An injection catheter system comprising: (a) an actuator; (b) an outer needle (120, 320, 820) comprising a sharp tip and a tubular body defining a lumen, the outer needle (120, 320, 820) extending distally from the actuator; and (c) an inner needle (110, 310, 410, 510) at least partially disposed within the lumen and extending distally from the actuator, the inner needle (110, 310, 410, 510) having a distal tip (128, 628) configured such that at least a portion of the distal tip (128, 628) has a surface contour with an interstitial cavity adapted to receive a therapeutic gel (130, 730, 915); wherein the system is configured such that (a) in a first position, the distal tip (128, 628) is fully disposed within the lumen to temporarily retain the therapeutic gel (130, 730, 915) in the interstitial cavity and (b) in a second position, the outer needle (120, 320, 820) is retracted proximally, exposing the interstitial cavity to deliver the therapeutic gel (130, 730, 915) to a target area in a body; wherein the actuator is adapted to proximally or distally translate the outer needle (120, 320, 820) such that translation of the outer needle (120, 320, 820) is independent of translation of the inner needle (110, 310, 410, 510); and wherein the inner needle (110, 310, 410, 510) comprises a tubular body defining an inner lumen, the inner lumen adapted to receive a guide wire. (a) an actuator; (b) an outer needle (120, 320, 820) comprising a sharp tip and a tubular body defining a lumen, the outer needle (120, 320, 820) extending distally from the actuator; and (c) an inner needle (110, 310, 410, 510) at least partially disposed within the lumen and extending distally from the actuator, the inner needle (110, 310, 410, 510) having a distal tip (128, 628) configured such that at least a portion of the distal tip (128, 628) has a surface contour with an interstitial cavity adapted to receive a therapeutic gel (130, 730, 915); wherein the system is configured such that (a) in a first position, the distal tip (128, 628) is fully disposed within the lumen to temporarily retain the therapeutic gel (130, 730, 915) in the interstitial cavity and (b) in a second position, the outer needle (120, 320, 820) is retracted proximally, exposing the interstitial cavity to deliver the therapeutic gel (130, 730, 915) to a target area in a body; wherein the actuator is adapted to proximally or distally translate the outer needle (120, 320, 820) such that translation of the outer needle (120, 320, 820) is independent of translation of the inner needle (110, 310, 410, 510); and wherein the inner needle (110, 310, 410, 510) comprises a tubular body defining an inner lumen, the inner lumen adapted to receive a guide wire. wherein the system is configured such that (a) in a first position, the distal tip (128, 628) is fully disposed within the lumen to temporarily retain the therapeutic gel (130, 730, 915) in the interstitial cavity and (b) in a second position, the outer needle (120, 320, 820) is retracted proximally, exposing the interstitial cavity to deliver the therapeutic gel (130, 730, 915) to a target area in a body; wherein the actuator is adapted to proximally or distally translate the outer needle (120, 320, 820) such that translation of the outer needle (120, 320, 820) is independent of translation of the inner needle (110, 310, 410, 510); and wherein the inner needle (110, 310, 410, 510) comprises a tubular body defining an inner lumen, the inner lumen adapted to receive a guide wire.