A simple method for preparation of molecularly imprinted nanoﬁber materials with signal transduction abilityw Keiichi Yoshimatsu, a Lei Ye,* a Patrik Stenlund b and Ioannis S. Chronakis* b Received (in Cambridge, UK) 20th December 2007, Accepted 31st January 2008 First published as an Advance Article on the web 20th February 2008 DOI: 10.1039/b719586a A simple electrospinning method is developed to introduce signal transduction ability into molecularly imprinted nanoﬁbers. Molecularly imprinted polymers (MIPs) are synthetic polymer materials having tailor-made molecular recognition abilities. 1 Compared to biological receptors (e.g. antibodies, enzymes, etc.) that are commonly used in bioanalysis, MIPs have far higher chemical and physical stabilities 2 and can be easily synthesized on a large scale. Due to these desirable properties, MIPs are attracting increasing attention to be used as recogni- tion elements for development of new analytical assays and chemical sensors, 3 and also new logic gates selective for predetermined chemical inputs. 4 In addition to improving binding aﬃnity and speciﬁcity of MIPs, an important research topic is to introduce signal transduction ability into MIPs. 5,6 Direct read-out of a binding event without a separation step enables to construct rapid and automated high through-put assays, which is a powerful tool not only for clinical/environ- mental analysis but also for modern drug discovery. 7 One strategy to introduce signal transduction ability into MIPs is the use of specially designed ﬂuorescent reporter monomers, which change ﬂuorescence emission upon interacting with target molecules. 6 The drawback of this approach is that for each new target molecule, a time-consuming process is often needed to develop a suitable ﬂuorescent monomer. Rather than relying on complicated design and synthesis of diﬀerent functional monomers, we have previously reported a strategy based on the principle of scintillation proximity assay, 5 where a general-purpose scintillator monomer was incorporated into MIP microspheres. Although the scintillator monomers can be used in diﬀerent imprinting systems, they require additional aromatic monomers to convert radioisotope decay into short- wavelength emission, which can excite the adjacent scintillator to emit ﬂuorescence. In some cases, co-polymerization of aromatic monomer may not be favorable or even incompatible with obtaining an optimal imprinting eﬀect. Thus, more generally applicable method to introduce signaling ability into MIPs is highly desirable. In this communication, we report a new method for preparation of MIP-based sensing nanoﬁber materials having signal transduction ability using a simple electrospinning technique. 8 The MIP nanoﬁbers obtained can be readily applied in non-separation assays for detection of a hypertension drug, (S)-propranolol. With this new method, propranolol-imprinted MIP nano- particles 9 were encapsulated into reporter-doped electrospun polystyrene (PS) nanoﬁbers. The reporter was chosen to oﬀer maximal energy transfer eﬃciency and not prone to leak from the PS nanoﬁbers. In this way we can easily introduce signal transduction ability into virtually all types of small MIP materials. It allows to synthesize MIPs always under an optimal condition to achieve the best binding sites, and thus makes the method generally applicable to a broad range of target molecules. For comparison, non-imprinted control nanoparticles were also encapsulated into reporter-doped nanoﬁbers and tested. The principle of proximity scintillation is based on the fact that b-particles emitted from a radioisotope can only travel a short distance in aqueous solution (about 1 mm in the case of 3 H). 10 It is only when 3 H-labeled analytes are located in proximity of aromatic compounds and scintillator, that the following steps of energy conversion can take place: (1) excitation of aromatic compounds by b-particles, (2) energy transfer from aromatic compounds to the scintillator, and (3) emission of a long-wavelength photon from the scintillator. A schematic illustration of signal transduction in the present proximity scintillation material is shown in Scheme 1. Polystyrene (PS) was chosen as a supporting polymer matrix since it can provide the function of the aromatic compounds. Using electrospinning, PS nanoﬁbers containing an organic scintillator, 9,10-diphenylanthracene (DPA) were easily ob- tained. The nanoﬁbers are uniform and randomly oriented, with an average diameter of about 350 nm (see ESIw). Furthermore, DPA-doped nanoﬁbers containing proprano- lol-MIP nanoparticles (Fig. 1(a)–(c)) and ﬁbers containing control nanoparticles (Fig. 1(d)–(f)) were also prepared using electrospinning. The nanoﬁbers containing nanoparticles have a diameter in the range of 250–500 nm with satisfactorily uniform morphology. The diameter of these nanoﬁbers is slightly increased due to the encapsulation of the nanoparti- cles, which is in agreement with our previous results when MIP nanoparticles were encapsulated in poly(ethylene terephtha- late) ﬁbers. 11 In this work, DPA was incorporated into PS nanoﬁbers without chemical bonding, since its hydrophobic character suggested low possibility of leakage when used in polar or aqueous solvent. Indeed, less than 3% of DPA could a Pure and Applied Biochemistry, Chemical Center, Lund University, Lund, Sweden. E-mail: Lei.Ye@tbiokem.lth.se; Fax: 46 46 2229560; Tel: 46 46 2224611 b Swerea IVF, Swedish Institute for Industrial Research and Development, Mo ¨lndal, Sweden. E-mail: Ioannis.Chronakis@swerea.se; Fax: 46 31 7066363; Tel: 46 31 7066300 w Electronic supplementary information (ESI) available: Details of nanoparticle synthesis, electrospinning and scintillation measurement. See DOI: 10.1039/b719586a 2022 | Chem. Commun., 2008, 2022–2024 This journal is  c The Royal Society of Chemistry 2008 COMMUNICATION www.rsc.org/chemcomm | ChemComm Published on 20 February 2008. Downloaded by Kyungpook National University on 08/06/2017 08:35:17. View Article Online / Journal Homepage / Table of Contents for this issue