Background: Resorbable electrospun polycaprolactone (PCL) scaffolds for tissue reconstruction can provide physicians with an "off the shelf" product tailored to the patient's specific tissue architecture. However, many tissue-engineering platforms do not possess the necessary long-term mechanical stability needed to properly support tissue development. Objective: Sintering has been explored as a means of altering the properties of electrospun PCL. However, crystallinity-driven changes in mechanical properties following thermal treatment have not been previously investigated. Methods: PCL nanofibers were produced by electrospinning and subsequently thermally sintered (at 55, 56 and 58 degrees C) to enhance their long-term mechanical integrity in response to representative biological milieux. Results: Scaffolds initially sintered at 56 degrees C displayed 6-fold increases in compressive strength and 3-fold increases in modulus, while displaying 10-fold increases in energy dissipation with increasing sintering temperature. Sintering just below the T-m resulted in amorphization of the 55 degrees C sample as indicated by the 20-fold lower XRD peak intensities. Although crystallinity is suppressed, the polymer chains likely retain chain alignment from electrospirMing and are apparently highly susceptible to recrystallization. After only 1 d PBS exposure, the 55 degrees C samples recover a substantial fraction of the as-spun crystallinity; 7 d of exposure fully restores as-spun peak intensities. The mechanical properties of all three (55, 56, or 58 degrees C) scaffolds displayed peak values of compressive strength and modulus following 7 d exposure. Conclusion: In contrast with the current state-of-the-art which assumes that tissue engineering scaffolds only grow weaker following exposure, in these scaffolds maximum values of compressive strength and modulus were observed after 7 d of aqueous immersion. This suggests that polymeric recrystallization can be used to increase or optimize mechanical properties in vitro/in vivo. Scaffolds that increase their mechanical integrity during biological exposures constitute a new pathway enabling clinical advances. (C) 2013 Elsevier Ltd. All rights reserved.