IR780-polymer conjugates for stable near-infrared labeling of biodegradable polyester-based nanocarriers

PEGylated and functionalized polylactide-based nanocapsules: An overview

Polymeric nanocapsules (NC) are versatile mixed vesicular nanocarriers, generally containing a lipid core with a polymeric wall. They have been first developed over four decades ago with outstanding applicability in the cosmetic and pharmaceutical fields. Biodegradable polyesters are frequently used in nanocapsule preparation and among them, polylactic acid (PLA) derivatives and copolymers, such as PLGA and amphiphilic block copolymers, are widely used and considered safe for different administration routes. PLA functionalization strategies have been developed to obtain more versatile polymers and to allow the conjugation with bioactive ligands for cell-targeted NC. This review intends to provide steps in the evolution of NC since its first report and the recent literature on PLA-based NC applications. PLA-based polymer synthesis and surface modifications are included, as well as the use of NC as a novel tool for combined treatment, diagnostics, and imaging in one delivery system. Furthermore, the use of NC to carry therapeutic and/or imaging agents for different diseases, mainly cancer, inflammation, and infections is presented and reviewed. Constraints that impair translation to the clinic are discussed to provide safe and reproducible PLA-based nanocapsules on the market. We reviewed the entire period in the literature where the term "nanocapsules" appears for the first time until the present day, selecting original scientific publications and the most relevant patent literature related to PLA-based NC. We presented to readers a historical overview of these Sui generis nanostructures.

Review of quantitative and qualitative methods for monitoring photopolymerization reactions

Authomatic in-situ monitoring and characterization of photopolymerization.

Poly(2-ethyl-2-oxazoline)-IR780 conjugate nanoparticles for breast cancer phototherapy

Aims: To address the limitations of IR780 by preparing hydrophilic polymer-IR780 conjugates and to employ these conjugates in the assembly of nanoparticles (NPs) intended for cancer photothermal therapy. Materials & methods: The cyclohexenyl ring of IR780 was conjugated for the first time with thiol-terminated poly(2-ethyl-2-oxazoline) (PEtOx). This novel poly(2-ethyl-2-oxazoline)-IR780 (PEtOx-IR) conjugate was combined with D-α-tocopheryl succinate (TOS), leading to the assembly of mixed NPs (PEtOx-IR/TOS NPs). Results: PEtOx-IR/TOS NPs displayed optimal colloidal stability as well as cytocompatibility in healthy cells at doses within the therapeutic range. In turn, the combination of PEtOx-IR/TOS NPs and near-infrared light reduced heterotypic breast cancer spheroid viability to just 15%. Conclusion: PEtOx-IR/TOS NPs are promising agents for breast cancer photothermal therapy.

Photodynamic therapy with the dual-mode association of IR780 to PEG-PLA nanocapsules and the effects on human breast cancer cells

IR780 is a near-infrared fluorescent dye, which can be applied as a photosensitizer in photodynamic (PDT) and photothermal (PTT) therapies and as a biodistribution tracer in imaging techniques. We investigated the growth and migration inhibition and mechanism of death of breast tumor cells, MCF-7 and MDA-MB-231, exposed to polymeric nanocapsules (NC) comprising IR780 covalently linked to the biodegradable polymer PLA (IR-PLA) and IR780 physically encapsulated (IR780-NC) in vitro. Both types of NC had mean diameters around 120 nm and zeta potentials around -40 mV. IR-PLA-NC was less cytotoxic than IR780 NC to a non-tumorigenic mammary epithelial cell line, MCF-10A, which is an important aspect of selectivity. Free-IR780 was more cytotoxic than IR-PLA-NC for MCF-7 and MDA-MB-231 cells after illumination with a 808 nm laser. IR-PLA NC was effective to inhibit colony formation (50%) and migration (30-40%) for both cancer cell lines. MDA-MB-231 cells were less sensitive to all IR780 formulations compared to MCF-7 cells. Cell uptake was higher with IR-PLA-NC than with IR780-NC and free-IR780 in both cancer cell lines (p < 0.05). NC uptake was higher in MCF-7 than in MDA-MB-231 cells. IR-PLA-NC induced a higher percentage of apoptosis upon illumination in MDA-MB-231 than in MCF-7 cells. The necrosis mechanism of death predominated in treatments with free-IR780 and with encapsulated IR780 NC, suggestive of damages at the plasma membrane. IR780 conjugated with PLA increased the apoptotic pathway and demonstrated potential as a multifunctional theranostic agent for breast cancer treatment with increased cellular uptake, photodynamic activity and more reliable tracking in cell-image studies.

Asymmetric flow field-flow fractionation (AF4) with fluorescence and multi-detector analysis for direct, real-time, size-resolved measurements of drug release from polymeric nanoparticles

Polymeric nanoparticles (NPs) are typically designed to enhance the efficiency of drug delivery by controlling the drug release rate. Hence, it is critical to obtain an accurate drug release profile. This study presents the first application of asymmetric flow field-flow fractionation (AF4) with fluorescence detection (FLD) to quantify release profiles of fluorescent drugs from polymeric NPs, specifically poly(lactic-co-glycolic acid) NPs loaded with enrofloxacin (PLGA-Enro NPs). In contrast to conventional measurements requiring separation of the NPs and dissolved drugs (typically by dialysis) prior to quantification, AF4 provides in situ removal of unincorporated drugs, while the judicious combination of online FLD and UV detection selectively provides the entrapped drug and PLGA NP concentrations, respectively, and hence the drug loading. NP size and shape factors are simultaneously obtained by online dynamic and multi-angle light scattering (DLS, MALS) detectors. The AF4 and dialysis approaches were compared to evaluate drug release from PLGA-Enro NPs containing a high proportion (≈ 94%) of unincorporated (burst release) drug at three temperatures spanning the glass transition temperature (T_g ≈ 33 °C) of the NPs. The AF4 method clearly captured the temperature dependence of the drug release relative to T_g (from no release at 20 °C to rapid release at 37 °C). In contrast, dialysis was not able to distinguish differences in the extent or rate of release of the entrapped drug because of interferences from the burst release, as well as the dialysis lag time, as supported through a diffusion model and validation experiments on purified NPs with low burst release. Finally, the multi-detector AF4 analysis yielded unique size-dependent release profiles across the entire NP size distribution, with smaller NPs showing faster release consistent with radial diffusion from the NPs. Overall, this study demonstrates the novel application and advantages of multi-detector AF4 methods, particularly AF4-FLD, to obtain direct, size-resolved release profiles of fluorescent drugs from polymeric NPs.

Asymmetric flow field-flow fractionation as a multifunctional technique for the characterization of polymeric nanocarriers

The importance of polymeric nanocarriers in the field of drug delivery is ever-increasing, and the accurate characterization of their properties is paramount to understand and predict their behavior. Asymmetric flow field-flow fractionation (AF4) is a fractionation technique that has gained considerable attention for its gentle separation conditions, broad working range, and versatility. AF4 can be hyphenated to a plurality of concentration and size detectors, thus permitting the analysis of the multifunctionality of nanomaterials. Despite this potential, the practical information that can be retrieved by AF4 and its possible applications are still rather unfamiliar to the pharmaceutical scientist. This review was conceived as a primer that clearly states the "do's and don'ts" about AF4 applied to the characterization of polymeric nanocarriers. Aside from size characterization, AF4 can be beneficial during formulation optimization, for drug loading and drug release determination and for the study of interactions among biomaterials. It will focus mainly on the advances made in the last 5 years, as well as indicating the problematics on the consensus, which have not been reached yet. Methodological recommendations for several case studies will be also included.

Release, transfer and partition of fluorescent dyes from polymeric nanocarriers to serum proteins monitored by asymmetric flow field-flow fractionation

Fluorescent probes are used in drug nanocarrier pre-clinical studies or as active compounds in theranostics and photodynamic therapy. In the biological medium, nanoparticles interact with proteins, which can result in the off-target release of their cargo. The present study used asymmetric flow field-flow fractionation with online multi-angle laser light scattering and fluorescence detection (AF4-MALLS-FLD) to study the release, transfer, and partition of fluorescent dyes from polymeric nanoparticles (NP). NP formulations containing the dyes Rose Bengal, Rhodamine B, DiI, 3-(α-azidoacetyl)coumarin and its polymer conjugate, Nile Red, and IR780 and its polymer conjugate were prepared. NP suspensions were incubated in a medium with serum proteins and then analyzed by AF4. AF4 allowed efficient separation of proteins (< 10 nm) from fluorescently labeled NP (range of 54 - 180 nm in diameters). The AF4 analyses showed that some dyes, such as Rose Bengal, IR780, and Coumarin were transferred to a high extent (68-77%) from NP to proteins. By contrast, for DiI and dye-polymer conjugates, transfer occured to a lower extent. The studies of dye release kinetics showed that the transfer of IR780 from NP to proteins occurs at a high extent (~50%) and rate, while Nile Red was slowly released from the NP over time with reduced association with proteins (~20%). This experiment assesses the stability of fluorescence labeling of nanocarriers and probes the transfer of fluorescent dyes from NP to proteins, which is otherwise not accessible with commonly used techniques of separation, such as dialysis and ultrafiltration/centrifugation employed in drug encapsulation and release studies of nanocarriers. Determining the interaction and transfer of dyes to proteins is of utmost importance in the pre-clinical evaluation of drug nanocarriers for improved correlation between in vitro and in vivo studies.

A Survey of Strain-Promoted Azide-Alkyne Cycloaddition in Polymer Chemistry

Highly efficient reactions that enable the assembly of molecules into complex structures have driven extensive progress in synthetic chemistry. In particular, reactions that occur under mild conditions and in benign solvents, while producing no by-products and rapidly reach completion are attracting significant attention. Amongst these, the strain-promoted azide-alkyne cycloaddition, involving various cyclooctyne derivatives reacting with azide-bearing molecules, has gained extensive popularity in organic synthesis and bioorthogonal chemistry. This reaction has also recently gained momentum in polymer chemistry, where it has been used to decorate, link, crosslink, and even prepare polymer chains. This survey highlights key achievements in the use of this reaction to produce a variety of polymeric constructs for disparate applications.

NIR Scaffold Bearing Three Handles for Biocompatible Sequential Click Installation of Multiple Functional Arms

Near-infrared (NIR) probes are ideal for fluorescence labeling and imaging of biological targets in living animals. However, the instability of common NIR dyes hampers the construction of NIR probes bearing multiple functional components such as biomolecules for specific targeting and imaging reagents for multimodality imaging. To overcome these limitations, we designed a novel NIR scaffold bearing two terminal alkynes as clickable handles and a chloride on the heptamethine backbone that allows nucleophilic substitution with an azide to generate the third clickable handle. This unique scaffold allows for facile installation of multiple functional arms for the construction of multifunctional NIR probes. Various biomacromolecules or imaging reagents can be introduced to the NIR scaffold by sequential one-pot click reactions under biocompatible conditions. The preclickable handle chloride on the NIR backbone does not interfere with the initial click reactions, and it can be easily transformed into an azide for a following click reaction. On the basis of this unique NIR scaffold, we developed a highly efficient method to construct diverse NIR probes containing multiple functional biomolecules including peptides, antibodies, nucleic acids, and NIR/PET (positron emission tomography) dual-modality imaging probes bearing tumor-targeting groups. NIR imaging or multimodality imaging using these probes was performed on live cells or tumor models on living mice.