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AIE-active non-conjugated poly(N-vinylcaprolactam) as a fluorescent thermometer for intracellular temperature imaging.

ABSTRACT: Since temperature is one of the most significant physiological parameters that dictate the cellular status of living organisms, accurate intracellular temperature measurement is crucial and a valuable biomarker for the diagnosis and treatment of diseases. Herein, we introduce the foremost example of a non-conjugated polymer as a next generation fluorescent thermometer which is capable of addressing the key shortcomings including toxicity and thermal-induced fluorescence quenching associated with ?-? conjugated system-based thermometers developed so far. We revealed, for the first time, the unique photophysical and aggregation-induced emission (AIE) characteristics of well-known thermoresponsive poly(N-vinylcaprolactam) (PNVCL) devoid of any classical fluorophore entity. PNVCL underwent a coil to globular conformational transition in an aqueous medium and appeared to be fluorescent above its lower critical solution temperature (LCST) near body temperature (38 °C). Eventually, this intriguing aspect enabled higher cellular uptake of PNVCL at the LCST boundary. By virtue of the AIE effect, the thermo-induced aggregation phenomenon has been ingeniously utilized to apply PNVCL as a novel fluorescent thermometer for intracellular temperature determination.

SUBMITTER: Saha B

PROVIDER: S-EPMC7012023 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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AIE-active non-conjugated poly(<i>N</i>-vinylcaprolactam) as a fluorescent thermometer for intracellular temperature imaging.

Saha Biswajit B Ruidas Bhuban B Mete Sourav S Mukhopadhyay Chitrangada Das CD Bauri Kamal K De Priyadarsi P

Chemical science 20191028 1

Since temperature is one of the most significant physiological parameters that dictate the cellular status of living organisms, accurate intracellular temperature measurement is crucial and a valuable biomarker for the diagnosis and treatment of diseases. Herein, we introduce the foremost example of a non-conjugated polymer as a next generation fluorescent thermometer which is capable of addressing the key shortcomings including toxicity and thermal-induced fluorescence quenching associated with ...[more]

PMID: 32110365

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Project description:The clinical development of the anticancer drug chlorambucil (CHL) is limited by its low solubility in water, poor bioavailability, and off-target toxicity. Besides, another constraint for monitoring intracellular drug delivery is the non-fluorescent nature of CHL. Nanocarriers based on block copolymers of poly(ethylene glycol)/poly(ethylene oxide) (PEG/PEO) and poly(ε-caprolactone) (PCL) are an elegant choice for drug delivery applications due to their high biocompatibility and inherent biodegradability properties. Here, we have designed and prepared block copolymer micelles (BCM) containing CHL (BCM-CHL) from a block copolymer having fluorescent probe rhodamine B (RhB) end-groups to achieve efficient drug delivery and intracellular imaging. For this purpose, the previously reported tetraphenylethylene (TPE)-containing poly(ethylene oxide)-b-poly(ε-caprolactone) [TPE-(PEO-b-PCL)2] triblock copolymer was conjugated with RhB by a feasible and effective post-polymerization modification method. In addition, the block copolymer was obtained by a facile and efficient synthetic strategy of one-pot block copolymerization. The amphiphilicity of the resulting block copolymer TPE-(PEO-b-PCL-RhB)2 led to the spontaneous formation of micelles (BCM) in aqueous media and successful encapsulation of the hydrophobic anticancer drug CHL (CHL-BCM). Dynamic light scattering and transmission electron microscopy analyses of BCM and CHL-BCM revealed a favorable size (10-100 nm) for passive targeting of tumor tissues via the enhanced permeability and retention effect. The fluorescence emission spectrum (λex 315 nm) of BCM demonstrated Förster resonance energy transfer between TPE aggregates (donor) and RhB (acceptor). On the other hand, CHL-BCM revealed TPE monomer emission, which may be attributed to the π-π stacking interaction between TPE and CHL molecules. The in vitro drug release profile showed that CHL-BCM exhibits drug release in a sustained manner over 48 h. A cytotoxicity study proved the biocompatibility of BCM, while CHL-BCM revealed significant toxicity to cervical (HeLa) cancer cells. The inherent fluorescence of RhB in the block copolymer offered an opportunity to directly monitor the cellular uptake of the micelles by confocal laser scanning microscopy imaging. These results demonstrate the potential of these block copolymers as drug nanocarriers and as bioimaging probes for theranostic applications.

Project description:Aggregation induced emission (AIE)-active bright two-photon fluorescent probes with second near-infrared (NIR-II) light excitability can be used for efficient brain bioimaging studies, wherein the fabrication of water-dispersible nanoparticles by encapsulating the hydrophobic probes with amphiphilic polymer holds the key to ensuring biocompatibility and in vivo adaptability. However, barely any study has evaluated the structural requirements that can substantially affect the water-dispersible nanoparticle formation ability of an organic AIE-active dye with amphiphilic polymers. The present study systematically assessed the structural dependency of a well-known acrylonitrile based AIE system/fluorogenic core upon the formation of water-dispersible nanoparticles and elucidated how the structural modifications can impact the in vivo two-photon imaging. Methods: A total of four acrylonitrile-based aggregation induced emission (AIE)-active two-photon (TP) fluorescent probes (AIETP, AIETP C1, AIETP C2 and AIETP C3) have been judiciously designed and synthesized with structural variations to realize how the structural alterations could substantially influence the water-dispersible nanoparticle formation ability (with amphiphilic polymers) and photo-stability to impact the in vivo imaging. Results: It has been found that the incorporation of the phenyl-thiazole unit in AIETP, AIETP C2 and AIETP C3 facilitated the formation of water-dispersible nanoparticles (NPs) with amphiphilic polymers (Pluronic F127) whereas the presence of only phenyl moiety instead in AIETP C1 could not meet the suitable condition to form the NPs with good aqueous dispersibility. Rationally designed AIETP NPs that exhibited higher brightness, improved photostability and good two-photon absorption cross section was successfully employed for in vivo brain vasculature imaging. Conclusions: Robust noninvasive 2D and 3D two-photon (NIR-II light, 1040 nm) brain vasculature imaging with beneficial attributes such as outstanding penetration depth (800 µm) and exceptional spatial resolution (1.92 µm), were achieved by utilizing AIETP NPs in this study.

Dataset Information

AIE-active non-conjugated poly(N-vinylcaprolactam) as a fluorescent thermometer for intracellular temperature imaging.

Publications

AIE-active non-conjugated poly(<i>N</i>-vinylcaprolactam) as a fluorescent thermometer for intracellular temperature imaging.

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