RESEARCH ARTICLE Biocompatible fluorescent polyamine‐based cyclophosphazene hybrid nanospheres for targeted cell imaging Raheel Akram 1 | Anila Arshad 2 | Sami Ullah Dar 1 | Majid Basharat 1 | Wei Liu 1 | Shuangkun Zhang 1 | Zhanpeng Wu 1 | Dezhen Wu 3 1 Key Laboratory of Carbon Fiber and Functional Polymers, Beijing University of Chemical Technology, Ministry of Education, Beijing, China 2 State Key Laboratory of Chemical Resource Engineering, Beijing Key Laboratory of Environmentally Harmful Chemical Analysis, Beijing University of Chemical Technology, Beijing, China 3 State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China Correspondence Zhanpeng Wu, Key Laboratory of Carbon Fiber and Functional Polymers, Beijing University of Chemical Technology, Ministry of Education, Beijing 100029, China. Email: wuzp@mail.buct.edu.cn Funding information National Natural Science Foundation of China, Grant/Award Number: Project No. 51773010 51773010 Fluorescent nanoprobes are highly desirable toolkit for bioimaging applications. This study reports the first example for the synthesis of a nontoxic prototypical fluo- rescent organic compound 2‐benzo[d]thiazol‐2‐yl)‐3‐(2‐chloro‐4‐(dimethylamino) phenyl)acrylonitrile (BCA) and its entrapment into the poly[cyclotriphosphazene‐co‐ polyethyleneimine] cross‐linked (PCPEI) nanospheres named as BCA@PCPEI for targeted cell imaging application. The as‐prepared BCA@PCPEI nanospheres were thoroughly characterized by scanning electron microscopy (SEM), transmission elec- tron microscopy (TEM), fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and phosphorus‐31 nuclear magnetic resonance ( 31 P‐NMR) analyses. The sur- face functional analysis of the nanospheres was performed by X‐ray photoelectron spectroscopy (XPS), which proves that the content ratios of elements belong to the precursors concentrations. The as‐prepared nanospheres displayed emission at 606 nm with bright orange fluorescence at any concentration. Moreover, the nanospheres were also less cytotoxic and maintained remarkable cell viability up to 100 μg/mL. Owing to the fluorescence with higher emission, this material has shown excellent cell imaging performance with better targeting ability to HeLa cells. KEYWORDS BCA@PCPEI, fluorescent material, nanospheres, targeted cell imaging 1 | INTRODUCTION Fluorescence has tremendously caught the interest of researchers as a powerful tool to be widely used for bioimaging because of its high sensitivity and rich color choice. 1,2 It has been used as an influential technique for the real‐time study of the various biological units includ- ing organs, tissues, cells, and even biomolecules through various 3D models (landscape) and spatial resolutions up to nanometric scale. 3-5 Thus, it is helping to investigate the biological activities in broad range and solving the complicated structure‐activity relationship. Several aspects are necessarily required for the exogenous fluorophores to produce high‐quality bioimaging including strong brightness, suitable wavelength, high resistance to photo bleaching and protein interfer- ence, and better biocompatibility. 6 Nowadays, the analyses of cellular and superficial tissues by using fluorescent probes for biomedical imaging is highly desirable. On the basis of this, a variety of fluores- cent nanomaterials, for instance, fluorescent proteins, 7,8 semiconduc- tor quantum dots (QDs), 9-12 multifunctional nanoshells, 13 carbon dots, 14-16 rare earth–based nanoparticles (NPs), 17-20 and polyphosphazene microspheres, 21 have been utilized in optical imaging. Protein fluorophores are promising candidates in terms of biospecificity and biocompatibility, but few limitations somehow halt their widespread use including the limited selection of fluorescent proteins and less resistance to photo bleaching. 22,23 Recently, QDs and rare earth metals–based NPs are also excessively applied as bioimaging toolkit as they exhibit broad absorption band with tunable Raheel Akram and Anila Arshad contributed equally to this work. Received: 29 April 2019 Accepted: 15 September 2019 DOI: 10.1002/pat.4778 Polym Adv Technol. 2019;1–8. © 2019 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/pat 1