trademark rights	(169)	(120)
Deposits on capital leases refunded	0	2
Sales and maturities of short-term and long-term marketable securities	54	(36)
Net cash used in investing activities	(355)	(420)
Cash flows from financing activities:
Payments on capital leases	(15)	(18)
Proceeds from sale of stock, net of issuance costs	9,293	8,458
Net cash provided by financing activities	9,278	8,440
Net (decrease) increase in cash and cash equivalents	(314)	1,814
Cash and cash equivalents at beginning of period	2,156	803
Cash and cash equivalents at end of period	1,842	2,617
Supplemental disclosures of non-cash investing and financing cash flow information:
Issuance of common stock for accounts payable	672	38
Unrealized (loss) gain on marketable securities	(26)	168
Supplemental disclosure of cash flow information:
Cash paid for interest expense	$ (2)	$ (9)