Verma et al. Nanoscale Res Lett 2011, 6:16 http://www.nanoscalereslett.com/content/6/1/16 Page 7 of 7 Figure 8 Thin section of mycelium of A. clavatus after treatment with 1 mM HAuCl4 for 72 h. The polydispersity in morphology of the gold nanoparticle was observed (a–c). However, triangular nanoparticles are dominantly observed with variation in shape and edge margins (a–b) (Scale bar 200 nm for a, and 50 nm for b, c). Conclusions In summary, we have demonstrated the shape controlled biosynthesis of gold nanotriangles using endophytic fungi Aspergillus clavatus, isolated from surface sterilized stem tissues of Azadirachta indica A. Juss. Results showed that triangular gold nanoparticles are formed along with some spherical as well as hexagonal morphology. It was also observed that the synthesis of gold nanotriangles are extracellular and showing a high aspect ratio. The study reported herein serve as a unique single-step green pro- tocol for the generation and stabilization of nontoxic gold nanotriangles (GNT), exploitable in a myriad of diagnostic and therapeutic applications. A. clavatus induced synthesis of GNT will provide unprecedented opportunities towards the design and development of engineered ‘green’ gold nanotriangles that can be widely utilized in biomedical applications. Acknowledgements This work is a part of the PhD thesis of VCV, and was financially supported from Council of Scientific and Industrial Research (CSIR-09/013(205)/2008/ EMR-I, dt.28-09-2008), New Delhi India. Authors are thankful to the Professor- in-charge, Centre of Experimental Medicine and Surgery (CEMS). Authors also extend their thanks to Dr. R. N. Kharwar, Mycopathology and Microbial Technology Laboratory, CAS in Botany, Banaras Hindu University India for his support and help to conduct some part of this work in his laboratory. 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