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Journal of controlled release [journal]
- Dual Fluorescent HPMA Copolymers for Passive Tumor Targeting with pH-Sensitive Drug Release II: Impact of Release Rate on Biodistribution. [JOURNAL ARTICLE]
- J Control Release 2013 May 19.
In recent years, polymer drug carriers based on N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers with pH-triggered drug release have shown enhanced uptake in solid tumors and excellent antitumor activity. Here, the impact of the structure of the acid-labile spacer between the drug and the polymer carrier on the biodistribution of both the drug and the carrier was studied using in vivo noninvasive multispectral optical imaging of dual fluorescently labeled HPMA copolymers. Five different spacers containing a pH-sensitive hydrazone bond were synthesized and used to combine a fluorescent model drug with a polymer backbone, conjugated with another non-releasable fluorescent dye. Two copolymers differing in polymer chain structure (linear and star-like) and molecular weight (30 and 200 kDa) were used to distinguish between carriers with molecular weights above and below the limit for renal filtration. The rate of model drug release from the conjugates was determined in vitro. The biodistributions of the six most promising conjugates were investigated in vivo in athymic nude mice inoculated with human colon carcinoma xenograft. The structure of the spacer in the vicinity of the hydrazone bond significantly influenced the release rate of the model drug. The slow release rate of a pyridyl group bearing spacer resulted in a greater amount of the model drug being transported to the tumor, which was independent of the carrier structure. The results of this study emphasize the importance of careful selection of the structure and appropriate spacer when designing polymer conjugates intended for passive tumor targeting.
- Bacterial-directed enzyme prodrug therapy. [JOURNAL ARTICLE]
- J Control Release 2013 May 17.
Current conventional treatments for cancer lack tumour selectivity resulting in the destruction of healthy tissue and severe adverse effects to the patient in addition to limiting the administration dose and efficacy. Hence, it is imperative that we seek alternative approaches to treat cancer that localise therapeutic agents to the site of the tumour and spare normal tissue. The use of bacteria in cancer therapy represents one such approach. Bacteria were first used as anti-cancer agents over a century ago. Today, this field has re-emerged from the past and is progressing at a rapid rate. Bacteria are used as anticancer agents either alone or in combination with conventional treatments and have been armed with an arsenal of therapeutic genes, which enhance their efficacy. Bacterial directed enzyme prodrug therapy (BDEPT) is one of the most promising approaches, which harnesses the tumour-specific location of bacteria to locally activate systemically administered 'prodrugs' within the tumour in order to induce selective tumour destruction. BDEPT is a relatively new concept. It was originally conceived more than 10 years ago but it is only until recently that we witness a surge in activity in this field. In this review, we provide a full account of developments in the field of BDEPT since its inception. We share technical knowhow and discuss optimization strategies for vector and enzyme combinations, provide a clear view of the research landscape and suggest possible directions for the field.
- Protocells for DNA cargo delivery to the spinal cord. [Editorial]
- J Control Release 2013 Jun 10; 168(2):238.
- Delivery of definable numbers of PLGA microparticles within embryoid bodies. [Editorial]
- J Control Release 2013 May 28; 168(1):103.
- VEGF-releasing biodegradable nanospheres administered by craniotomy: A novel therapeutic approach in the APP/Ps1 mouse model of Alzheimer's disease. [JOURNAL ARTICLE]
- J Control Release 2013 May 16.
This study attempts to develop a novel nanotechnology-based strategy to deliver vascular endothelial growth factor (VEGF) to the brain, as a possible therapeutic approach for AD. For this purpose, VEGF was encapsulated in biodegradable poly(lactic-co-glycolic acid) (PLGA) nanospheres (VEGF-NS). The nanosphere particle size was about 200 nm, with a narrow size distribution, and the zeta potential around -30 mV. The encapsulation efficiency of VEGF was 44.06 ± 5.61%, showing a biphasic release profile in vitro. The biological activity and neuroprotective effect of encapsulated VEGF were investigated in neuronal cell cultures, confirming the neuronal proliferative effect and the protection against Aβ42 induced neurotoxicity. In vivo studies were carried out in amyloid precursor protein/presenilin-1 (APP/Ps1) mice administering VEGF-NS through minimally invasive craniotomy. The results obtained showed that VEGF-NS were able to improve behavioral deficits, decrease Aβ deposits and promote angiogenesis, as well as reduce neuronal loss and cerebrovascular abnormalities. Furthermore, their ability to protect neuronal cultures against neuroinflammation induced by LPS provides new insight for future therapeutic approaches in other neurodegenerative disorders.
- A permeation enhancer for increasing transport of therapeutic macromolecules across the intestine. [JOURNAL ARTICLE]
- J Control Release 2013 May 14.
Delivery of therapeutic macromolecules is limited by the physiological limitations of the gastrointestinal tract including poor intestinal permeability, low pH and enzymatic activity. Several permeation enhancers have been proposed to enhance intestinal permeability of macromolecules; however their utility is often hindered by toxicity and limited potency. Here, we report on a novel permeation enhancer, Dimethyl palmitoyl ammonio propanesulfonate (PPS), with excellent enhancement potential and minimal toxicity. PPS was tested for dose- and time-dependent cytotoxicity, delivery of two model fluorescent molecules, sulforhodamine-B and FITC-insulin in vitro, and absorption enhancement of salmon calcitonin (sCT) in vivo. Caco-2 studies revealed that PPS is an effective enhancer of macromolecular transport while being minimally toxic. TEER measurements in Caco-2 monolayers confirmed the reversibility of the effect of PPS. Confocal microscopy studies revealed that molecules permeate via both paracellular and transcellular pathways in the presence of PPS. In vivo studies in rats showed that PPS enhanced relative bioavailability of sCT by 45-fold after intestinal administration. Histological studies showed that PPS does not induce damage to the intestine. PPS is an excellent permeation enhancer which provides new opportunities for developing efficacious oral/intestinal delivery systems for therapeutic macromolecules.
- Enzymatically in situ shell cross-linked micelles composed of 4-arm PPO-PEO and heparin for controlled dual drug delivery. [JOURNAL ARTICLE]
- J Control Release 2013 May 13.
We report a controlled dual drug delivery system using heparinized 4-arm poly(propylene oxide) (PPO)-poly(ethylene oxide) (PEO) micelles (cHTM) that are sterically stabilized by enzymatic shell cross-linking (SCL). Tyramine (TA) was chemically conjugated to 4-arm PPO-PEO (Tetronic) and heparin, resulting in Tetronic-TA (Tet-TA) and heparin-TA (Hep-TA), respectively. To prepare a series of cHTM, different amounts of Hep-TA were added to a micellar solution of Tet-TA, followed by addition of horseradish peroxidase (HRP) and hydrogen peroxide (H2O2) to trigger SCL between TA groups at the micellar surfaces. Increasing the feed amount of Hep-TA led to increased heparin content of cHTM, thereby resulting in increased micelle size with more negatively charged surfaces. All SCL micelles were found to be highly stable over 4weeks, showing negligible changes in their sizes and zeta potentials. Dual drug-loaded cHTM containing indomethacin (IMC) and basic fibroblast growth factor (bFGF) were prepared via a one-pot procedure. With favorable IMC loading, the loading efficiencies of bFGF into cHTM were much higher than those in the controls due to the presence of heparin on the micellar surface. After bFGF was added to IMC loaded cHTM the surface of HTM became less negative with an increase in size, suggesting successful binding of positively charged bFGF to heparinized micelle surfaces. In vitro release data clearly showed more sustained release of IMC and bFGF as compared with non-cross-linked micelles. Based on these results, we suggest that cHTM can be used as a new drug delivery platform for controlled dual drug release.
- Use of optical imaging to progress novel therapeutics to the clinic. [JOURNAL ARTICLE]
- J Control Release 2013 May 13.
There is an undisputed need for employment and improvement of robust technology for real-time analyses of therapeutic delivery and responses in clinical translation of gene and cell therapies. Over the past decade, optical imaging has become the in vivo imaging modality of choice for many preclinical laboratories due to its efficiency, practicality and affordability, while more recently, the clinical potential for this technology is becoming apparent. This review provides an update on the current state of the art in in vivo optical imaging and discusses this rapidly improving technology in the context of it representing a translation enabler or indeed a future clinical imaging modality in its own right.
- Cell surface clustering of heparan sulfate proteoglycans by amphipathic cell-penetrating peptides does not contribute to uptake. [JOURNAL ARTICLE]
- J Control Release 2013 May 10.
For arginine-rich cell-penetrating peptides (CPPs), an association with heparan sulfate (HS) chains is considered the first step in the stimulation of uptake for many cells. Much less is known about the role of HS chains in the cell-association and internalization of arginine-free amphipathic CPP such as transportan-10 (TP10). Here, we report that various TP10 analogs differ in their capacity to accumulate on HS-rich plasma membranes in an HS-dependent manner. No accumulation was observed on HS-poor plasma membranes or when HS was removed by enzymatic cleavage. The TP10 analog that strongly clustered on the cell surface, also showed a pronounced capacity to form clusters with HS chains in solution. However, aggregation occurred in a thermodynamically different way compared to the interaction of arginine-rich CPP with HS. To monitor the impact of the peptide on the aggregation of the glycocalyx by time-lapse microscopy, sialic acids were visualized by metabolic labeling using copper-free click chemistry to attach fluorophores to metabolically incorporated azido sugars. Strikingly, a highly enhanced HS-mediated accumulation on the plasma membrane of a particular TP10 analog did not correlate with a better uptake. These findings illustrate that the mode of interaction between cell-penetrating peptides and HS chains has important functional consequences regarding peptide internalization and that there is no direct coupling of interaction, accumulation and uptake.
- Biodegradable hybrid polymer micelles for combination drug therapy in ovarian cancer. [JOURNAL ARTICLE]
- J Control Release 2013 May 9.
The co-delivery of drug combination at a controlled ratio via the same vehicle to the cancer cells is offering the advantages such as spatial-temporal synchronization of drug exposure, synergistic therapeutic effects and increased therapeutic potency. In an attempt to develop such multidrug vehicle this work focuses on functional biodegradable and biocompatible polypeptide-based polymeric micelles. Triblock copolymers containing the blocks of ethylene glycol, glutamic acid and phenylalanine (PEG-PGlu-PPhe) were successfully synthesized via NCA-based ring-opening copolymerization and their composition was confirmed by (1)H NMR. Self-assembly behavior of PEG-PGlu90-PPhe25 was utilized for the synthesis of hybrid micelles with PPhe hydrophobic core, cross-linked ionic PGlu intermediate shell layer, and PEG corona. Cross-linked (cl) micelles were about 90nm in diameter (ξ-potential=-20mV), uniform (narrow size distribution), and exhibited nanogels-like behavior. Degradation of cl-micelles was observed in the presence of proteolytic enzymes (cathepsin B). The resulting cl-micelles can incorporate the combination of drugs with very different physical properties such as cisplatin (15 w/w% loading) and paclitaxel (9 w/w% loading). Binary drug combination in cl-micelles exhibited synergistic cytotoxicity against human ovarian A2780 cancer cells and exerted a superior antitumor activity by comparison to individual drug-loaded micelles or free cisplatin in cancer xenograft model in vivo. Tunable composition and stability of these hybrid biodegradable micelles provide platform for drug combination delivery in a broad range of cancers.