www.advhealthmat.de COMMENT 1700647 (1 of 3) © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Response to “Correspondence Concerning Hemocompatibility of Superhemophobic Titania Surfaces” S. Movafaghi, V. Leszczak, W. Wang, J. A. Sorkin, L. P. Dasi, K. C. Popat,* and A. K. Kota* DOI: 10.1002/adhm.201700647 donor-to-donor variability in the number of platelets and it is not possible to compare the absolute values from differ- ent donors. However, similar trends were observed for blood used from each donor, which implies the reproducibility of the trends observed in our experiments. Most importantly, the blood from each donor clearly indicated that the superhe- mophobic titania nanotube surfaces have significantly lower platelet adhesion and activation (not minor differences) com- pared to the unmodified non-textured titania surfaces (with p < 0.05). 3. As with any biological response, it must always be noted that the choice of material, material properties, platelet density and donor-to-donor variation make a comparison of abso- lute values between studies (e.g., with Polydimethylsiloxane, PDMS) extremely difficult. For example, even within studies conducted on PDMS surfaces, there is a significant variation in the reported platelet adhesion measurements (e.g., some are higher and some are lower compared to the values re- ported in our study). [3–9] This variation could be attributed to the different PDMS compositions and different platelet den- sities employed as well as donor-to-donor variability. Rather than such comparisons of absolute values (which may not be meaningful), the primary focus and novelty of our work is to demonstrate that superhemophobic titania surfaces have significantly lower platelet adhesion and activation compared to non-textured titania surfaces. 4. Regarding the platelet adhesion evaluation, we utilized per- centage area of platelet coverage, which is a well-accepted approach in literature. [10–15] Studies that have reported the number of platelets [16,17] (to evaluate platelet adhesion) have primarily used platelet-poor plasma or diluted plasma solu- tion because it allows one to count individual platelets. How- ever, when undiluted, platelet rich plasma solution is used (such as in our study), counting the precise number of in- dividual platelets is virtually impossible because of cluster- ing of platelets. In such studies, reporting percentage area of platelet coverage (f adh in our paper) is a more appropri- ate method and has been used frequently in literature, [10–15] including some of the studies cited by Braune et al. [8,18] In addition, the percentage area of platelet coverage allows us to study and report a more macroscopic measure of platelet adhesion rather than a highly localized measure of platelet adhesion. [19,20] 5. Regarding the point made about why platelet adhesion meas- urements reported through fluorescence microscopy are not the same as those estimated by Braune et al. from our SEM images, it must be noted that the two are not comparable. Platelet adhesion, as reported, is a macroscopic measure S. Movafaghi, Dr. V. Leszczak, Dr. W. Wang, J. A. Sorkin, Prof. L. P. Dasi, Prof. K. C. Popat, Prof. A. K. Kota Department of Mechanical Engineering Colorado State University Fort Collins, CO 80523, USA E-mail: ketul.popat@colostate.edu; arun.kota@colostate.edu Prof. L. P. Dasi, Prof. K. C. Popat, Prof. A. K. Kota School of Biomedical Engineering Colorado State University Fort Collins, CO 80523, USA Prof. L. P. Dasi Department of Biomedical Engineering Dorothy Davis Heart and Lung Research Institute Ohio State University Columbus, OH 43210, USA The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adhm.201700647. Hemocompatibility We are pleased that our recent publication [1] on the hemocom- patibility of superhemophobic titania surfaces is prompting discussion in the field. In what follows, we respond to the comment by Braune et al., who have requested for additional information that may help further understand and interpret our data as well as voiced the need for standardization of hemocompatibility. 1. In our experiments, whole blood from healthy individuals was drawn into standard 10 mL ethylenediaminetetraacetic acid (EDTA) coated vacuum tubes (which does not require recalcification) [2] using venipuncture by a phlebotomist. The protocol for blood isolation from healthy individuals was approved by Colorado State University Institutional Review Board. To account for the platelet plug and locally activated platelets resulting from the needle insertion, the first tube was discarded. The blood vials were centrifuged at 300 g for 15 min to separate the plasma from the erythrocytes. The plasma was then pooled into fresh tubes and allowed to sit for 15 min prior to being used. Each surface was exposed to 500 µL of pooled platelet rich plasma and the entire experi- ment was done within 2 h of blood removal. 2. As far as statistical analysis is concerned, the data corresponds to a minimum of three repetitions with blood drawn from a minimum of three different healthy individuals. In each test, at least three samples of each surface were studied and from each sample at least five images were captured (n = 15). The data that is presented (i.e., the arithmetic mean and standard deviation) is only from one donor (from a minimum of three repetitive samples of each surface). This is because there is Adv. Healthcare Mater. 2017, 1700647