A stable nanoplatform for antitumor activity using PEG-PLL-PLA triblock co-polyelectrolyte

Comparison of triblock copolymeric micelles based on α- and ε-poly(L-lysine): a Cornelian choice

Due to the lack of safe carriers for the delivery of small interfering RNA (siRNA), clinical applications of nucleotide-based therapeutics have been limited. In this study, biodegradable amphiphilic triblock copolymers with tailored molecular weights for each block composed of methoxy poly(ethylene glycol) (2000 g/mol), poly(L-lysine) (1300 g/mol) and poly(D,L-lactic acid) (1800 g/mol) (mPEG45-α-PLL10-PLA25) were synthesized and fully characterized. The peptide synthesis was carried out on a solid phase to limit the presence of cationic charges. The arrangement and availability of cationic amino groups within a micellar vector were investigated to determine the colloidal stability as well as the predisposition of these systems to vectorize siRNAs in addition to their already known ability to improve the solubility of hydrophobic compounds. For this purpose, a triblock copolymer containing an epsilon poly(L-lysine) was synthesized similarly. Accordingly, the arrangement of the cationic segment modifies the rigidity involving a complexation constraint due to limited cationic charges available on the surface, which can compromise the efficiency of delivery into cells. In addition, the two vectors were biocompatible in different human cell lines.

Self-assembled polymeric micelles for targeted photodynamic therapy of human epidermal growth factor receptor 2 overexpressing breast cancer

Photodynamic therapy (PDT) has been extensively explored as a promising alternative therapeutic approach for many malignant tumors. However, the PDT system generally involves unsatisfactory tumor specificity and nonspecific accumulation of photosensitizers around the target cancer cells, leading to phototoxic damage to adjacent healthy normal cells. In this study, we developed pheophorbide a (Pheo a)/human epidermal growth factor receptor 2 (HER2) targeting peptide (epitope form, HLTV, PEG2-LTVSPWY)-co-conjugated methoxy poly(ethylene glycol)-block-poly(L-lysine hydrochloride) (PEG-PLL)/hyaluronic acid (HA) (P3H2) polymeric micelles via a self-assembly method for HER2-targeted PDT treatment for breast cancer, thereby enhancing the PDT efficacy. The synthesized P3H2 polymeric micelles were spherical, with an average diameter of 125.7 ± 21.2 nm in an aqueous solution. The results ofin vitrocytotoxicity assays demonstrated that the P3H2 polymeric micelles significantly improved PDT efficacy on the SK-BR-3 cells due to the enhanced targeting ability. In addition, PDT treatment using the P3H2 polymeric micelles effectively killed breast cancer cells by inducing higher intracellular reactive oxygen species generation and apoptotic cell death. In particular, the three-dimensional cell culture model proved the synergistic PDT efficacy using P3H2 polymeric micelles on the SK-BR-3 cells. Based on these results, the PDT treatment using P3H2 polymeric micelles can serve as a highly effective therapeutic modality for breast cancer.

An On-Demand pH-Sensitive Nanocluster for Cancer Treatment by Combining Photothermal Therapy and Chemotherapy

Combination therapy is considered to be a promising strategy for improving the therapeutic efficiency of cancer treatment. In this study, an on-demand pH-sensitive nanocluster (NC) system was prepared by the encapsulation of gold nanorods (AuNR) and doxorubicin (DOX) by a pH-sensitive polymer, poly(aspartic acid-graft-imidazole)-PEG, to enhance the therapeutic effect of chemotherapy and photothermal therapy. At pH 6.5, the NC systems formed aggregated structures and released higher drug amounts while sustaining a stable nano-assembly, structured with less systemic toxicity at pH 7.4. The NC could also increase antitumor efficacy as a result of improved accumulation and release of DOX from the NC system at pHex and pHen with locally applied near-infrared light. Therefore, an NC system would be a potent strategy for on-demand combination treatment to target tumors with less systemic toxicity and an improved therapeutic effect.

Evaluation and comparison of cytotoxicity, genotoxicity, and apoptotic effects of poly-l-lysine/plasmid DNA micro- and nanoparticles

The principal impediment to gene therapy is the development of efficient, nontoxic gene carriers that can handle and deliver foreign genetic materials into various cell types, including healthy and cancerous cells. Poly-l-lysine (PLL) polymers are one of the most favorable gene carriers among nonviral vectors, and PLL had low transfection and safety issues. The purpose of this study was to measure cellular toxicity, DNA damage, and apoptotic effects of PLL nanoparticles. Neuro2A mammalian cells were cultured and exposed to PLL/DNA complexes at different polymer/DNA ratios ( C/ P ratio 2 and 6) for 24 h. To evaluate metabolic activity, genotoxicity, and apoptotic influences of PLL nanoparticle, the following experimental methods were employed, in order: 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), DNA damage (COMET analysis) assay, and sub-G1 peak apoptosis assay. Our data indicate that toxicity is concentration dependent and a high concentration of polymer declined the metabolic activity. In addition, largest complexes ( C/ P 6 in HEPES buffered saline buffer) have slighter negative impact on metabolic activity. In agreement with our cytotoxicity data, apoptotic assay result represented that increase in size of PLL/DNA complexes decrease the number of apoptotic cells. Also, there was a remarkable increase in percent tail DNA of Neuro2A cells treated with higher concentration of PLL and its polyplexes. The present study demonstrated that PLL/DNA complexes caused cytotoxic, apoptotic, and genotoxic effects in a dose-dependent and weight ratio-dependent manner, which also affected the size of polyplexes.

Co-delivery of d-(KLAKLAK)2 peptide and doxorubicin using a pH-sensitive nanocarrier for synergistic anticancer treatment

Currently, one of the most important challenges in the development of nanotechnology-based anticancer treatments is the failure of nanoparticles to escape from the endo-lysosomal compartment.

"Grafting-from" synthesis and characterization of poly (2-ethyl-2-oxazoline)-b-poly (benzyl L-glutamate) micellar nanoparticles for potential biomedical applications

Introduction: Recent advances in the field of poly (2-oxazolines) as bio-inspired synthetic pseudopeptides have proven their potential biomedical applications such as drug delivery and tissue engineering. Methods: In order to fabricate a biodegradable micellar nanoparticle of poly (2-ethyl 2-oxazoline)-b-poly (benzyl L-glutamate) or pEOx-b-pBLG, "grafting-from" synthesis approach was used involving consecutive steps of cationic ring-opening polymerization of 2-ethyl-2-oxazoline, amine functionalization of pEOx using 1-Boc-piperazine and N-carboxyanhydride polymerization of γ-benzyl- L-glutamate. Following hydrolysis of the copolymer, the protecting γ-benzyl groups were removed yielding a double-hydrophilic block ionomer of pEOx-b-poly (L-glutamic acid). The polymers were characterized by FTIR, 1H-NMR, size exclusion chromatography and differential scanning calorimetry (DSC). Aqueous assembly of the polymers was investigated by pyrene assay, dynamic light scattering, and transmission electron microscopy. MTT cytotoxicity assay was also performed to determine the cytocompatibility in various tumor cell lines. Results: The polymeric micelles presented a uni-modal size distribution with mean hydrodynamic diameter of 149.8 ± 10.6 nm and critical aggregation concentration of 60 µg/mL. The average molecular weight of pEOx increased from ~ 14 to 20 kDa for pEOx-b-poly (L-glutamic acid) as determined by light scattering (Debye plot), indicating a successful copolymerization. MTT assay showed little to no practical cytotoxicity at concentrations below 1 mg/mL. Conclusion: Multi-step synthesis of pEOx-b-pBLG and subsequent alkaline hydrolysis were performed to obtain the block ionomer pEOx-b-poly (L-glutamic acid). Both pEOx-based copolymers can be considered for various potential applications such as loading and delivery of drugs, genes, and contrast agents either by chemical conjugation or physical loading.

A charge-reversible nanocarrier using PEG-PLL (-g-Ce6, DMA)-PLA for photodynamic therapy

A polyelectrolyte nanoparticle composed of PEG-PLL(-g-Ce6, DMA)-PLA was developed for nanomedicinal application in photodynamic therapy. These nanoparticles formed stable aggregates through the hydrophobic interaction of poly(lactic acid) and demonstrated pH-dependent behaviors such as surface charge conversion and enhanced cellular uptake at acidic pH, resulting in improved phototoxicity. In vivo animal imaging revealed that the prepared PEG-PLL(-g-Ce6, DMA)-PLA nanoparticles effectively accumulated at the targeted tumor site through enhanced permeability and retention effects. Reversible surface charge for PEG-PLL (-g-Ce6, DMA)-PLA nanoparticles allows the nanoparticles to escape the immune system and concentrate on the tumor tissue. Tumor growth in the nude mice treated with the nanoparticles decreased significantly and the hydrophobic interaction in the poly(lactic acid) block could allow the incorporation of multiple drugs. Therefore, the PEG-PLL(-g-Ce6, DMA)-PLA nanoparticles could have considerable potential as a nanomedicinal platform for photodynamic therapy.