Controlled micellar disassembly of photo- and pH-cleavable linear-dendritic block copolymers

Abstract

A linear-dendritic block copolymer with both photo-and pH-cleavable linkages at the junction between the hydrophobic dendron and hydrophilic linear polymer was synthesised. The photocleavable o-nitrobenzyl group attached to alkyne was introduced at the focal point of polyester dendron and acid-degradable acetal linkage with terminal azide was introduced at one end of linear polyethylene glycol. The two segments were connected using click chemistry. The copolymer was found to self-assemble into micelle-like aggregates in dilute aqueous solution. Stimuli-responsive disassembly of the aggregates was studied by monitoring fluorescence emission of the encapsulated hydrophobic dye and dynamic light scattering (DLS). Products of acetal cleavage at acidic pH were analyzed by gel permeation chromatography and NMR spectroscopy. The photo and pH stimuli were applied separately as well as simultaneously to study the rate of dye release.Synergistic effect of the two stimuli on dye release was demonstrated and non-cytotoxic nature of the polymer was shown using MTT assay. Cell uptake of DOX-loaded micelles and photo-induced release of the drug resulting in significantly higher cytotoxicity than by free DOX was demonstrated using MDA-MB-231 cells.6 was replaced by fresh growth media and the cells were allowed to grow for further 24h under the same culture condition. Cellular uptake and intra-cellular DOX release studied by epifluorescence microscopyMDA-MB-231 cells were seeded in 24 well plate at a density of 50,000 cells/well in DMEM containing 10% FBS. The plate was incubated at 37 °C with 5% CO 2 for 24h. After incubation the media was replaced with DOX-loaded micelles, incubated for 2 h and irradiated under UV light (365nm) for 30 minutes. At the end, cells were washed 3 times with PBS and fixed with 4% paraformaldehyde. Nucleus was stained with DAPI. Images were acquired using epifluorescence microscope by Carl Zeiss (Model: Axio Observer.Z1, Oil emersion objective, 63X). (Filters set 49 DAPI shift free EX G 365, BS FT 395, EM BP 445/50, Filter set 20 Rhodamin shift freeEX BP 54.6112, BS FT 560, EM BP 575-640). Results and discussionSynthesis. Bis-MPA-based polyester dendron and polyethylene glycol (PEG) were selected as hydrophobic and hydrophilic components of the block copolymer, respectively. The o-nitrobenzyl (ONB) group is known to cleave under UV irradiation as well as by two photon absorption in the near infrared (NIR) region 34,43 while acetal linkage is known to cleave under mild acidic conditions. 28,44 Moreover, there is large difference in their rates of cleavage so that drug release can be fine tuned by controlling the time of exposure.

An l-proline based thermoresponsive and pH-switchable nanogel as a drug delivery vehicle

“…The stimuli-responsive drug release of nanogel N30D was probed by monitoring the fluorescence emission of NBA upon release, 58 benefiting from the unique emission of this species at 665 nm (λ ex 634 nm). The release of NBA was measured at different time intervals (4 h, 10 h and 24 h), at three different pHs (7.4, 6.5 and 5.2) and at two temperatures (23°C and 43°C, the VPTT of N30D).…”

Synthesis and tunable thermoresponsive solution morphologies of 2,2‐bis‐methylolpropionic acid dendron–azobenzene–poly(N‐isopropyl acrylamide) copolymers

“…Acetonide‐protected bis‐MPA‐G2‐alkyne. This dendron was synthesized by following a reported procedure …”

“…This dendron was synthesized by following a reported procedure. 45 Compound 1. This compound was synthesized by reacting 4-aminobenzyl alcohol (5 g, 0.04 mmol) in NaNO 2 /HCl solution with phenol (4.58 g, 0.048 mmol) and KOH (4.47 g, 0.07 mmol) following a reported procedure.…”

Light‐Triggered Cancer Cell Specific Targeting and Liposomal Drug Delivery in a Zebrafish Xenograft Model

“…Two photon excitation sources, for example, can be used to focus light within femtoliter (fL) volumes at tissue depths of up to 1 cm,17,18 while deeper tissues/pathologies can be accessed using fiber optic LEDs or injectable microLEDs 19–21. Although the use of light to dePEGylate nanomedicines has mainly been used to trigger extracellular drug release from a nanocarrier,22–27 enhanced tumor targeting and active cellular uptake of dual responsive polymersomes following light activation has recently been reported 28. In this case, near‐infrared (NIR) light was used in combination with upconverting nanoparticles (UCNPs) to achieve efficient nanoparticle dePEGylation deep within a murine xenograft tumor.…”

“…[1,2] All function through passive targeting of solid tumors via the enhanced permeability and retention (EPR) effect-a phenomenon characterized by the ill-defined ("leaky") vasculature and poor lymphatic drainage of select solid tumors. [3,4] To maximize passive targeting to solid tumors, PEGylation of nanoparticle surfaces is a long-standing strategy to reduce serum protein absorption, limit nanoparticle recognition and clearance by the reticulo-endothelial system (RES) in nanomedicines has mainly been used to trigger extracellular drug release from a nanocarrier, [22][23][24][25][26][27] enhanced tumor targeting and active cellular uptake of dual responsive polymersomes following light activation has recently been reported. [28] In this case, near-infrared (NIR) light was used in combination with upconverting nanoparticles (UCNPs) to achieve efficient nanoparticle dePEGylation deep within a murine xenograft tumor.…”