ORIGINAL RESEARCH Chitosan biopolymer functionalized gold nanoparticles with controlled cytotoxicity and improved antifilarial efficacy Pranesh Chowdhury 1 & Bishnupada Roy 1 & Niladri Mukherjee 2 & Suprabhat Mukherjee 2 & Nikhilesh Joardar 2 & Maloy Kr. Mondal 1 & Debiprasad Roy 1 & Santi P. Sinha Babu 2 Received: 20 January 2018 /Accepted: 4 May 2018 /Published online: 31 May 2018 # Springer International Publishing AG, part of Springer Nature 2018 Abstract Ultra-high stable chitosan functionalized gold nanoparticles (GNPs) of desired biopolymeric corona are synthesized without adding conventional hazardous reducing agents. The inherent unique set of properties like reducing ability, stabilizing effect, and mucoadhesiveness of chitosan is exhibited in the present work. Morphologies and ultra-stability of the synthesized materials are characterized by standard techniques. The mucoadhesiveness of the synthesized materials are well documented through the biological potency of the synthesized GNPs. The prominent bioactivity is evident from the antifilarial activity. The cellular and molecular level studies on the induction of oxidative stress, DNA damage, and undesirable protein expression clearly explain the antifilarial activities. Interestingly, the developed nanoparticle shows no detectable sign of toxicity when evaluated in vitro (rat peritoneal MФ) or in vivo (Wistar rat). Therefore, the synthesized green GNPs appear to be a substantial promise as an efficacious broad-spectrum nanotherapeutic agent with safe outcome for clinical attempt. Keywords Antifilarial activities . Biopolymer . Chitosan . Cytotoxicity . Gold nanoparticles . Mucoadhesiveness 1 Introduction Chitosan is one of the most abundant natural biopolymers, obtained from chitin. Chemically, it is a random co-polymer of β-(1-4)-linked D-glucosamine and N-acetyl-D-glucos- amine. The presence of hydrophilic hydroxyl groups makes the co-polymer suitable for super absorption of water [1]. The majorities of polysaccharides are normally neutral or nega- tively charged in an acidic environment. However, chitosan is positively charged in the same environment due to its amino groups. This distinct characteristic induces bioactivity of the chitosan. The other interesting features of chitosan are suscep- tibility to chemical modifications, biocompatibility, non-tox- icity, low allergenicity, and biodegradability [2]. Many recent reviews [3, 4] focus on clinical use of chitosan-based compos- ite (with quantum dots, nanoparticles, and carbon dots) and chitosan-mediated fabrication of metal nanocomposites for biomedical applications. Lymphatic filariasis (LF), a vector-borne disease, is caused by filarial parasites Wuchereria bancrofti, Brugia malayi, and Brugia timori. As per report of WHO, it causes havoc mainly in tropical and subtropical countries due to favorable atmosphere for the growth of filarial parasites. The WHO initiated a drive to eliminate the filarial disease by 2020 [5]. Thus, the search for a new therapeutic solu- tion against human lymphatic filariasis has emerged as a thrust-driven area of research. Systemic chemotherapeutic targeting of filarial parasites is unfocused due to their deep-seated location in lymphatic vessels. Chourasia et al. [6] reported that the peculiarity of lymphatic vasculature underneath the subcutaneous layer of skin preferentially allows entry of only 10–100 nm- sized particles. Hence, out of several promising therapeutic modalities, exploiting metal nanoparticles for targeted ap- optosis is considered as the effective means for treating the Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42114-018-0040-7) contains supplementary material, which is available to authorized users. * Pranesh Chowdhury pranesh_02@yahoo.co.in 1 Polymer & Nano Research Laboratory, Department of Chemistry, Visva-Bharati University, Santiniketan, India 2 Parasitology Laboratory, Department of Zoology (Centre for Advanced Studies), Visva-Bharati University, Santiniketan 731235, India Advanced Composites and Hybrid Materials (2018) 1:577–590 https://doi.org/10.1007/s42114-018-0040-7