Synthesis and characterization of RGD-fatty acid amphiphilic micelles as targeted delivery carriers for anticancer agents

Preparation, stability and controlled release properties of starch-based micelles for oral delivery of hydrophobic bioactive molecules

Amphiphilic starches incorporating fatty acid ester chains of varying lengths and degrees of substitution (DS) were synthesized to fabricate starch-based micelles for oral delivery of hydrophobic bioactive molecules. The assembly of the amphiphilic starches is influenced by the concentration, temperature, and the chain length and DS of their fatty acid ester chain. Highly acidic environment can hydrolyze the amphiphilic starches, resulting in the formation of small-sized micelles. Conversely, high ionic concentration hinders the self-assembly of amphiphilic starches and the digestive fluids can dilute the amphiphilic starches concentration, leading to the micelle dissociation. However, amphiphilic starches with longer chain length and/or higher DS of the fatty acid ester chain possess greater hydrophobicity, enhancing the stability of starch-based micelles under varying conditions and favouring the protection of Trp-2 peptides during storage. The micelles demonstrate high cell bioaccessibility for Trp-2 peptides, with 59.25 % of Trp-2 peptides being transferred by the intestinal epithelium. These findings suggest a potential starch-based micelle system can be adjusted for the oral delivery of hydrophobic bioactive molecules.

A comparative study on micelles, liposomes and solid lipid nanoparticles for paclitaxel delivery

The purpose of this work was to compare the in vitro and in vivo characteristics of LDV-targeted lipid-based micelles, liposomes and solid lipid nanoparticles (SLN) to provide further insights into their therapeutic potential for clinical development. Micelles, liposomes and SLN were prepared using LDV peptide amphiphiles and palmitic acid-derived lipids using solvent evaporation, thin-film hydration and microfluidic mixing respectively. Nanocarriers were characterized for their physicochemical properties, paclitaxel loading efficiency, in vitro release behavior, stability in biological media as well as in vivo antitumor efficacy in melanoma xenograft model. TEM and DLS results confirmed the presence of paclitaxel-loaded nanosized micelles (6 to 12 nm), liposomes (123.31 ± 5.87 nm) and SLN (80.53 ± 5.37 nm). SLN demonstrated the slowest paclitaxel release rate and the highest stability in biological media compared to micelles and liposomes. Paclitaxel-loaded SLN demonstrated a statistically significant delay in tumor growth compared to mice treated with paclitaxel-loaded liposomes and paclitaxel-loaded micelles (p < 0.05). The results obtained in this study indicate the potential of SLN as drug delivery vehicles for anticancer therapy.

Nano-sized solid dispersions based on hydrophobic-hydrophilic conjugates for dissolution enhancement of poorly water-soluble drugs

The aim of this study was to investigate hydrophilic-hydrophobic conjugates as new carriers for nano-sized solid dispersions (SDs). The amphiphilic conjugates were prepared via an esterification reaction between hydroxypropyl methylcellulose (HPMC) and zein. Four formulations of conjugates were investigated with different ratios of zein to HPMC (1:5, 1:10, 1:20, and 1:40). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy and particle size analyses were performed to characterize and optimize the formulation for SD. Isradipine and prednisolone were chosen as poorly water-soluble drugs for SD using the conjugate as a carrier. Dissolution tests, particle size analyses, powder X-ray diffraction and FTIR were conducted to determine the dissolution enhancement and its mechanism. The conjugate formed small particles as a self-assembled carrier. Although the SD with isradipine or prednisolone showed a small increase in particle size, the dissolution rate of those drugs in SD increased significantly compared to pure drugs. The interaction between the drug and conjugate was attributed to the formation of small particles and changes to the drug crystallinity. This study demonstrated that the hydrophilic-hydrophobic conjugate is a promising material for SD, with the potential of reducing drug particles to nano size in addition to promoting drug amorphousness or molecular interactions.

Design of liposomal formulations for cell targeting

Liposomes have gained extensive attention as carriers for a wide range of drugs due to being both nontoxic and biodegradable as they are composed of substances naturally occurring in biological membranes. Active targeting for cells has explored specific modification of the liposome surface by functionalizing it with specific targeting ligands in order to increase accumulation and intracellular uptake into target cells. None of the Food and Drug Administration-licensed liposomes or lipid nanoparticles are coated with ligands or target moieties to delivery for homing drugs to target tissues, cells or subcellular organelles. Targeted therapies (with or without controlled drug release) are an emerging and relevant research area. Despite of the numerous liposomes reviews published in the last decades, this area is in constant development. Updates urgently needed to integrate new advances in targeted liposomes research. This review highlights the evolution of liposomes from passive to active targeting and challenges in the development of targeted liposomes for specific therapies.

In Vitro and In Vivo Efficacy of Self-Assembling RGD Peptide Amphiphiles for Targeted Delivery of Paclitaxel

PURPOSE

The objective of this work was to compare the efficacy of self-assembling cyclic and linear RGD peptide amphiphiles as carriers for delivering paclitaxel to αvβ3 integrin overexpressing tumors.

METHODS

Linear (C18-ADA5-RGD) and cyclic (C18-ADA5-cRGDfK) peptide amphiphiles were synthesized and characterized for CMC, aggregation number and micelle stability using fluorescence spectroscopy methods. Size and morphology of micelles was studied using TEM. Fluorescence polarization and confocal microscopy assays were established to compare binding and internalization of micelles. The targeting efficacy was studied in A2058 cells using cytotoxicity assay as well as in vivo in melanoma xenograft mouse model.

RESULTS

The linear and cyclic RGD amphiphiles exhibited CMC of 25 and 8 μM, respectively, formed nano-sized spherical micelles and showed competitive binding to αvβ3 integrin protein. FITC-loaded RGD micelles rapidly internalized into A2058 melanoma cells. Paclitaxel-loaded RGD micelles exhibited higher cytotoxicity compared with free drug in A2058 cells in vitro as well as in vivo.

CONCLUSION

Cyclic RGD micelles exhibited better targeting efficacy but were less effective compared to linear RGD micelles as drug delivery vehicle due to lower drug solubilization capacity and lesser kinetic stability. Results from the study proved the effectiveness of self-assembling low molecular weight RGD amphiphiles as carriers for targeted delivery of paclitaxel.

Fatty acid-RGD peptide amphiphile micelles as potential paclitaxel delivery carriers to α(v)β₃ integrin overexpressing tumors

PURPOSE

To design and synthesize fatty acid-RGD peptide amphiphiles with ADA linker for their potential delivery of hydrophobic drugs like paclitaxel targeted to α(v)β(3) integrin overexpressing tumors.

METHODS

Four amphiphiles - C16 or C18 fatty acid-RGD peptide and ADA linker were designed and synthesized. CMC, size and zeta potential of the amphiphiles were determined. FITC loaded micelles uptake into A2058 melanoma cells was investigated at 4°C and 37°C using confocal microscopy. Paclitaxel was loaded into micelles, their encapsulation efficiency and cytotoxicity of micelles was evaluated. The stability of the micelles was determined using FRET method.

RESULTS

Mass, (1)H NMR and HPLC analysis confirmed the formation of amphiphiles and their purity. Among the amphiphiles, C18-(ADA)(2)-RGD amphiphile exhibited lowest CMC (9.00 ± 1.73 μM) and its micelles had suitable size (194.63 ± 44.86 nm) and zeta potential (0.27 ± 1.96 mV) for targeting. The cellular uptake of the micelles was temperature dependent and the micelles were stable. The IC50 of paclitaxel loaded in micelles decreased 50% in α(v)β(3) integrin overexpressing cells and showed a 4 fold increase in normal cells when compared to free paclitaxel.

CONCLUSION

Amphiphiles of fatty acids-ADA-RGD were synthesized. These amphiphiles formed stable micelles and were effective as targeted delivery carriers to α(v)β(3) integrin overexpressing tumors.

Preparation and physicochemical characterization of a novel paclitaxel-loaded amphiphilic aminocalixarene nanoparticle platform for anticancer chemotherapy

OBJECTIVES

This paper describes the development and optimization of a nanoparticle delivery platform for the anticancer agent, paclitaxel, using a novel amphiphilic carrier, tetrahexyloxy-tetra-p-aminocalix[4]arene (A4C(6) ).

METHODS

Nanoparticles were successfully prepared at pH4 by an emulsion evaporation method whereby an organic phase containing paclitaxel: A4C(6) (molar ratio 1:10) was dispersed by probe sonication into an aqueous phase containing 0.5% w/v polyvinyl alcohol as stabilizer.

KEY FINDINGS

The drug-loaded nanoparticles had a mean size of 78.7±20.7nm, surface potential of 38.3±7.67mV, and paclitaxel loading and encapsulation efficiencies of 69.1±5.3µg drug/mg carrier and 50.4±3.2%, respectively. Transmission electron micrographs showed discrete particles with no evidence of agglomeration. In-vitro dissolution into phosphate buffered saline supplemented with 4% bovine serum albumin showed 32.7±3.9%, 82.6±5.3% and 91.0±6.0% of the encapsulated paclitaxel load was released at 5, 72 and 120h, respectively.

CONCLUSIONS

This is the first report on the use of amino-substituted amphiphilic calixarenes for the encapsulation of anticancer agents. The nanoparticles produced were significantly smaller than, but had comparable drug loads to the Abraxane nanoparticles, and have the potential to achieve targeted delivery of paclitaxel to tumour tissues.

Integrin targeted drug and gene delivery

IMPORTANCE OF THE FIELD

Recently, there has been substantial progress in the development of integrin targeted pharmaceuticals and drug delivery systems. Integrin is an important member in the cell adhesion molecule family, which is involved in regulation of complex biological conditions, from keeping normal physiological activities to causing cellular dysfunction in diseased cells. Hence, it is timely to summarize the recent developments in integrin targeted drug and gene delivery systems to understand better their advantages and limitations.

AREAS COVERED IN THIS REVIEW

In this review, advances in the discovery and clinical trials of these integrin antagonists against different integrin subunits are summarized and discussed. Besides using integrin inhibitor as a single therapeutic agent, integrin antagonists that were conjugated to cytotoxic drugs by synthetic chemistry or coupled to biomacromolecules by either DNA recombination technology or fusion protein technology for integrin targeted therapy have been explored. Furthermore, nanoparticles with integrin targeting ligands for both drug and gene delivery, typically for antiangiogenesis and anticancer therapy, are highlighted and evaluated.

WHAT THE READER WILL GAIN

This review sheds light on the future development of integrin targeted drug and/or gene delivery systems.

TAKE HOME MESSAGE

Although thus far there are still limitations, integrin targeted delivery systems have already shown their potential as important pharmaceuticals in the near future.

Angiotensin II receptor blocker and statins lower elevated levels of osteopontin in essential hypertension--results from the EUTOPIA trial

BACKGROUND

Osteopontin is a pleiotropic cytokine that has been implicated as a key factor in the development of atherosclerosis, a major complication of hypertension. We have earlier shown that olmesartan reduces mediators of vascular inflammation in patients with hypertension and cardiovascular disease. We aimed at studying the effect of olmesartan and/or pravastatin on osteopontin plasma levels, and the association between vascular inflammation markers and osteopontin in hypertensive patients.

METHODS

We assessed a panel of vascular inflammation markers and osteopontin during 12 weeks of therapy with 20mg olmesartan (n=94) or placebo (n=96) in a prospective, double-blind, multi-center study in patients with essential hypertension (re-evaluation of the EUTOPIA trial blood samples). Pravastatin (20mg) was added to the double-blind therapy at week 6 in both arms. The association of demographic variables and inflammation markers with osteopontin has been analyzed as well.

RESULTS

Baseline osteopontin plasma concentrations in the study population were elevated compared to healthy controls (32.85+/-19.04ng/mL vs. 23.82+/-3.69ng/mL, p=0.027). Mono-therapy with olmesartan and co-therapy with pravastatin reduced levels of circulating osteopontin (p<0.001). The addition of pravastatin to the placebo treatment-arm resulted in a reduction of osteopontin levels as well (p<0.01). osteopontin plasma levels correlated with VCAM-1 (r=0.27; p=0.0002), ICAM-1 (r=0.18; p=0.015), IL-6 (r=0.35; p<0.0001) and hsCRP (r=0.22; p=0.0022).

CONCLUSION

We show, for the first time, that olmesartan significantly decreases osteopontin concentrations. Co-therapy with pravastatin also reduces osteopontin levels. Elevated osteopontin levels in hypertensive patients correlate with adhesion molecules and inflammation markers.

Targeting the delivery of glycan-based paclitaxel prodrugs to cancer cells via glucose transporters

This report describes the synthesis of four novel paclitaxel based prodrugs with glycan conjugation (1-4). Glycans were conjugated using an ester or ether bond as the linker between 2'-paclitaxel and the 2'-glucose or glucuronic acid moiety. These prodrugs showed good water solubility and selective cytotoxicity against cancer cell lines, but showed reduced toxicity toward normal cell lines and cancer cell lines with low expression levels of GLUTs. The ester conjugated prodrug 1 showed the most cytotoxicity among the prodrugs examined and could be transported into cells via GLUTs. Fluorescent and confocal microscopy demonstrated that targeted cells exhibited morphological changes in tubulin and chromosomal alterations that were similar to those observed with paclitaxel treatment. Therefore, these glycan-based prodrugs may be good drug candidates for cancer therapy, and the glycan conjugation approach is an alternative method to enhance the targeted delivery of other drugs to cancer cells that overexpress GLUTs.

The role of osteopontin in the development of albuminuria

Several gene array studies have suggested that osteopontin (Opn) expression strongly correlates with albuminuria and glomerular disease. Urinary Opn concentration and kidney Opn immunoreactivity were found to be increased in patients with steroid-sensitive nephrotic syndrome. In addition, renal Opn mRNA was increased in the Ins2(Akita) mouse model of type 1 diabetic nephropathy, in the LPS-induced albuminuria model, and in glomeruli of puromycin aminonucleotide-induced nephrotic rats. Opn knockout mice did not develop albuminuria in response to LPS injection, and Opn knockout mice were protected from diabetes-induced albuminuria and mesangial expansion. In the glomerulus, Opn immunostaining was increased specifically in podocytes. Treatment of podocytes with recombinant Opn activated the NF-kappaB pathway, increased expression of urokinase plasminogen activator and matrix metalloproteinases 2 and 9, and increased podocyte motility. Taken together, these results indicate that Opn plays an important role in the development of albuminuria, possibly by modulating podocyte signaling and motility.

Viral infection and human disease--insights from minimotifs

Short functional peptide motifs cooperate in many molecular functions including protein interactions, protein trafficking, and posttranslational modifications. Viruses exploit these motifs as a principal mechanism for hijacking cells and many motifs are necessary for the viral life-cycle. A virus can accommodate many short motifs in its small genome size providing a plethora of ways for the virus to acquire host molecular machinery. Host enzymes that act on motifs such as kinases, proteases, and lipidation enzymes, as well as protein interaction domains, are commonly mutated in human disease, suggesting that the short peptide motif targets of these enzymes may also be mutated in disease; however, this is not observed. How can we explain why viruses have evolved to be so dependent on motifs, yet these motifs, in general do not seem to be as necessary for human viability? We propose that short motifs are used at the system level. This system architecture allows viruses to exploit a motif, whereas the viability of the host is not affected by mutation of a single motif.

Novel near-infrared fluorescent integrin-targeted DFO analogue

Desferrioxamine (DFO), a siderophore initially isolated from Streptomyces pilosus, possesses extraordinary metal binding properties with wide biomedical applications that include chelation therapy, nuclear imaging, and antiproliferation. In this work, we prepared a novel multifunctional agent consisting of (i) a near-infrared (NIR) fluorescent probe-cypate; (ii) an integrin alpha vbeta3 receptor (ABIR)-avid cyclic RGD peptide, and (iii) a DFO moiety, DFO-cypate-cyclo[RGDfK(approximately)] (1, with approximately representing the cypate conjugation site at the side chain of lysine; f is d-phenylalanine). Compound 1 and two control compounds, cypate-cyclo[RGDfK(approximately)] ( 2) and cypate-DFO ( 3), were synthesized by modular assembly of the corresponding protected RGD peptide cyclo[R(Pbf)GD(OBut)fK] and DFO on the dicarboxylic acid-containing cypate scaffold in solution. The three compounds exhibited similar UV-vis and emission spectral properties. Metal binding analysis shows that DFO as well as 1 and 3 exhibited relatively high binding affinity with Fe(III), Al(III), and Ga(III). In contrast to Ga(III), the binding of Fe to 1 and 3 quenched the fluorescence emission of cypate significantly, suggesting an efficient metal-mediated approach to perturb the spectral properties of NIR fluorescent carbocyanine probes. In vitro, 1 showed a high ABIR binding affinity (10 (-7) M) comparable to that of 2 and the reference peptide cyclo(RGDfV), indicating that both DFO and cypate motifs did not interfere significantly with the molecular recognition of the cyclic RGD motif with ABIR. Fluorescence microscopy showed that internalization of 1 and 2 in ABIR-positive A549 cells at 1 h postincubation was higher than 3 and cypate alone, demonstrating that incorporating ABIR-targeting RGD motif could improve cellular internalization of DFO analogues. The ensemble of these findings demonstrate the use of multifunctional NIR fluorescent ABIR-targeting DFO analogues to modulate the spectral properties of the NIR fluorescent probe by the chelating properties of DFO and visualize intracellular delivery of DFO by receptor-specific peptides. These features provide a strategy to explore the potential of 1 in tumor imaging and treatment as well as some molecular recognition processes mediated by metal ions.