In March 2014, the Company entered into securities purchase agreements for the private placement of (i) 12% second-priority secured non-convertible promissory notes maturing in 2019 (the “2014 Secured Notes”) and (ii) warrants to purchase 0.3 share of the Company’s common stock for each dollar in principal amount of the 2014 Secured Notes sold by the Company. Pursuant to those securities purchase agreements, the Company sold 2014 Secured Notes in a total aggregate principal amount of $3,725,000, together with warrants to purchase up to 1,117,500 shares of common stock, for aggregate gross proceeds of $3,725,000, before placement agent commissions and other expenses.

The 2014 Secured Notes have a five-year maturity, and they bear interest at a rate of 12% per year, payable semi-annually, in arrears, on each six-month and one-year anniversary of the issuance date. The 2014 Secured Notes are not convertible into shares of the Company’s common stock. Following the third anniversary of the issuance date, the 2014 Secured Notes may be prepaid, without penalty or premium, provided that all principal and unpaid accrued interest under all 2014 Secured Notes is prepaid at the same time. Prior to the third anniversary of the issuance date, the Company may prepay all, but not less than all, of the principal and unpaid accrued interest under the 2014 Secured Notes at any time, subject to the Company’s payment of the additional prepayment premium stated in the notes. The 2014 Secured Notes are secured by a security interest in the Company’s property and assets, which security interest is junior and subordinate to the security interest that secures the senior secured note payable previously issued by the Company to Brainlab AG.

The warrants issued to the investors are exercisable, in full or in part, at any time prior to the fifth anniversary of the issuance date, at an exercise price of $1.75 per share, subject to adjustment from time to time for stock splits or combinations, stock dividends, stock distributions, recapitalizations and other similar transactions. Assumptions used in calculating the fair value of the warrants using the Black-Scholes valuation model were:

The Company allocated the $3,725,000 in proceeds proportionately between the 2014 Secured Notes and the warrants issued to investors based on their relative fair values, with $413,057 being recorded as equity. The 2014 Secured Notes were recorded at the principal amount less a discount equal to the $413,057 amount recorded as equity. This discount is being amortized to interest expense over the five year term of the notes using the effective interest method.

Non-employee directors of the Company invested a total of $1,100,000, either directly or through a trust. The Company’s placement agents earned cash commissions of $145,500 as well as warrants to purchase 72,750 shares of the Company’s common stock. The placement agent warrants have the same terms and conditions as the investor warrants. The placement agent cash commissions, the $30,210 fair value of the placement agent warrants, and other offering expenses totaling $76,186 were recorded as deferred financing costs and are classified as other assets. These deferred financing costs are being amortized to interest expense over the term of the 2014 Secured Notes using the effective interest method.