4. PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2015

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT

Property and equipment consisted of the following at December 31, 2015 and 2014:

Description	Life		2015			2014
Computer equipment		3 years	$	193,596		$	168,209
Office furniture and equipment		5-7 years		247,679			247,679
Software		3 years		125,412			116,022
Laboratory equipment		7 years		1,120,693			1,100,559
Leasehold improvements		5 years		683,295			675,672
Manufacturing equipment		7 years		910,792			889,352
Subtotal				3,281,467			3,197,493
Less: accumulated depreciation				(2,443,600	)		(2,099,389	)
Property and equipment, net			$	837,867		$	1,098,104

Property and equipment is carried at cost less accumulated depreciation. Depreciation is calculated by the straight-line method over the estimated useful life of three to seven years, depending upon the type of equipment, except for leasehold improvements which are amortized using the straight-line method over the remaining lease term or the life of the asset, whichever is shorter. The cost of repairs and maintenance is charged as an expense to the consolidated statements of operations as incurred. Depreciation expense totaled $351,403 and $387,779 for the years ended December 31, 2015 and 2014, respectively.