Recent advances in PEG–PLA block copolymer nanoparticles

Due to their small particle size and large and modifiable surface, nanoparticles have unique advantages compared with other drug carriers. As a research focus in recent years, polyethylene glycol–polylactic acid (PEG–PLA) block copolymer and its end-group derivative nanoparticles can enhance the drug loading of hydrophobic drugs, reduce the burst effect, avoid being engulfed by phagocytes, increase the circulation time of drugs in blood, and improve bioavailability. Additionally, due to their smaller particle size and modified surface, these nanoparticles can accumulate in inflammation or target locations to enhance drug efficacy and reduce toxicity. Recent advances in PEG–PLA block copolymer nanoparticles, including the synthesis of PEG–PLA and the preparation of PEG–PLA nanoparticles, were introduced in this study, in particular the drug release and modifiable characteristics of PEG–PLA nanoparticles and their application in pharmaceutical preparations

Preparation of poly(ethylene glycol)/polylactide hybrid fibrous scaffolds for bone tissue engineering

Polylactide (PLA) electrospun fibers have been reported as a scaffold for bone tissue engineering application, however, the great hydrophobicity limits its broad application. In this study, the hybrid amphiphilic poly(ethylene glycol) (PEG)/hydrophobic PLA fibrous scaffolds exhibited improved morphology with regular and continuous fibers compared to corresponding blank PLA fiber mats. The prepared PEG/PLA fibrous scaffolds favored mesenchymal stem cell (MSC) attachment and proliferation by providing an interconnected porous extracellular environment. Meanwhile, MSCs can penetrate into the fibrous scaffold through the interstitial pores and integrate well with the surrounding fibers, which is very important for favorable application in tissue engineering. More importantly, the electrospun hybrid PEG/PLA fibrous scaffolds can enhance MSCs to differentiate into bone-associated cells by comprehensively evaluating the representative markers of the osteogenic procedure with messenger ribonucleic acid quantitation and protein analysis. MSCs on the PEG/PLA fibrous scaffolds presented better differentiation potential with higher messenger ribonucleic acid expression of the earliest osteogenic marker Cbfa-1 and mid-stage osteogenic marker Col I. The significantly higher alkaline phosphatase activity of the PEG/PLA fibrous scaffolds indicated that these can enhance the differentiation of MSCs into osteoblast-like cells. Furthermore, the higher messenger ribonucleic acid level of the late osteogenic differentiation markers OCN (osteocalcin) and OPN (osteopontin), accompanied by the positive Alizarin red S staining, showed better maturation of osteogenic induction on the PEG/PLA fibrous scaffolds at the mineralization stage of differentiation. After transplantation into the thigh muscle pouches of rats, and evaluating the inflammatory cells surrounding the scaffolds and the physiological characteristics of the surrounding tissues, the PEG/PLA scaffolds presented good biocompatibility. Based on the good cellular response and excellent osteogenic potential in vitro, as well as the biocompatibility with the surrounding tissues in vivo, the electrospun PEG/PLA fibrous scaffolds could be one of the most promising candidates in bone tissue engineering

Biological properties of Pegylated PLA (PLA-PEG-PLA) and its capability for intracellular delivery of poor soluble peptide drug, gramicidin

Poly lactic acid-co-poly ethylene glycol-co-Poly lactic acid (PLA-PEG-PLA) co-polymer was synthesized and after determination of its biological properties was used for intracellular delivery of poor soluble peptide drug, gramicidin. Toxicity of this polymer on LNCaP cell line was determined by MTT assay. Treatment of cells with fluorescein isothiocyanate (FITC) loaded nanoparticles and fluorescence microscopy indicates ability of this carrier for intracellular delivery. PLA-PEG-PLA nanoparticles containing poor soluble peptide drug, gramicidin, was prepared by solvent evaporation method. In order to confirm loading of gramicidin on PLA-PEG-PLA nanoparticles, FT-IR, spectrofluoremeteric, circular dichroism (CD), and scanning electron microscopy (SEM) studies were carried out. Our studies revealed treatment of prostate cancer cell line, LNCaP, with gramicidin loaded nanoparticles was more effective than gramicidin alone in killing cancer cells

Nanoparticle mediated oral delivery of insulin

The oral delivery of therapeutic compounds, from small molecules to proteins, is one of the most desirable routes of administration. Its advantages reside in low cost, patient compliance and ease of use. The major challenge associated to such a delivery route is the transport through the gastrointestinal tract (GIT). In the case of complex and fragile molecules such as proteins, this particular step is the source of multiple challenges. Among the approaches developed to protect the therapeutic compound, the use of polymeric carriers is the most promising. We developed biocompatible and biodegradable polymersomes formed by the self assembly of amphiphilic copolymers in water. The copolymers we used are a combination of the following homopolymers: poly(ethylene glycol), poly(lactic acid), poly(caprolactone) and poly(glutamic acid). The PEG-PLA or PLA blocks were prepared by ring opening bulk polymerization (ROP) using an organic catalyst, and an alcohol as initiator. The poly(glutamic acid) was prepared aside by ROP of the benzyl glutamate N-CarboxyAnhydride (NCA), followed by the deprotection of the benzyl group. The final copolymer was obtained by coupling a PEG-PLA (or PLA) to a PGluOH. Another synthesis route was explored. It consists in the preparation of a macro amine, namely PEG-PLA-(NH 2)x, used to ring open the benzyl glutamate NCA. The PEG-PLA-PGluBn is then deprotected. The polymer chains obtained by one of these two synthesis routes self assemble in basic water into well defined vesicles with diameter ranging from 70 to 100 nm. They can be loaded with insulin and orally delivered. The vesicles are progressively degraded along the GIT before transport through intestine wall and insulin is released. A full characterization of the polymers and a study of the morphology of self assemblies constitute the bulk of this work

In situ forming stereocomplexed and post-photocrosslinked acrylated star poly(ethylene glycol)-poly(lactide) hydrogels

Biodegradable acrylate end-group functionalized poly(ethylene glycol)-poly(lactide) (PEG-PLA) star block copolymer hydrogels were formed by the consecutive physical gelation through stereocomplexation of star shaped PEG-(PLLA)8 and PEG-(PDLA)8 enantiomers and UV photopolymerization. The 8-armed PEG-PLA star block copolymers were prepared by ring opening polymerization of lactide onto an amine end-group functionalized PEG with a molecular weight of 20 kg/mol using stannous octoate as a catalyst. The degree of polymerization of the PLA blocks was 12 lactyl units and the end hydroxyl groups were reacted with acryloyl chloride to give the required acrylate end groups. Aqueous solutions of enantiomeric mixtures of the PEG-(PLA)8 macromonomers formed physically crosslinked hydrogels above a critical gel concentration of 4 w/v%. Subsequent photopolymerization at 365 nm in the presence of Irgacure 2959 resulted in gels with improved mechanical properties and hydrolytic stability. With 40% polymer mass loss after 45 d in vitro, these hydrogels show excellent resistance against hydrolytic degradation and dissolution, which is believed to result from the combination of stable amide linkages between the PEG and PLA blocks and the high physical and chemical crosslink density owing to the star architecture

Radioluminescent nanoparticles for radiation-controlled release of drugs

The present work demonstrates a novel concept for intratumoral chemo-radio combination therapy for locally advanced solid tumors. For some locally advanced tumors, chemoradiation is currently standard of care. This combination treatment can cause acute and long term toxicity that can limit its use in older patients or those with multiple medical comorbidities. Intratumoral chemotherapy has the potential to address the problem of systemic toxicity that conventional chemotherapy suffers, and may, in our view, be a better strategy for treating certain locally advanced tumors. The present study proposes how intratumoral chemoradiation can be best implemented. The enabling concept is the use of a new chemotherapeutic formulation in which chemotherapy drugs (e.g., paclitaxel (PTX)) are co-encapsulated with radioluminecsnt nanoparticles (e.g., CaWO4 (CWO) nanoparticles (NPs)) within protective capsules formed by biocompatible/biodegradable polymers (e.g., poly(ethylene glycol)-poly(lactic acid) or PEG-PLA). This drug-loaded polymer-encapsulated radioluminescent nanoparticle system can be locally injected in solution form into the patient's tumor before the patient receives normal radiotherapy (e.g., 30–40 fractions of 2–3 Gy daily X-ray dose delivered over several weeks for locally advanced head and neck tumors). Under X-ray irradiation, the radioluminescent nanoparticles produce UV-A light that has a radio-sensitizing effect. These co-encapsulated radioluminescent nanoparticles also enable radiation-triggered release of chemo drugs from the polymer coating layer. The non-toxic nature (absence of dark toxicity) of this drug-loaded polymer-encapsulated radioluminescent nanoparticle (“PEG-PLA/CWO/PTX”) formulation was confirmed by the MTT assay in cancer cell cultures. A clonogenic cell survival assay confirmed that these drug-loaded polymer-encapsulated radioluminescent nanoparticles significantly enhance the cancer cell killing effect of radiation therapy. In vivo study validated the efficacy of PEG-PLA/CWO/PTX-based intratumoral chemo-radio therapy in mouse tumor xenografts (in terms of tumor response and mouse survival). Results of a small-scale NP biodistribution (BD) study demonstrate that PEG-PLA/CWO/PTX NPs remained at the tumor sites for a long period of time (> 1 month) following direct intratumoral administration. A multi-compartmental pharmacokinetic model (with rate constants estimated from in vitro experiments) predicts that this radiation-controlled drug release technology enables significant improvements in the level and duration of drug availability within the tumor (throughout the typical length of radiation treatment, i.e., > 1 month) over conventional delivery systems (e.g., PEG-PLA micelles with no co-encapsulated CaWO4, or an organic liquid, e.g., a 50:50 mixture of Cremophor EL and ethanol, as in Taxol), while it is capable of maintaining the systemic level of the chemo drug far below the toxic threshold limit over the entire treatment period. This technology thus has the potential to offer a new therapeutic option that has not previously been available for patients excluded from conventional chemoradiation protocols

Enhanced Delivery of Rituximab Into Brain and Lymph Nodes Using Timed-Release Nanocapsules in Non-Human Primates.

Tumor metastasis into the central nervous system (CNS) and lymph nodes (LNs) is a major obstacle for effective therapies. Therapeutic monoclonal antibodies (mAb) have revolutionized tumor treatment; however, their efficacy for treating metastatic tumors-particularly, CNS and LN metastases-is poor due to inefficient penetration into the CNS and LNs following intravenous injection. We recently reported an effective delivery of mAb to the CNS by encapsulating the anti-CD20 mAb rituximab (RTX) within a thin shell of polymer that contains the analogs of choline and acetylcholine receptors. This encapsulated RTX, denoted as n-RTX, eliminated lymphoma cells systemically in a xenografted humanized mouse model using an immunodeficient mouse as a recipient of human hematopoietic stem/progenitor cells and fetal thymus more effectively than native RTX; importantly, n-RTX showed notable anti-tumor effect on CNS metastases which is unable to show by native RTX. As an important step toward future clinical translation of this technology, we further analyzed the properties of n-RTX in immunocompetent animals, rats, and non-human primates (NHPs). Our results show that a single intravenous injection of n-RTX resulted in 10-fold greater levels in the CNS and 2-3-fold greater levels in the LNs of RTX, respectively, than the injection of native RTX in both rats and NHPs. In addition, we demonstrate the enhanced delivery and efficient B-cell depletion in lymphoid organs of NHPs with n-RTX. Moreover, detailed hematological analysis and liver enzyme activity tests indicate n-RTX treatment is safe in NHPs. As this nanocapsule platform can be universally applied to other therapeutic mAbs, it holds great promise for extending mAb therapy to poorly accessible body compartments

Sustained delivery and molecular targeting of a therapeutic monoclonal antibody to metastases in the central nervous system of mice.

Approximately 15-40% of all cancers develop metastases in the central nervous system (CNS), yet few therapeutic options exist to treat them. Cancer therapies based on monoclonal antibodies are widely successful, yet have limited efficacy against CNS metastases, owing to the low levels of the drug reaching the tumour site. Here, we show that the encapsulation of rituximab within a crosslinked zwitterionic polymer layer leads to the sustained release of rituximab as the crosslinkers are gradually hydrolysed, enhancing the CNS levels of the antibody by approximately tenfold with respect to the administration of naked rituximab. When the nanocapsules were functionalized with CXCL13-the ligand for the chemokine receptor CXCR5, which is frequently found on B-cell lymphoma-a single dose led to improved control of CXCR5-expressing metastases in a murine xenograft model of non-Hodgkin lymphoma, and eliminated lymphoma in a xenografted humanized bone marrow-liver-thymus mouse model. Encapsulation and molecular targeting of therapeutic antibodies could become an option for the treatment of cancers with CNS metastases

Use of single-chain antibody derivatives for targeted drug delivery

Single-chain antibodies (scFvs), which contain only the variable domains of full-length antibodies, are relatively small molecules that can be used for selective drug delivery. In this review, we discuss how scFvs help improve the specificity and efficiency of drugs. Small interfering RNA (siRNA) delivery using scFv-drug fusion peptides, siRNA delivery using scFv-conjugated nanoparticles, targeted delivery using scFv-viral peptide-fusion proteins, use of scFv in fusion with cell-penetrating peptides for effective targeted drug delivery, scFv-mediated targeted delivery of inorganic nanoparticles, scFv-mediated increase of tumor killing activity of granulocytes, use of scFv for tumor imaging, site-directed conjugation of scFv molecules to drug carrier systems, use of scFv to relieve pain and use of scFv for increasing drug loading efficiency are among the topics that are discussed here. © 2016, University of Michigan. All rights reserved