Controlled synthesis of camptothecin-polylactide conjugates and nanoconjugates

Magnesium-Catalyzed Dye-Embedded Polylactide Nanoparticles for the Effective Killing of Highly Metastatic B16F10 Melanoma Cells

In the current research, dye-embedded polylactic acid (PLA) conjugate materials were synthesized using one-pot ring-opening polymerization (ROP), i.e., (dtHPLA) (2-[(2,4,6-trimethylphenyl) imino]-1(2H)-acenaphthylenone-reduced-PLA) and (dmHPLA) (monoiminoacenaphtheneone-reduced-PLA), and then, nanoparticles (NPs) were engineered in the size range of 150 ± 30 nm. P(dtHPLA) NPs were employed in the treatment of melanoma, an aggressive type of skin cancer, which mandates the development of novel techniques to enhance healing outcomes and eliminate adverse effects related to existing treatments. In addition to exhibiting strong intracellular absorption in the spheroid model, the P(dtHPLA) NPs exhibited a strong cytotoxic effect on B16F10 cells, which resulted in oxidative stress from the generation of reactive oxygen species (ROS) and cell death. Additionally, a live/dead experiment using P(dtHPLA) NPs revealed a notable reduction in cell viability.

Engineering Semicarbazide-Bearing Polypeptide Conjugates for Efficient Tumor Chemotherapy and Imaging of Tumor Metastasis

Polypeptide materials offer scalability, biocompatibility, and biodegradability, rendering them an ideal platform for biomedical applications. However, the preparation of polypeptides with specific functional groups, such as semicarbazide moieties, remains challenging. This work reports, for the first time, the straightforward synthesis of well-defined methoxy-terminated poly(ethylene glycol)-b-polypeptide hybrid block copolymers (HBCPs) containing semicarbazide moieties. This synthesis involves implementing the direct polymerization of environment-stable N-phenoxycarbonyl-functionalized α-amino acid (NPCA) precursors, thereby avoiding the handling of labile N-carboxyanhydride (NCA) monomers. The resulting HBCPs containing semicarbazide moieties enable facile functionalization with aldehyde/ketone derivatives, forming pH-cleavable semicarbazone linkages for tailored drug release. Particularly, the intracellular pH-triggered hydrolysis of semicarbazone moieties restores the initial semicarbazide residues, facilitating endo-lysosomal escape and thus improving therapeutic outcomes. Furthermore, the integration of the hypoxic probe (Ir(btpna)(bpy)2 ) into the pH-responsive nanomedicines allows sequential responses to acidic and hypoxic tumor microenvironments, enabling precise detection of metastatic tumors. The innovative approach for designing bespoke functional polypeptides holds promise for advanced drug delivery and precision therapeutics.

Visible light degradable micelles for intraocular corticosteroid delivery

Visible light responsive micellar drug delivery formulations are of notable interest for the treatment of ocular diseases, as their successful development would enable controlled drug release at the back of the eye, improving efficacy and reducing side-effects when compared to existing approaches. In this work, an aliphatic polycarbonate-based visible light responsive micelle formulation based on mPEG-b-poly(5-hydroxy-trimethylene carbonate) (PHTMC) was prepared wherein the pendant hydroxyl groups of the PHTMC repeating units were protected by blue light-labile [7-(diethylamino)coumarin-4-yl]methyl (DEACM). The photo-labile DEACM provided a photo-triggered release profile, as, upon the removal of these protecting groups by photo-irradiation, the micelles underwent structural disruption, leading to the release of the payload. The removal of DEACM also deprotected the pendant hydroxyl groups of PHTMC, leading to PHTMC backbone degradation via intramolecular cyclization.

Degradation of Polymer-Drug Conjugate Nanoparticles Based on Lactic and Itaconic Acid

Tuberculosis (TB) is still a significant threat to human health. A promising solution is engineering nanoparticulate drug carriers to deliver anti-TB molecules. Itaconic acid (ITA) potentially has anti-TB activity; however, its incorporation in nanoparticles (NP) is challenging. Here we show an approach for preparing polymer-ITA conjugate NPs and a methodology for investigating the NP degradation and ITA release mechanism. The conjugate was synthesized by the two-directional growing of polylactic acid (PLA) chains, followed by capping their extremities with ITA. The poly(lactate)-itaconate PLA-ITA was then used to formulate NPs. The degradation and drug release processes of the polymer conjugate NPs were studied qualitatively and quantitatively. The molecular structures of released species were characterized by using liquid NMR spectroscopy and mass spectrometry. We discovered a complex NP hydrolysis process forming diverse oligomers, as well as monomeric lactic acid (LA) and drug ITA. The slow degradation process led to a low release of free drugs, although raising the pH from 5.3 to 7.4 induced a slight increase in the amounts of released products. TEM images showed that bulk erosion is likely to play the primary role in the degradation of PLA-ITA NPs. The overall results and methodology can be of interest for understanding the mechanisms of NP degradation and drug release of this new polymer-drug conjugate system.

Ruthenium-initiated polymerization of lactide: a route to remarkable cellular uptake for photodynamic therapy of cancer

Ruthenium complexes have attracted a lot of attention as potential photosensitizers (PSs) for photodynamic therapy (PDT). However, some of these PSs are unsuitable for PDT applications due to their low cellular uptake, which is possibly the consequence of their relatively low degree of lipophilicity, which prevents them from penetrating into tumor cells. Here, we report the simple one-pot synthesis of ruthenium-containing nanoconjugates from a non-cell-penetrating, non-phototoxic ruthenium(ii) polypyridyl complex (RuOH), by a drug-initiated ring-opening polymerization of lactide through the formation of a zinc initiator. These conjugates were then formulated into nanoparticles by nanoprecipitation and characterized by means of nuclear magnetic resonance spectroscopy (NMR), matrix-assisted laser desorption/ionization – time of flight mass spectrometry (MALDI-TOF MS) and dynamic light scattering (DLS). Finally, their photo-therapeutic activity (λ_exc = 480 nm, 3.21 J cm⁻²) in cancerous human cervical carcinoma (HeLa) and non-cancerous retinal pigment epithelium (RPE-1) cells was tested alongside that of RuOH and their cellular uptake in HeLa cells was assessed by confocal microscopy and inductively coupled plasma – mass spectrometry (ICP-MS). All nanoparticles showed improved photophysical properties including luminescence and singlet oxygen generation, enhanced cellular uptake and, capitalizing on this, an improved photo-toxicity. Overall, this study demonstrates how it is possible to transform a non-phototoxic PDT PS into an active PS using an easy, versatile polymerization technique.

This study shows the transformation of a non-phototoxic PDT photosensitizer into an active photosensitizer using an easy, versatile and generalizable one-pot ruthenium-initiated polymerization technique.

A new, simple, and efficient strategy for the preparation of active antifungal biodegradable materials via ring-opening polymerization of l-lactide with zinc aryloxides

In this work, zinc aryloxides supported by monodentate hydroxybiphenyls [ArOH: ortho-phenylphenol (o-XenOH), meta-phenylphenol (m-XenOH), or para-phenylphenol (p-XenOH] and N,N,N',N'-tetramethylethylenediamine (TMEDA) were used to develop active polymeric materials for antifungal agents for agricultural use. The direct reaction of ligand precursor ArOH with ZnEt2 (1 : 2) in a toluene/TMEDA mixture (1 : 10) afforded a series of three isostructural monomeric compounds, namely [Zn(o-XenO)2(TMEDA)] (1), [Zn(m-XenO)2(TMEDA)] (2), and [Zn(p-XenO)2(TMEDA)] (3). These were characterized by single-crystal X-ray diffraction, and spectroscopic and other analytical methods. The results show that 1-3 are effective initiators for the ring-opening polymerization (ROP) of l-lactide (l-LA) via bifunctional activation of the monomer with Lewis pairs to give polymers terminated with TMEDA and Zn(OAr)2 as the α- and ω-chain ends, respectively. Combinations of ZnEt2 with two molar equivalents of ArOH proligands were used to synthesize polylactides containing fungicide molecules covalently bonded via ester linkers. The ROP of l-LA initiated by these zinc-based systems could be used for the preparation of polyesters with promising antifungal activities.

Degradable polymer prodrugs with adjustable activity from drug-initiated radical ring-opening copolymerization

Degradable polymer prodrugs based on gemcitabine (Gem) as an anticancer drug were synthesized by 'drug-initiated' nitroxide-mediated radical ring-opening copolymerization (NMrROP) of methacrylic esters and 2-methylene-4-phenyl-1,3-dioxolane (MPDL). Different structural parameters were varied to determine the best biological performances: the nature of the monomer [i.e., oligo(ethylene glycol) methacrylate (OEGMA) or methyl methacrylate (MMA)], the nature of the Gem-polymer linker (i.e., amide or amide and diglycolate) and the MPDL content in the copolymer. Depending on the nature of the methacrylate monomer, two small libraries of water-soluble copolymer prodrugs and nanoparticles were obtained (M n ∼10 000 g mol-1, Đ = 1.1-1.5), which exhibited tunable hydrolytic degradation under accelerated conditions governed by the MPDL content. Drug-release profiles in human serum and in vitro anticancer activity on different cell lines enabled preliminary structure-activity relationships to be established. The cytotoxicity was independently governed by: (i) the MPDL content - the lower the MPDL content, the greater the cytotoxicity; (ii) the nature of the linker - the presence of a labile diglycolate linker enabled a greater Gem release compared to a simple amide bond and (iii) the hydrophilicity of the methacrylate monomer-OEGMA enabled a greater anticancer activity to be obtained compared to MMA-based polymer prodrugs. Remarkably, the optimal structural parameters enabled reaching the cytotoxic activity of the parent (free) drug.

Nanoparticles with high payloads of pipemidic acid, a poorly soluble crystalline drug: drug-initiated polymerization and self-assembly approach

Nowadays, biodegradable polymers such as poly(lactic acid) (PLA), poly(D,L-lactic-co-glycolic acid) (PLGA) and poly(ε-caprolactone) (PCL) remain the most common biomaterials to produce drug-loaded nanoparticles (NPs). Pipemidic acid (PIP) is a poorly soluble antibiotic with a strong tendency to crystallize. PIP incorporation in PLA/PLGA NPs was challenging because of PIP crystals formation and burst release. As PIP had a poor affinity for the NPs, an alternative approach to encapsulation was used, consisting in coupling PIP to PCL. Thus, a PCL-PIP conjugate was successfully synthesized by an original drug-initiated polymerization in a single step without the need of catalyst. PCL-PIP was characterized by NMR, IR, SEC and mass spectrometry. PCL-PIP was used to prepare self-assembled NPs with PIP contents as high as 27% (w/w). The NPs were characterized by microscopy, DLS, NTA and TRPS. This study paves the way towards the production of NPs with high antibiotic payloads by drug-initiated polymerization. Further studies will deal with the synthesis of novel polymer-PIP conjugates with ester bonds between the drug and PCL. PIP can be considered as a model drug and the strategy developed here could be extended to other challenging antibiotics or anticancer drugs and employed to efficiently incorporate them in NPs.

Designing Smart Polymer Conjugates for Controlled Release of Payloads

Incorporating labile bonds inside polymer backbone and side chains yields interesting polymer materials that are responsive to change of environmental stimuli. Drugs can be conjugated to various polymers through different conjugation linkages and spacers. One of the key factors influencing the release profile of conjugated drugs is the hydrolytic stability of the conjugated linkage. Generally, the hydrolysis of acid-labile linkages, including acetal, imine, hydrazone, and to some extent β-thiopropionate, are relatively fast and the conjugated drug can be completely released in the range of several hours to a few days. The cleavage of ester linkages are usually slow, which is beneficial for continuous and prolonged release. Another key structural factor is the water solubility of polymer-drug conjugates. Generally, the release rate from highly water-soluble prodrugs is fast. In prodrugs with large hydrophobic segments, the hydrophobic drugs are usually located in the hydrophobic core of micelles and nanoparticles, which limits the access to the water, hence lowering significantly the hydrolysis rate. Finally, self-immolative polymers are also an intriguing new class of materials. New synthetic pathways are needed to overcome the fact that much of the small molecules produced upon degradation are not active molecules useful for biomedical applications.

Self-stabilized, hydrophobic or PEGylated paclitaxel polymer prodrug nanoparticles for cancer therapy

Facile derivatization of paclitaxel (Ptx) and subsequent “drug-initiated” synthesis of well-defined Ptx-polymer prodrugs was performed from nitroxide-mediated polymerization or reversible addition–fragmentation chain transfer polymerization.

[Polymer nanoparticles for the delivery of anticancer drug]

Nanocarriers based on polymers are currently attracting much attention to perform efficient drug delivery, especially in cancer therapy. Over the last decades, different kinds of polymer nanoparticulate systems have been developed (e.g., simple, stealth, targeted, stimuli-responsive and prodrug) to propose novel, better and safer cancer therapies. This article will give a brief overview of the different classes of polymer nanoparticles that have been reported and discuss some key achievements deriving from their use in the field of cancer therapy.

Rapidly cell-penetrating and reductive milieu-responsive nanoaggregates assembled from an amphiphilic folate-camptothecin prodrug for enhanced drug delivery and controlled release

Self-assembled small molecular prodrug loaded with camptothecin in response to glutathione and folate receptors for combined tumour detection and treatment.

Structure–cytotoxicity relationship of drug-initiated polymer prodrug nanoparticles

Cladribine (CdA)-based polymer prodrug nanoparticles were obtained by “drug-initiated” RAFT polymerization of squalenyl methacrylate (SqMA) from two different CdA-bearing chain transfer agents (CTAs) to evaluate the influence of the nature of the linkage between CdA and the CTA, and the bulkiness of the polymer, on the drug release and the biological performance.

Dialkylgallium alkoxides – a tool for facile and stereoselective synthesis of PLA–drug conjugates

The synthesis of PLA–drug conjugates with a tunable stereostructure of the PLA fragment is demonstrated by the synthesis of PLA-(β-blocker) with [R₂Ga(μ-β-blocker)]₂ catalytic centers.

Drug-Initiated Synthesis of Polymer Prodrugs: Combining Simplicity and Efficacy in Drug Delivery

In the field of nanomedicine, the global trend over the past few years has been toward the design of highly sophisticated drug delivery systems with active targeting and/or imaging capabilities, as well as responsiveness to various stimuli to increase their therapeutic efficacy. However, providing sophistication generally increases complexity that could be detrimental in regards to potential pharmaceutical development. An emerging concept to design efficient yet simple drug delivery systems, termed the "drug-initiated" method, consists of growing short polymer chains from drugs in a controlled fashion to yield well-defined drug-polymer prodrugs. These materials are obtained in a reduced amount of synthetic steps and can be self-assembled into polymer prodrug nanoparticles, be incorporated into lipid nanocarriers or be used as water-soluble polymer prodrugs. This Perspective article will capture the recent achievements from the "drug-initiated" method and highlight the great biomedical potential of these materials.

Hydroxyethyl starch-10-hydroxy camptothecin conjugate: synthesis, pharmacokinetics, cytotoxicity and pharmacodynamics research

10-hydroxy camptothecin (10-HCPT) is an antitumor agent effective in the treatment of several solid tumors but its use is hampered by poor water solubility, low lactone stability, short plasma half-life and dose-limiting toxicity. In this study, 10-HCPT-hydroxyethyl starch (HES) conjugate was prepared to overcome these limits of 10-HCPT. The solubility of 10-HCPT conjugate was 0.72 mg/ml, about 100 times to free 10-HCPT. The 10-HCPT conjugate showed good sustained release effect in phosphate-buffered saline (PBS), rat plasma and liver homogenate. Meanwhile, 10-HCPT-HES conjugate achieved much lower IC50 and higher cytotoxicity effects than the free 10-HCPT on Hep-3B liver cancer cells. The pharmacokinetics results of 10-HCPT-HES conjugate demonstrated that the biological half-life of 10-HCPT was increased from 10 min to 4.38 h and the bioavailability was 40 times higher than the commercial 10-HCPT injection. The pharmacodynamics results indicated that 10-HCPT-HES conjugate had a better antitumor efficiency against nude mouse with Hep-3B tumor than the commercial 10-HCPT injection, and the inhibition ratio of tumor was 83.9 and 27.8%, respectively, at the same administration dosage. These findings suggest that 10-HCPT-HES conjugate is a promising drug delivery system providing improved long circulating effect, greater stability and better antitumor effect.

Fabrication and optimization of camptothecin loaded Eudragit S 100 nanoparticles by Taguchi L4 orthogonal array design

Introduction:

The objective of this investigation was to design and optimize the experimental conditions for the fabrication of camptothecin (CPT) loaded Eudragit S 100. Nanoparticles, and to understand the effect of various process parameters on the average particles size, particle size uniformity and surface area of the prepared polymeric nanoparticles using Taguchi design.

Materials and Methods:

CPT loaded Eudragit S 100 nanoparticles were prepared by nanoprecipitation method and characterized by particles size analyzer. Taguchi orthogonal array design was implemented to study the influence of seven independent variables on three dependent variables. Eight experimental trials involving seven independent variables at higher and lower levels were generated by design expert.

Results:

Factorial design result has shown that (a) except, β-cyclodextrin concentration all other parameters do not significantly influenced the average particle size (R1); (b) except, sonication duration and aqueous phase volume, all other process parameters significantly influence the particle size uniformity; (c) all the process parameters does not significantly influence the surface area.

Conclusion:

The R1, particle size uniformity and surface area of the prepared drug-loaded polymeric nanoparticles were found to be 120 nm, 0.237 and 55.7 m² /g and the results were good correlated with the data generated by the Taguchi design method.

Shape Control in Engineering of Polymeric Nanoparticles for Therapeutic Delivery

Nanoparticle-mediated delivery of therapeutics holds great potential for the diagnosis and treatment of a wide range of diseases. Significant advances have been made in the design of new polymeric nanoparticle carriers through modulation of their physical and chemical structures and biophysical properties. Nanoparticle shape has been increasingly proposed as an important attribute dictating their transport properties in biological milieu. In this review, we highlight three major methods for preparing polymeric nanoparticles that allow for exquisite control of particle shape. Special attention is given to various approaches to controlling nanoparticle shape by tuning copolymer structural parameters and assembly conditions. This review also provides comparisons of these methods in terms of their unique capabilities, materials choices, and specific delivery cargos, and summarizes the biological effects of nanoparticle shape on transport properties at the tissue and cellular levels.

Redox-Responsive Self-Assembled Chain-Shattering Polymeric Therapeutics

We report the design and development of redox-responsive chain-shattering polymeric therapeutics (CSPTs). CSPTs were synthesized by condensation polymerization and further modified with poly(ethylene glycol) (PEG) via "Click" reaction. Size-controlled CSPT nanoparticles (NPs) were formed through nanoprecipitation with high drug loading (up to 18%); the particle size increased in a concentration dependent manner. Drug release from particles was well controlled over 48 h upon redox triggering. The anticancer efficacy of the CSPT NPs was validated both in vitro and in vivo.

Formation of nanoparticles by cooperative inclusion between (S)-camptothecin-modified dextrans and β-cyclodextrin polymers

Novel (S)-camptothecin–dextran polymers were obtained by “click” grafting of azide-modified (S)-camptothecin and alkyne-modified dextrans. Two series based on 10 kDa and 70 kDa dextrans were prepared with a degree of substitution of (S)-camptothecin between 3.1 and 10.2%. The binding properties with β-cyclodextrin and β-cyclodextrin polymers were measured by isothermal titration calorimetry and fluorescence spectroscopy, showing no binding with β-cyclodextrin but high binding with β-cyclodextrin polymers. In aqueous solution nanoparticles were formed from association between the (S)-camptothecin–dextran polymers and the β-cyclodextrin polymers.

Enzymatic polymerization of cyclic monomers in ionic liquids as a prospective synthesis method for polyesters used in drug delivery systems

Biodegradable or bioresorbable polymers are commonly used in various pharmaceutical fields (e.g., as drug delivery systems, therapeutic systems or macromolecular drug conjugates). Polyesters are an important class of polymers widely utilized in pharmacy due to their biodegradability and biocompatibility features. In recent years, there has been increased interest in enzyme-catalyzed ring-opening polymerization (e-ROP) of cyclic esters as an alternative method of preparation of biodegradable or bioresorbable polymers. Ionic liquids (ILs) have been presented as green solvents in enzymatic ring-opening polymerization. The activity, stability, selectivity of enzymes in ILs and the ability to catalyze polyester synthesis under these conditions are discussed. Overall, the review demonstrates that e-ROP of lactones or lactides could be an effective method for the synthesis of useful biomedical polymers.

Lactide polymerization catalyzed by Mg and Zn diketiminate complexes with flexible ligand frameworks

Diketimine ligands bearing N-benzyl, N-9-anthrylmethyl and N-mesitylmethyl substituents (nacnac(Bn)H, nacnac(An)H, and nacnac(Mes)H) were prepared from condensation of the amine with either acetyl acetone or its ethylene glycol monoketal. Chlorination with N-chlorosuccinimide in the 3-position yielded Clnacnac(Bn)H and Clnacnac(An)H. The ligands were reacted with Zn(TMSA)2 (TMSA = N(SiMe3)2) to yield nacnac(An)Zn(TMSA) and Clnacnac(Bn)Zn(TMSA). Protonation with isopropanol afforded nacnac(An)ZnOiPr and Clnacnac(Bn)ZnOiPr. Reaction of the diketimines with Mg(TMSA)2 afforded nacnac(An)Mg(TMSA), nacnac(Mes)Mg(TMSA), Clnacnac(Bn)Mg(TMSA) and Clnacnac(An)Mg(TMSA). Subsequent protonation with tert-butanol produced nacnac(Mes)MgOtBu and Clnacnac(Bn)MgOtBu, but only decomposition was observed with N-anthrylmethyl substituents. Most complexes were characterized by X-ray diffraction studies. TMSA complexes were monomeric and alkoxide complexes dimeric in the solid state. All alkoxide complexes, as well as nacnac(An)Mg(TMSA)/BnOH and Clnacnac(An)Mg(TMSA)/BnOH were moderately to highly active in rac-lactide polymerization (90% conversion in 30 s to 3 h). nacnac(An)ZnOiPr produced highly heterotactic polymers (P(r) = 0.90), Clnacnac(Bn)MgOtBu/BnOH produced slightly isotactic polymers at -30 °C (P(r) = 0.43), and all other catalysts produced atactic polymers with a slight heterotactic bias.

Doxorubicin conjugate of poly(ethylene glycol)-block-polyphosphoester for cancer therapy

Polyphosphoesters with repeating phosphoester linkages in the backbone can be easily functionalized, are biodegradable and potentially biocompatible, and may be potential candidates as polymer carriers of drug conjugates. Here, the efficacy of a polyphosphoester drug conjugate as an anticancer agent in vivo is assessed for the first time. With controlled synthesis, doxorubicin conjugated to poly(ethylene glycol)-block-polyphosphoester (PPEH-DOX) via labile hydrazone bonds form spherical nanoparticles in aqueous solution with an average diameter of ≈60 nm. These nanoparticles are effectively internalized by MDA-MB-231 breast cancer cells and release the conjugated doxorubicin in response to the intracellular pH of endosomes and lysosomes, resulting in significant antiproliferative activity in cancer cells. Compared with free doxorubicin injection, PPEH-DOX injection exhibits much longer circulation behavior in the plasma of mice and leads to enhanced drug accumulation in tumor cells. In an MDA-MB-231 xenograft murine model, inhibition of tumor growth with systemic delivery of PPEH-DOX nanoparticles is more pronounced compared with free doxorubicin injection, suggesting the potential of polyphosphoesters as carriers of drug conjugates in cancer therapy.

Anticancer Camptothecin-N-Poly(lactic acid) Nanoconjugates with Facile Hydrolysable Linker

We report a strategy of conjugating CPT to the terminal carboxylate group of polylactide (PLA) with a facile hydrolysable amino ester linker via a controlled polymerization method. The obtained CPT-N-PLA conjugates were able to self-assemble into 50-100 nanometer-sized conjugates (NCs) with desired in vitro physicochemical properties and showed enhanced in vivo therapeutic efficacy against Lewis lung carcinoma (LLC) induced in C57BL/6 mice.

Redox-responsive, core-cross-linked micelles capable of on-demand, concurrent drug release and structure disassembly

We developed camptothecin (CPT)-conjugated, core-cross-linked (CCL) micelles that are subject to redox-responsive cleavage of the built-in disulfide bonds, resulting in disruption of the micellar structure and rapid release of CPT. CCL micelles were prepared via coprecipitation of disulfide-containing CPT-poly(tyrosine(alkynyl)-OCA) conjugate and monomethoxy poly(ethylene glycol)-b-poly(tyrosine(alkynyl)-OCA), followed by cross-linking of the micellar core via azide-alkyne click chemistry. CCL micelles exhibited excellent stability under physiological conditions, while they underwent rapid dissociation in reduction circumstance, resulting in burst release of CPT. These redox-responsive CCL micelles showed enhanced cytotoxicity against human breast cancer cells in vitro.

PEG-Polypeptide Dual Brush Block Copolymers: Synthesis and Application in Nanoparticle Surface PEGylation

Amphiphilic polypeptide-containing hybrid dual brush block copolymers with controlled molecular weights and narrow molecular weight distributions were synthesized in one pot via ring-opening metathesis polymerization of sequentially added norbornyl-PEG and N-(2-((trimethylsilyl)amino)ethyl)-5-norbornene-endo-2,3-dicarboximide (M1) followed by ring-opening polymerization of amino acid N-carboxyanhydrides. Polylactide nanoparticles coated with these am phiphilic dual brush block copolymers showed significantly improved stability in PBS solution compared to those coated with amphiphilic linear block copolymers such as PEG-polylactide and PEG-polypeptides.

Evaluation of the cytotoxic effect of camptothecin solid lipid nanoparticles on MCF7 cells

Camptothecin (CPT) and its analogs exhibit remarkable anti-tumor activity, due to their ability to inhibit DNA topoisomerase I. However, its use is limited by the lack of solubility and stability of the active lactone form. An attractive alternative is the encapsulation of CPT within liposomes. In this study, CPT was incorporated into solid lipid nanoparticles (SLN) based on the triglyceride, Compritol 888 ATO, using supercritical fluid technology without requiring the use of harmful solvents. This drug delivery system was characterized and its cytotoxicity effect was evaluated by measuring MCF7 and MCF10A cell viability as a function of drug loading during a 48-h treatment. Results showed that after 10 h of treatment, MCF7 cells displayed an IC50 of 0.23±0.034 μM at a 1:5 (CPT:SLN) loading and 0.22±0.027 μM at a 1:10 loading, whereas MCF10A cells displayed an IC50 of 0.40±0.036 μM at 1:5 and 0.60±0.063 μM at 1:10. On the other hand, the IC50 of free CPT was 0.57±0.035 μM and 1.07±0.077 μM for MCF7 and MCF10A cells, respectively. Cellular uptake and retention measurements in both cells displayed a two-fold increase when using the SLN formulation. The results from this study showed that the cytotoxic effects of CPT in a SLN formulation improved when compared with those seen with free CPT. The results of this study showed that delivery of CPT as a SLN formulation could be a promising strategy for enhancing its chemotherapeutic effects.

Erythrocyte membrane-cloaked polymeric nanoparticles for controlled drug loading and release

Aim: Polymeric nanoparticles (NPs) cloaked by red blood cell membrane (RBCm) confer the combined advantage of both long circulation lifetime and controlled drug release. The authors carried out studies to gain a better understanding of the drug loading, drug-release kinetics and cell-based efficacy of RBCm-cloaked NPs. Materials & methods: Two strategies for loading doxorubicin into the RBCm-cloaked NPs were compared: physical encapsulation and chemical conjugation. In vitro efficacy was examined using the acute myeloid leukemia cell line, Kasumi-1. Results: It was found that the chemical conjugation strategy resulted in a more sustained drug release profile, and that the RBCm cloak provided a barrier, retarding the outward diffusion of encapsulated drug molecules. It was also demonstrated that RBCm-cloaked NPs exhibit higher toxicity in comparison with free doxorubicin. Conclusion: These results indicate that the RBCm-cloaked NPs hold great promise to become a valuable drug-delivery platform for the treatment of various diseases such as blood cancers.

Original submitted 27 February 2012; Revised submitted 27 August 2012; Published online 14 February 2013

Chain-shattering polymeric therapeutics with on-demand drug-release capability

Design of smart polymeric therapeutics

We designed and synthesized trigger-responsive chain-shattering polymeric therapeutics (CSPTs) via condensation polymerization of a UV-or hydrogen peroxide-responsive domain and a bisfunctional drug as co-monomers. CSPTs have precisely controlled molecular composition and unique chain-shattering type of drug release mechanism. Drug release kinetics can be precisely controlled by means of the trigger treatment. Chemotherapeutic-containing CSPTs showed trigger-responsive in vitro and in vivo antitumor efficacy.

Drug-initiated ring-opening polymerization of O-carboxyanhydrides for the preparation of anticancer drug-poly(O-carboxyanhydride) nanoconjugates

We report a novel synthetic strategy of polymer-drug conjugates for nanoparticulate drug delivery: hydroxyl-containing drug (e.g., camptothecin, paclitaxel, doxorubicin and docetaxel) can initiate controlled polymerization of phenyl O-carboxyanhydride (Phe-OCA) to afford drug-poly(Phe-OCA) conjugated nanoparticles, termed drug-PheLA nanoconjugates (NCs). Our new NCs have well-controlled physicochemical properties, including high drug loading, quantitative drug loading efficiency, controlled particle size with narrow particle size distribution, and sustained drug release profile over days without "burst" release effect as observed in conventional polymer/drug encapsulates. Compared with polylactide NCs, the PheLA NCs have increased noncovalent hydrophobic interchain interactions and thereby result in remarkable stability in human serum with negligible particle aggregation. Such distinctive properties can reduce the premature disassembly of NCs upon dilution in the bloodstream and prolong NCs' in vivo circulation with the enhancement of intratumoral accumulation of NCs, which has a bearing on therapeutic effectiveness.

Polymeric Nanomedicines Based on Poly(lactide) and Poly(lactide-co-glycolide)

Small molecule chemotherapeutics often have undesired physiochemical and pharmacological properties, such as low solubility, severe side effect and narrow therapeutic index. To address these challenges, polymeric nanomedicine drug delivery technology has been routinely employed, in particular with the use of biodegradable and biocompatible polyesters, such as poly(lactide) (PLA) and poly(lactide-co-glycolide) (PLGA). Here we review the development and use of PLA and PLGA for the delivery of chemotherapeutic agents in the forms of polymer-drug conjugates and nanoconjugates.

Synthesis of water-soluble camptothecin-polyoxetane conjugates via click chemistry

Water-soluble camptothecin (CPT)-polyoxetane conjugates were synthesized using a clickable polymeric platform P(EAMO) that was made by polymerization of acetylene-functionalized 3-ethyl-3-(hydroxymethyl)oxetane (i.e., EAMO). CPT was first modified with a linker 6-azidohexanoic acid via an ester linkage to yield CPT-azide. CPT-azide was then click coupled to P(EAMO) in dichloromethane using bromotris(triphenylphosphine)copper(I)/N,N-diisopropylethylamine. For water solubility and cytocompatibility improvement, methoxypolyethylene glycol azide (mPEG-azide) was synthesized from mPEG 750 g mol(-1) and click grafted using copper(II) sulfate and sodium ascorbate to P(EAMO)-g-CPT. (1)H NMR spectroscopy confirmed synthesis of all intermediates and the final product P(EAMO)-g-CPT/PEG. CPT was found to retain its therapeutically active lactone form. The resulting P(EAMO)-g-CPT/PEG conjugates were water-soluble and produced dose-dependent cytotoxicity to human glioma cells and increased γ-H2AX foci formation, indicating extensive cell cycle-dependent DNA damage. Altogether, we have synthesized CPT-polymer conjugates able to induce controlled toxicity to human cancer cells.

Synthesis of water-soluble poly(α-hydroxy acids) from living ring-opening polymerization of O-benzyl-L-serine carboxyanhydrides

O-benzyl-L-serine carboxyanhydrides were synthesized via diazotization of O-benzyl-L-serine with sodium nitrite in aqueous sulfuric acid solution followed by cyclization of the resulting serine-based α-hydroxy acid with phosgene. Degradable, water-soluble poly(α-hydroxy acids) bearing pendant hydroxyl groups were readily prepared under mild conditions via ring-opening polymerization of O-benzyl-L-serine carboxyanhydrides followed by removal of the benzyl group and showed excellent cell compatibility, suggesting their potential being used as novel materials in constructing drug delivery systems and as hydrogel scaffolds for tissue engineering applications.

Immunosuppressive Activity of Size-Controlled PEG-PLGA Nanoparticles Containing Encapsulated Cyclosporine A

We encapsulated cyclosporine A (CsA) in poly(ethylene glycol)-b-poly(d,l-lactide-co-glycolide) (PEG-PLGA) nanoparticles (NPs) by nanoprecipitation of CsA and PEG-PLGA. The resulting CsA/PEG-PLGA-NPs were <100 nm in diameter with a narrow particle size distribution. The NP size could be controlled by tuning the polymer concentration, solvent, or water/solvent ratio during formulation. The PEGylated NPs maintained non-aggregated in salt solution. Solid NPs lyoprotected with bovine serum albumin were prepared for the convenience of storage and transportation. The release kinetics of CsA (55.6% released on Day 1) showed potential for maintaining therapeutic CsA concentrations in vivo. In T-cell assays, both free CsA and CsA/PEG-PLGA-NPs suppressed T-cell proliferation and production of inflammatory cytokines dose dependently. In a mixed lymphocyte reaction assay, the IC(50) values for free CsA and CsA/PEG-PLGA-NPs were found to be 30 and 35 ng/mL, respectively. This nanoparticulate CsA delivery technology constitutes a strong basis for future targeted delivery of immunosuppressive drugs with improved efficiency and potentially reduced toxicity.

Drug-Initiated, Controlled Ring-Opening Polymerization for the Synthesis of Polymer-Drug Conjugates

Paclitaxel, a polyol chemotherapeutic agent, was covalently conjugated through its 2'-OH to polylactide with 100% regioselectivity via controlled polymerization of lactide mediated by paclitaxel/(BDI-II)ZnN(TMS)(2) (BDI-II = 2-((2,6-diisopropylphenyl)amino)-4-((2,6-diisopropylphenyl)imino)-2-pentene). The steric bulk of the substituents on the N-aryl groups of the BDI ligand drastically affected the regiochemistry of coordination of the metal catalysts to paclitaxel and the subsequent ring-opening polymerization of lactide. The drug-initiated, controlled polymerization of lactide was extended, again with 100% regioselectivity, to docetaxel, a chemotherapeutic agent that is even more structurally complex than paclitaxel. Regioselective incorporation of paclitaxel (or docetaxel) to other biopolymers (i.e., poly(δ-valerolactone), poly(trimethylene carbonate), and poly(ε-caprolactone)), was also achieved through drug/(BDI-II)ZnN(TMS)(2)-mediated controlled polymerization. These drug-polylactide conjugates with precisely controlled structures are expected to be excellent building blocks for drug delivery, coating, and controlled-release applications.

Microfluidic approach for highly efficient synthesis of heparin-based bioconjugates for drug delivery

This paper demonstrates the highly efficient synthesis of amphiphilic heparin-folic acid-retinoic acid (HFR) bioconjugates with a high drug coupling ratio by a microfluidic approach. The microfluidic synthesis enabled the conjugation of 17 molecules of retinoic acid to each heparin chain with 21 possible groups for attachment after reacting for several minutes. In contrast, about 11 molecules of the drug were covalently conjugated to one heparin chain after 4 days in the bulk reaction. The microfluidic based-HFR bioconjugates readily self-assembled in aqueous media to form uniform nanoparticles, while the product from the bulk reaction formed non-uniform nanoparticles with broad size distribution. The HFR nanoparticles with high drug content effectively delivered the drug to folate receptor-positive cancer cells with superior cellular uptake and selective cytotoxicity in vitro compared to HFR nanoparticles synthesized in bulk reaction. With the ability to achieve high drug content in heparin carrier within a short reaction time, the microfluidic technique offers new alternatives for the efficient synthesis of polymer-based conjugates for drug delivery.