Facile Dye-Initiated Polymerization of Lactide–Glycolide Generates Highly Fluorescent Poly(lactic-co-glycolic Acid) for Enhanced Characterization of Cellular Delivery

Abstract

Poly­(lactic-co-glycolic acid) (PLGA) is a versatile synthetic copolymer that is widely used in pharmaceutical applications. This is because it is well-tolerated in the body, and copolymers of varying physicochemical properties are readily available via ring-opening polymerization. However, native PLGA polymers are hard to track as drug delivery carriers when delivered to subcellular spaces, due to the absence of an easily accessible “handle” for fluorescent labeling. Here we show a one-step, scalable, solvent-free, synthetic route to fluorescent blue (2-aminoanthracene), green (5-aminofluorescein), and red (rhodamine-6G) PLGA, in which every polymer chain in the sample is fluorescently labeled. The utility of initiator-labeled PLGA was demonstrated through the preparation of nanoparticles, capable of therapeutic subcellular delivery to T-helper-precursor-1 (THP-1) macrophages, a model cell line for determining in vitro biocompatibility and particle uptake. Super resolution confocal fluorescence microscopy imaging showed that dye-initiated PLGA nanoparticles were internalized to punctate regions and retained bright fluorescence over at least 24 h. In comparison, PLGA nanoparticles with 5-aminofluorescein introduced by conventional nanoprecipitation/encapsulation showed diffuse and much lower fluorescence intensity in the same cells and over the same time periods. The utility of this approach for in vitro drug delivery experiments was demonstrated through the concurrent imaging of the fluorescent drug doxorubicin (λex = 480 nm, λem = 590 nm) with carrier 5-aminofluorescein PLGA, also in THP-1 cells, in which the intracellular locations of the drug and the polymer could be clearly visualized. Finally, the dye-labeled particles were evaluated in an in vivo model, via delivery to the nematode Caenorhabditis elegans, with bright fluorescence again apparent in the internal tract after 3 h. The results presented in this manuscript highlight the ease of synthesis of highly fluorescent PLGA, which could be used to augment tracking of future therapeutics and accelerate in vitro and in vivo characterization of delivery systems prior to clinical translation.

2‐Methyltetrahydrofuran (2‐MeTHF) as a versatile green solvent for the synthesis of amphiphilic copolymers via ROP, FRP, and RAFT tandem polymerizations

“…However, discrepancies in terms of molecular weight values ( 1 HNMR calculated versus measured via GPC, Table 2) were observed, likely due to the significant chemical differences between our amphiphilic materials and the PMMA standards. This observation is known from literature [ 25 ] and might be due to the presence of various polymer‐column interactions and different solvated volumes. Differences between molecular weight calculated by 1 HNMR and GPC were noticed consistently throughout the series of amphiphilic and hybrid polymers generated in this paper.…”

“…These hybrid materials have the potential to show altered degradation profile and reduced toxicity compared to polymers synthesized simply by radical polymerizations. [29] Full conversion of macromonomers (PEGMA-LA 25 and HEMA-LA 25 ) into grafted-polymer was observed for the FRP reactions, while a conversion of around 70% was calculated for the two polymers polymerized by RAFT (when DP 15 was targeted) after the same reaction timeframe of 18 hr (Figure 3), therefore the theoretical M n was calculated to be 39 kDa for HEMA-LA 25 and 41 kDa for PEGMA-LA 25 . GPC analysis detected a single (although slightly asymmetric, possibly indicative of minimal amount of side reactions) polymeric species only for the RAFT synthesized polymers (Figure 3c, top), indicating that the macromonomers were compatible to the tandem ROP controlled radical reaction cycle, while broad bimodal peaks were detected in both the FRP prepared polymers (Figure 3c, bottom).…”

Loading of Coal Tar in Polymeric Nanoparticles as a Potential Therapeutic Modality for Psoriasis

“…The concentration of the NP suspension was determined by freeze-drying 1 mL of the suspended NPs and weighing the resulting mass. 49 The NP formulations were kept at 4 °C until further characterization. No surfactants were added at any step of NP preparation.…”

Recent Advances in Luminescence Imaging of Biological Systems Using Lanthanide(III) Luminescent Complexes

“…Using this strategy, La0.9Tb0.1F3 NPs decorated with 3,3′-((butane-1,4diylbis(azanediyl))bis(carbonyl))bis(2-hydroxybenzoic acid) -LNP -were used in luminescence imaging of HeLa cells (Figure 10) [100]. Polymeric systems have high absorption cross-section, high photostability, and, similar to NPs, offers the possibility of multi functionalities through the attachment of different compounds throughout the polymeric chain [101][102][103][104][105]. The broad emission bands and the low emission lifetimes are disadvantages of polymeric systems for use in luminescence imaging.…”