10. Debt Issuance Costs

In connection with the issuance of notes payable, TransEnterix Surgical incurred debt acquisition costs in the amount of $109,133 and $43,853 during the years ended December 31, 2011 and 2012, respectively. TransEnterix Surgical capitalizes these costs and is amortizing them over the life of the debt, using the straight-line method of amortization which approximates the effective-interest method. Amortization expense for the debt issuance costs was $65,318 and $28,285 for the years ended December 31, 2013 and 2012, respectively.

In January 2012, TransEnterix Surgical recorded $63,030 of debt issuance costs related to the issuance to the lenders of warrants to purchase Series B-1 Convertible Redeemable Preferred Stock. The preferred stock warrants were issued in conjunction with a promissory note issued to the lenders. At that time, TransEnterix Surgical began amortizing the debt issuance costs over the four year term of the promissory note resulting in $15,921 and $10,539 of interest expense for the years ended December 31, 2013 and 2012, respectively.

In December 2012, TransEnterix Surgical recorded $65,455 of debt issuance costs related to the issuance of warrants to purchase Series B-1 Convertible Redeemable Preferred Stock to lenders. The preferred stock warrants were issued in conjunction with a promissory note issued to the lender. At that time, TransEnterix Surgical began amortizing the debt issuance costs over the three year term of the promissory note resulting in $21,601 and $592 of interest expense for the year ended December 31, 2013 and 2012, respectively.

Total amortization expense related to issuance of warrants was $37,522 and $39,416 for the years ended December 31, 2013 and 2012, respectively. Total accumulated amortization for the warrant issuance costs was $76,938 and $39,416 at December 31, 2013 and 2012, respectively. Debt issuance costs, net of amortization, are recorded within other assets on the consolidated balance sheets.