Fluorescent-Tagged Biodegradable Polycaprolactone Block Copolymer FRET Probe for Intracellular Bioimaging in Cancer Cells

Abstract

The present investigation reports a new fluorophore-tagged biodegradable polycaprolactone (PCL) block copolymer FRET-probe for intracellular imaging in cancer therapy. A hydroxyl functionalized π-conjugated oligo-phenylenevinylene (OPV) chromophore was tailor-made, and it was incorporated in a t-butyl ester substituted polycaprolactone block copolymer via ring opening polymerization. This blue-luminescent OPV-PCL triblock self-assembled as <200 nm spherical nanoparticles (FRET donor), and it encapsulated water insoluble Nile red (NR, FRET acceptor) to yield an OPV-NR FRET probe. Selective photo excitation of the OPV chromophore in block nanoassemblies enabled the excitation energy transfer from the OPV to NR and facilitated the efficient FRET process in aqueous medium. Time-correlated fluorescent decay dynamics and detailed photophysical studies were carried out to estimate the Förster distance, donor–acceptor distance, and the excitation energy transfer efficiency. These parameters confirmed the occurrence of the FRET process within the confined nanoparticle environment. The PCL chains in the FRET probe were susceptible to enzymatic biodegradation in intracellular environments, and the degradation process controlled the FRET on/off mechanism. Cytotoxicity studies revealed that the FRET probe was biocompatible and nontoxic to cells, and the FRET-probe was found to be readily taken up by the cancer cells, and it was internalized in the cytoplasm and peri-nuclear environment. Selective photoexcitation of the OPV chromophore in a confocal microscope exhibited dual emission from the FRET probe. The cancer cells exhibited blue luminescence (self-emission) with respect to the OPV chromophore (in the blue channel) and bright red-luminescence from the NR dye followed by the FRET process at the cellular level (in the red channel). The dual luminescence characteristics, biodegradation and biocompatibility, make the newly designed PCL-OPV-NR FRET probe an excellent biomedical nanodevice for bioimaging applications, and the proof-of-concept was established in cervical (HeLa) and breast cancer (MCF 7) cell lines.

Nanocontainers for Analytical Applications

“…If amphiphilic, nonbranched, synthetic block copolymers are applied for the formation, the nanocontainers are called polymersomes . They have a broad size range of 30 to 500 nm, but for analytical applications they are usually below 400 nm . There are several ways to synthesize polymersomes and polymeric capsules .…”

Nanocontainer in der Analytik

“…[15] Sie existieren in einem weiten Grçßenbereich von 30-500 nm, [12] füra nalytische Anwendungen sind sie aber normalerweise kleiner als 400 nm. [44][45][46][47] Es gibt verschiedene Wege,P olymersomen und polymere Kapseln herzustellen. [15] Bei [20,49] wobei das Letztgenannte in der Analytik am häufigsten zum Einsatz kommt.…”

“…Wenn amphiphile, nicht‐verzweigte, synthetische Blockcopolymere für die Bildung der Nanocontainer verwendet werden, spricht man von Polymersomen . Sie existieren in einem weiten Größenbereich von 30–500 nm, für analytische Anwendungen sind sie aber normalerweise kleiner als 400 nm . Es gibt verschiedene Wege, Polymersomen und polymere Kapseln herzustellen .…”

Effective Regulation of Polycaprolactone Molecular Weight and Oligomers Content Using Tetraphenyltin Catalyst

“…The main paragraph text follows directly on here. Polycaprolactone (PCL) has various biological applications, such as being a controlled drug release carrier, [1][2][3][4] fluorescent probe, [5] cell-encapsulation device, [6] tissue culture bed frame, [7][8][9][10][11] biological dye, [12] and medical modeling material. [8,[13][14][15][16] This is because of its excellent biodegradation [17][18][19] and biocompatibility.…”