Pharmacometrics and delivery of novel nanoformulated PEG-b-poly(epsilon-caprolactone) micelles of rapamycin

Anticancer potential of curcumin-cyclodextrin complexes and their pharmacokinetic properties

Cancer is one of the most common diseases throughout the world, with many treatment modalities currently being used, and new treatment strategies being sought. Most chemotherapeutic molecules have shown extensive toxicity for normal cells, which leads to severe adverse effects. Chemotherapy may also lead to drug resistance, which is one of the major obstacles to the clinical treatment of cancer. Curcumin, a polyphenolic natural compound, has long been considered a therapeutic molecule for a variety of diseases and possesses anti-cancer, anti-oxidant, and anti-inflammatory properties. However, its use is limited due to its hydrophobic nature, poor solubility in water at acidic or neutral pH, and limited bioavailability at the tumor site. Cyclodextrin complexes of curcumin increase curcumin's water solubility, as well as its physicochemical stability to hydrolysis and photochemical decomposition. The most common type of cyclodextrin used for pharmaceutical preparations is β-cyclodextrin. This review focuses on different curcumin-cyclodextrin formulations and compares their pharmacokinetic parameters and efficacy.

Optimization of Synthesis of Silver Nanoparticles Conjugated with Lepechinia meyenii (Salvia) Using Plackett-Burman Design and Response Surface Methodology—Preliminary Antibacterial Activity

In the present investigation, an ethanolic fraction (EF) of Lepechinia meyenii (salvia) was prepared and fractionated by gradient column chromatography, and the main secondary metabolites present in the EF were identified by HPLC-MS. Silver nanoparticles (AgNPs) were synthesized and conjugated with the EF of Lepechinia meyenii (salvia). The AgNPs synthesis was optimized using Plackett-Burman design and response surface methodology (RSM), considering the following independent variables: stirring speed, synthesis pH, synthesis time, synthesis temperature and EF volume. The AgNPs synthesized under the optimized conditions were characterized by UV visible spectroscopy (UV-VIS), Fourier Transform Infrared Spectroscopy (FT-IR), Dynamic Light Scattering (DLS) and Scanning Transmission Electron Microscopy (STEM). The antibacterial activity of the AgNPs against Staphylococcus aureus (ATCC® 25923) was evaluated. The following flavonoids were identified: rosmarinic acid, diosmin and hesperetin-7-O-rutinoside. The optimized conditions for the synthesis of nanoparticles were pH 9.45, temperature 49.8 °C, volume of ethanolic fraction 152.6 µL and a reaction time of 213.2 min. The obtained AgNPs exhibited an average size of 43.71 nm and a resonance plasmon of 410–420 nm. Using FT-IR spectroscopy, the disappearance of the peaks between 626.50 and 1379.54 cm−1 was evident with the AgNPs, which would indicate the participation of these functional groups in the synthesis and protection of the nanoparticles. A hydrodynamic size of 47.6 nm was obtained by DLS, while a size of 40–60 nm was determined by STEM. The synthesized AgNPs conjugated with the EF showed a higher antibacterial activity than the EF alone. These results demonstrate that the AgNPs synthesized under optimized conditions conjugated with the EF of the Lepechinia meyenii (salvia) presented an increased antibacterial activity.

Green Synthesis of a Novel Silver Nanoparticle Conjugated with Thelypteris glandulosolanosa (Raqui-Raqui): Preliminary Characterization and Anticancer Activity

In the last decade, the green synthesis of nanoparticles has had a prominent role in scientific research for industrial and biomedical applications. In this current study, silver nitrate (AgNO3) was reduced and stabilized with an aqueous extract of Thelypteris glandulosolanosa (Raqui-raqui), forming silver nanoparticles (AgNPs-RR). UV-vis spectrophotometry, dynamic light scattering (DLS), and scanning transmission electron microscopy (STEM) were utilized to analyze the structures of AgNPs-RR. The results from this analysis showed a characteristic peak at 420 nm and a mean hydrodynamic size equal to 39.16 nm, while the STEM revealed a size distribution of 6.64–51.00 nm with an average diameter of 31.45 nm. Cellular cytotoxicity assays using MCF-7 (ATCC® HTB-22™, mammary gland breast), A549 (ATCC® CCL-185, lung epithelial carcinoma), and L929 (ATCC® CCL-1, subcutaneous connective tissue of Mus musculus) demonstrated over 42.70% of MCF-7, 59.24% of A549, and 8.80% of L929 cells had cell death after 48 h showing that this nanoparticle is more selective to disrupt neoplastic than non-cancerous cells and may be further developed into an effective strategy for breast and lung cancer treatment. These results demonstrate that the nanoparticle surfaces developed are complex, have lower contact angles, and have excellent scratch and wear resistance.

Physical and Mechanical Characterization of a Functionalized Cotton Fabric with Nanocomposite Based on Silver Nanoparticles and Carboxymethyl Chitosan Using Green Chemistry

Cotton is the most widely used natural fiber for textiles but its innate capacity to absorb moisture, retain oxygen, and high specific surface area make it more prone to microbial contamination, becoming an appropriate medium for the growth of bacteria and fungi. In recent years, the incorporation of silver nanoparticles in textile products has been widely used due to their broad-spectrum antibacterial activity and low toxicity towards mammalian cells. The aim of the current study is to synthesize and characterize a nanocomposite based on silver nanoparticles and carboxymethyl chitosan (AgNPs-CMC), which was utilized to provide a functional finish to cotton fabric. The scanning electron microscope (SEM) to produce a scanning transmission electron microscope (STEM) image showed that the nanocomposite presents AgNPs with a 5–20 nm size. The X-ray diffraction (XRD) analysis confirmed the presence of silver nanoparticles. The concentration of silver in the functionalized fabric was evaluated by inductively coupled plasma optical emission spectrometry (ICP-OES), which reported an average concentration of 13.5 mg of silver per kg of functionalized fabric. SEM showed that silver nanoparticles present a uniform distribution on the surface of the functionalized cotton fabric fibers. On the other hand, by infrared spectroscopy, it was observed that the functionalized fabric variation (compared to control) had a displaced peak of intensity at 1594.32 cm−1, corresponding to carboxylate anions. Similarly, Raman spectroscopy showed an intense peak at 1592.84 cm−1, which corresponds to the primary amino group of carboxymethyl chitosan, and a peak at 1371.5 cm−1 corresponding to the carboxylic anions. Finally, the physical and mechanical tests of tensile strength and color index of the functional fabric reported that it was no different (p ˃ 0.05) than the control fabric. Our results demonstrate that we have obtained an improved functionalized cotton fabric using green chemistry that does not alter intrinsic properties of the fabric and has the potential to be utilized in the manufacturing of hospital garments.

Transferrin decorated-nanostructured lipid carriers (NLCs) are a promising delivery system for rapamycin in Alzheimer's disease: An in vivo study

Alzheimer's disease (AD), the most common neurodegenerative disorder, is characterized by progressive cognitive impairment and memory loss. The mammalian target of rapamycin (mTOR) signaling pathway could regulate learning and memory. The effect of rapamycin (Rapa) on mTOR activity could slow or prevent the progression of AD by affecting various essential cellular processes. Previously, we prepared transferrin (Tf) decorated-nanostructured lipid carriers (NLCs) for rapamycin (150 ± 9 nm) to protect the drug from chemical and enzymatic degradation and for brain targeted delivery of rapamycin. Herein, the effect of Tf-NLCs compared to untargeted anionic-NLCs and free rapamycin, were studied in amyloid beta (Aβ) induced rat model of AD. Behavioral test revealed that the Rapa Tf-NLCs were able to significantly improve the impaired spatial memory induced by Aβ. Histopathological studies of hippocampus also showed neural survival in Rapa Tf-NLCs treated group. The immunosuppressive, and delayed wound healing adverse effects in the rapamycin solution treated group were abolished by incorporating the drug into NLCs. The Aβ induced oxidative stress was also reduced by Rapa Tf-NLCs. Molecular studies on the level of Aβ, autophagy (LC3) and apoptotic (caspase-3) markers, and mTOR activity revealed that the Rapa Tf-NLCs decreased the Aβ level and suppressed the toxic effects of Aβ plaques by modulating the mTOR activity and autophagy, and decreasing the apoptosis level. As a conclusion, the designed Tf-NLCs could be an appropriate and a safe brain delivery system for rapamycin and make this drug more efficient in AD for improving memory and neuroprotection.

Antibacterial and Antifungal Activity of Functionalized Cotton Fabric with Nanocomposite Based on Silver Nanoparticles and Carboxymethyl Chitosan

Cotton is the most widely used natural fiber for textiles; however, the capacity of cotton fibers to absorb large amounts of moisture, retain oxygen, and have a high specific surface area makes them more prone to microbial contamination, becoming an appropriate medium for the growth of bacteria and fungi. In recent years, the incorporation of silver nanoparticles in textile products has been widely used due to their broad-spectrum antibacterial activity and low toxicity towards mammalian cells. The aim of the current study is to continue the assessment of our developed nanocomposite and evaluate the antibacterial and antifungal activity of the nanocomposite based on silver nanoparticles and carboxymethyl chitosan (AgNPs-CMC) against Escherichia coli, Staphylococcus aureus, and Candida albicans, evaluated by the well diffusion method. The antibacterial activity against E. coli and S. aureus was also evaluated by the qualitative method of inhibition zone and the quantitative method of colony counting. Likewise, the antifungal activity of the functionalized fabric against Candida albicans and Aspergillus niger was determined by the inhibition zone method and the antifungal activity method GBT 24346-2009, respectively. The functionalized fabric showed 100% antibacterial activity against E. coli and S. aureus and good antifungal activity against C. albicans and A. niger. Our results indicate that the functionalized fabric could be used in garments for hospital use to reduce nosocomial infections.

Safety Profile of Rapamycin Perfluorocarbon Nanoparticles for Preventing Cisplatin-Induced Kidney Injury

Cancer treatment-induced toxicities may restrict maximal effective dosing for treatment and cancer survivors' quality of life. It is critical to develop novel strategies that mitigate treatment-induced toxicity without affecting the efficacy of anti-cancer therapies. Rapamycin is a macrolide with anti-cancer properties, but its clinical application has been hindered, partly by unfavorable bioavailability, pharmacokinetics, and side effects. As a result, significant efforts have been undertaken to develop a variety of nano-delivery systems for the effective and safe administration of rapamycin. While the efficacy of nanostructures carrying rapamycin has been studied intensively, the pharmacokinetics, biodistribution, and safety remain to be investigated. In this study, we demonstrate the potential for rapamycin perfluorocarbon (PFC) nanoparticles to mitigate cisplatin-induced acute kidney injury with a single preventative dose. Evaluations of pharmacokinetics and biodistribution suggest that the PFC nanoparticle delivery system improves rapamycin pharmacokinetics. The safety of rapamycin PFC nanoparticles was shown both in vitro and in vivo. After a single dose, no disturbance was observed in blood tests or cardiac functional evaluations. Repeated dosing of rapamycin PFC nanoparticles did not affect overall spleen T cell proliferation and responses to stimulation, although it significantly decreased the number of Foxp3+CD4+ T cells and NK1.1+ cells were observed.

Brain targeted delivery of rapamycin using transferrin decorated nanostructured lipid carriers

Introduction: Recent studies showed that rapamycin, as a mammalian target of rapamycin (mTOR) inhibitor, could have beneficial therapeutic effects for the central nervous system (CNS) related diseases. However, the immunosuppressive effect of rapamycin as an adverse effect, the low water solubility, and the rapid in vivo degradation along with the blood-brain barrier-related challenges restricted the clinical use of this drug for brain diseases. To overcome these drawbacks, a transferrin (Tf) decorated nanostructured lipid carrier (NLC) containing rapamycin was designed and developed. Methods: Rapamycin-loaded cationic and bare NLCs were prepared using solvent diffusion and sonication method and well characterized. The optimum cationic NLCs were physically decorated with Tf. For in vitro study, the MTT assay and intracellular uptake of nanoparticles on U-87 MG glioblastoma cells were assessed. The animal biodistribution of nanoparticles was evaluated by fluorescent optical imaging. Finally, the in vivo effect of NLCs on the immune system was also studied. Results: Spherical NLCs with small particle sizes ranging from 120 to 150 nm and high entrapment efficiency of more than 90%, showed ≥80% cell viability. More importantly, Tf-decorated NLCs in comparison with bare NLCs, showed a significantly higher cellular uptake (97% vs 60%) after 2 hours incubation and further an appropriate brain accumulation with lower uptake in untargeted tissue in mice. Surprisingly, rapamycin-loaded NLCs exhibited no immunosuppressive effect. Conclusion: Our findings proposed that the designed Tf-decorated NLCs could be considered as a safe and efficient carrier for targeted brain delivery of rapamycin which may have an important value in the clinic for the treatment of neurological disorders.

Distinct effects of calcineurin dependent and independent immunosuppressants on endotoxaemia-induced nephrotoxicity in rats: Role of androgens

Evidence suggests that immunosuppressant therapies protect against harmful effects of endotoxaemia. In this study, we tested whether calcineurin-dependent (cyclosporine/tacrolimus) and -independent (sirolimus) immunosuppressants variably influence nephrotoxicity induced by endotoxaemia and whether this interaction is modulated by testosterone. We investigated the effects of immunosuppressants on renal histopathological, biochemical and inflammatory profiles in endotoxic male rats and the role of androgenic state in the interaction. Six-hour treatment of rats with lipopolysaccharide (LPS, 3 mg/kg) increased (i) serum urea/creatinine, (ii) width of proximal/distal tubules, (iii) tubular degeneration and vacuolation, (iv) Western protein expressions of renal toll-like receptor 4, monocyte chemoattractant protein-1, and NADPH oxidase-2, and (v) serum tumour necrosis factor-α and myeloperoxidase. These endotoxic manifestations were intensified and eliminated upon concurrent exposure to cyclosporine and sirolimus, respectively. The cyclosporine actions appear to be a class rather than a drug effect because similar exacerbation of LPS nephrotoxicity was observed in rats treated with tacrolimus, another calcineurin inhibitor (CNI). Moreover, the deteriorated renal outcomes in LPS/tacrolimus-treated rats were reduced after castration or androgen receptor blockade by flutamide. The data suggest opposite effects for calcineurin-dependent (exaggeration) and -independent immunosuppressants (amelioration) on renal defects of endotoxaemia and implicate androgenic pathways in the worsened endotoxic renal profile induced by CNIs.

Multifunctional polymeric micellar nanomedicine in the diagnosis and treatment of cancer

Polymeric micelles are a prevalent topic of research for the past decade, especially concerning their fitting ability to deliver drug and diagnostic agents. This delivery system offers outstanding advantages, such as biocompatibility, high loading efficiency, water-solubility, and good stability in biological fluids, to name a few. The multifunctional polymeric micellar architect offers the added capability to adapt its surface to meet the looked-for clinical needs. This review cross-talks the recent reports, proof-of-concept studies, patents, and clinical trials that utilize polymeric micellar family architectures concerning cancer targeted delivery of anticancer drugs, gene therapeutics, and diagnostic agents. The manuscript also expounds on the underlying opportunities, allied challenges, and ways to resolve their bench-to-bedside translation for allied clinical applications.

Nanodrug Delivery Systems for the Treatment of Ovarian Cancer

Despite advances achieved in medicine, chemotherapeutics still has detrimental side effects with ovarian cancer (OC), accounting for numerous deaths among females. The provision of safe, early detection and active treatment of OC remains a challenge, in spite of improvements in new antineoplastic discovery. Nanosystems have shown remarkable progress with impact in diagnosis and chemotherapy of various cancers, due to their ideal size; improved drug encapsulation within its interior core; potential to minimize drug degradation; improve in vivo drug release kinetics; and prolong blood circulation times. However, nanodrug delivery systems have few limitations regarding its accuracy of tumour targeting and the ability to provide sustained drug release. Hence, a cogent and strategic approach has focused on nanosystem functionalization with antibody-based ligands to selectively enhance cellular uptake of antineoplastics. Antibody functionalized nanosystems are (advanced) synthetic candidates, with a broad range of efficiency in specific tumour targeting, whilst leaving normal cells unaffected. This article comprehensively reviews the present status of nanosystems, with particular emphasis on nanomicelles for molecular diagnosis and treatment of OC. In addition, biomarkers of nanosystems provide important prospects as chemotherapeutic strategies to upsurge the survival rate of patients with OC.

Berunda Polypeptides: Biheaded Rapamycin Carriers for Subcutaneous Treatment of Autoimmune Dry Eye Disease

The USFDA-approved immunosuppressive drug rapamycin (Rapa), despite its potency, is limited by poor bioavailability and a narrow therapeutic index. In this study, we sought to improve bioavailability of Rapa with subcutaneous (SC) administration and to test its therapeutic feasibility and practicality in a murine model of Sjögren's syndrome (SS), a systemic autoimmune disease with no approved therapies. To improve its therapeutic index, we formulated Rapa with a carrier termed FAF, a fusion of the human cytosolic FK506-binding protein 12 (FKBP12) and an elastin-like polypeptide (ELP). The resulting 97 kDa FAF (i) has minimal burst release, (ii) is "humanized", (iii) is biodegradable, (iv) solubilizes two Rapa per FAF, and (v) avoids organic solvents or amphiphilic carriers. Demonstrating high stability, FAF remained soluble and monodisperse with a hydrodynamic radius of 8 nm at physiological temperature. A complete pharmacokinetic (PK) analysis of FAF revealed that the bioavailability of SC FAF was 60%, with significantly higher blood concentration during the elimination phase compared to IV FAF. The plasma concentration of Rapa delivered by FAF was 8-fold higher with a significantly increased plasma-to-whole blood ratio relative to free Rapa, 24 h after injection. To evaluate therapeutic effects, FAF-Rapa was administered SC every other day for 2 weeks to male non-obese diabetic (NOD) mice, which develop an SS-like autoimmune-mediated lacrimal gland (LG) inflammation and other characteristic features of SS. Both FAF-Rapa and free Rapa exhibited immunomodulatory effects by significantly suppressing lymphocytic infiltration, gene expression of IFN-γ, MHC II, type I collagen and IL-12a, and cathepsin S (CTSS) activity in LG compared to controls. Serum chemistry and histopathological analyses in major organs revealed no apparent toxicity of FAF-Rapa. Given its improved PK and equipotent therapeutic efficacy compared to free Rapa, FAF-Rapa is of further interest for systemic treatments for autoimmune diseases like SS.

Oligo(Lactic Acid)8-Rapamycin Prodrug-Loaded Poly(Ethylene Glycol)-block-Poly(Lactic Acid) Micelles for Injection

PURPOSE

To prepare an oligo(lactic acid)₈-rapamycin prodrug (o(LA)₈-RAP)-loaded poly(ethylene glycol)-block-poly(lactic acid) (PEG-b-PLA) micelle for injection and characterize its compatibility and performance versus a RAP-loaded PEG-b-PLA micelle for injection in vitro and in vivo.

METHODS

Monodisperse o(LA)₈ was coupled on RAP at the C-40 via DCC/DMAP chemistry, and conversion of o(LA)₈-RAP prodrug into RAP was characterized in vitro. Physicochemical properties of o(LA)₈-RAP- and RAP-loaded PEG-b-PLA micelles and their antitumor efficacies in a syngeneic 4 T1 breast tumor model were compared.

RESULTS

Synthesis of o(LA)₈-RAP prodrug was confirmed by ¹H NMR and mass spectroscopy. The o(LA)₈-RAP prodrug underwent conversion in PBS and rat plasma by backbiting and esterase-mediated cleavage, respectively. O(LA)₈-RAP-loaded PEG-b-PLA micelles increased water solubility of RAP equivalent to 3.3 mg/ml with no signs of precipitation. Further, o(LA)₈-RAP was released more slowly than RAP from PEG-b-PLA micelles. With added physical stability, o(LA)₈-RAP-loaded PEG-b-PLA micelles significantly inhibited tumor growth relative to RAP-loaded PEG-b-PLA micelles in 4 T1 breast tumor-bearing mice without signs of acute toxicity.

CONCLUSIONS

An o(LA)₈-RAP-loaded PEG-b-PLA micelle for injection is more stable than a RAP-loaded PEG-b-PLA micelle for injection, and o(LA)₈-RAP converts into RAP rapidly in rat plasma (t_1/2 = 1 h), resulting in antitumor efficacy in a syngeneic 4 T1 breast tumor model.

Multifunctional Platinum@BSA-Rapamycin Nanocarriers for the Combinatorial Therapy of Cerebral Cavernous Malformation

Platinum nanoparticles (PtNPs) are antioxidant enzyme-mimetic nanomaterials with significant potential for the treatment of complex diseases related to oxidative stress. Among such diseases, Cerebral Cavernous Malformation (CCM) is a major cerebrovascular disorder of genetic origin, which affects at least 0.5% of the general population. Accumulated evidence indicates that loss-of-function mutations of the three known CCM genes predispose endothelial cells to oxidative stress-mediated dysfunctions by affecting distinct redox-sensitive signaling pathways and mechanisms, including pro-oxidant and antioxidant pathways and autophagy. A multitargeted combinatorial therapy might thereby represent a promising strategy for the effective treatment of this disease. Herein, we developed a multifunctional nanocarrier by combining the radical scavenging activity of PtNPs with the autophagy-stimulating activity of rapamycin (Rapa). Our results show that the combinatorial targeting of redox signaling and autophagy dysfunctions is effective in rescuing major molecular and cellular hallmarks of CCM disease, suggesting its potential for the treatment of this and other oxidative stress-related diseases.

Central action of rapamycin on early ischemic injury and related cardiac depression following experimental subarachnoid hemorrhage

Early brain injury and related cardiac consequences play a key role in the devastating outcomes after subarachnoid hemorrhage (SAH). We reported that rapamycin exerts neuroprotection against cortical hypoxia early after SAH, but its mechanism is poorly understood. This in vivo study aimed to determine the potential role of the transcription factor STAT3 in the rapamycin-mediated neuroprotection in a mouse model of SAH. Forty C57BL/6 N mice were treated with an intracerebroventricular injection of rapamycin or vehicle (control) given after SAH induction by a filament perforation method, with or without STAT3 (Stattic) or ERK (PD98059) inhibitor pretreatment. Cerebral blood flow signals (%vascularity), brain tissue oxygen saturation (SbtO₂), and cardiac output (CO) were analyzed using an ultrasound/photoacoustic imaging system. Clinically relevant neurocardiac depression was notable in severe SAH mice. Rapamycin improved %vascularity, SbtO₂, and CO on day 1 after SAH onset. The beneficial effects of rapamycin on cerebral blood flow and oxygenation persisted until day 3, resulting in a significant reduction in post-SAH new cerebral infarctions and survival, as well as improved neurological functions, compared to the control group. All of the effects were attenuated by pretreatment with Stattic or PD98059. These data suggest that ERK and JAK/STAT3 pathways play an important role in the neurocardiac protection by rapamycin after SAH. We propose that rapamycin is a novel pharmacological strategy to target STAT3 activation, with a possible crosstalk through the ERK pathway, for the treatment of post-SAH early brain injury.

Organ preservation with targeted rapamycin nanoparticles: a pre-treatment strategy preventing chronic rejection in vivo

Hypothermic preservation is the standard of care for storing organs prior to transplantation. Endothelial and epithelial injury associated with hypothermic storage causes downstream graft injury and, as such, the choice of an ideal donor organ preservation solution remains controversial. Cold storage solutions, by design, minimize cellular necrosis and optimize cellular osmotic potential, but do little to assuage immunological cell activation or immune cell priming post transplantation. Thus, here we explore the efficacy of our previously described novel Targeted Rapamycin Micelles (TRaM) as an additive to standard-of-care University of Wisconsin preservation solution as a means to alter the immunological microenvironment post transplantation using in vivo models of tracheal and aortic allograft transplantation. In all models of transplantation, grafts pre-treated with 100 ng mL^-1 of TRaM augmented preservation solution ex vivo showed a significant inhibition of chronic rejection post-transplantation, as compared to UW augmented with free rapamycin at a ten-fold higher dose. Here, for the first time, we present a novel method of organ pretreatment using a nanotherapeutic-based cellular targeted delivery system that enables donor administration of rapamycin, at a ten-fold decreased dose during cold storage. Clinically, these pretreatment strategies may positively impact post-transplant outcomes and can be readily translated to clinical scenarios.

Nanoparticles Effectively Target Rapamycin Delivery to Sites of Experimental Aortic Aneurysm in Rats

Several drugs targeting the pathogenesis of aortic aneurysm have shown efficacy in model systems but not in clinical trials, potentially owing to the lack of targeted drug delivery. Here, we designed a novel drug delivery system using nanoparticles to target the disrupted aortic aneurysm micro-structure. We generated poly(ethylene glycol)-shelled nanoparticles incorporating rapamycin that exhibited uniform diameter and long-term stability. When injected intravenously into a rat model in which abdominal aortic aneurysm (AAA) had been induced by infusing elastase, labeled rapamycin nanoparticles specifically accumulated in the AAA. Microscopic analysis revealed that rapamycin nanoparticles were mainly distributed in the media and adventitia where the wall structures were damaged. Co-localization of rapamycin nanoparticles with macrophages was also noted. Rapamycin nanoparticles injected during the process of AAA formation evinced significant suppression of AAA formation and mural inflammation at 7 days after elastase infusion, as compared with rapamycin treatment alone. Correspondingly, the activities of matrix metalloproteinases and the expression of inflammatory cytokines were significantly suppressed by rapamycin nanoparticle treatment. Our findings suggest that the nanoparticle-based delivery system achieves specific delivery of rapamycin to the rat AAA and might contribute to establishing a drug therapy approach targeting aortic aneurysm.

Recent advances in polymeric micelles for anti-cancer drug delivery

Block co-polymeric micelles receive increased attention due to their ability to load therapeutics, deliver the cargo to the site of action, improve the pharmacokinetic of the loaded drug and reduce off-target cytotoxicity. While polymeric micelles can be developed with improved drug loading capabilities by modulating hydrophobicity and hydrophilicity of the micelle forming block co-polymers, they can also be successfully cancer targeted by surface modifying with tumor-homing ligands. However, maintenance of the integrity of the self-assembled system in the circulation and disassembly for drug release at the site of drug action remain a challenge. Therefore, stimuli-responsive polymeric micelles for on demand drug delivery with minimal off-target effect has been developed and extensively investigated to assess their sensitivity. This review focuses on discussing various polymeric micelles currently utilized for the delivery of chemotherapeutic drugs. Designs of various stimuli-sensitive micelles that are able to control drug release in response to specific stimuli, either endogenous or exogenous have been delineated.

Nanomicellar TGX221 blocks xenograft tumor growth of prostate cancer in nude mice

BACKGROUND

Combination of androgen ablation along with early detection and surgery has made prostate cancer highly treatable at the initial stage. However, this cancer remains the second leading cause of cancer death among American men due to castration-resistant progression, suggesting that novel therapeutic agents are urgently needed for this life-threatening condition. Phosphatidylinositol 3-kinase p110β is a major cellular signaling molecule and has been identified as a critical factor in prostate cancer progression. In a recent report, we established a nanomicelle-based strategy to deliver p110β-specific inhibitor TGX221 to prostate cancer cells by conjugating the surface of nanomicelles with a RNA aptamer against prostate specific membrane antigen (PSMA) present in all clinical prostate cancers. In this study, we tested this nanomicellar TGX221 for its in vivo anti-tumor effect in mouse xenograft models.

METHODS

Prostate cancer cell lines LAPC-4, LNCaP, C4-2 and 22RV1 were used to establish subcutaneous xenograft tumors in nude mice. Paraffin sections from xenograft tumor specimens were used in immunohistochemistry assays to detect AKT phosphorylation, cell proliferation marker Ki67 and proliferating cell nuclear antigen (PCNA), as well as 5-bromo-2-deoxyuridine (BrdU) incorporation. Quantitative PCR assay was conducted to determine prostate-specific antigen (PSA) gene expression in xenograft tumors.

RESULTS

Although systemic delivery of unconjugated TGX221 significantly reduced xenograft tumor growth in nude mice compared to solvent control, the nanomicellar TGX221 conjugates completely blocked tumor growth of xenografts derived from multiple prostate cancer cell lines. Further analyses revealed that AKT phosphorylation and cell proliferation indexes were dramatically reduced in xenograft tumors received nanomicellar TGX221 compared to xenograft tumors received unconjugated TGX221 treatment. There was no noticeable side effect by gross observation or at microscopic level of organ tissue section.

CONCLUSION

These data strongly suggest that prostate cancer cell-targeted nanomicellar TGX221 is an effective anti-cancer agent for prostate cancer.

Immunosuppressive and anti-inflammatory properties of engineered nanomaterials

Nanoparticle interactions with various components of the immune system are determined by their physicochemical properties such as size, charge, hydrophobicity and shape. Nanoparticles can be engineered to either specifically target the immune system or to avoid immune recognition. Nevertheless, identifying their unintended impacts on the immune system and understanding the mechanisms of such accidental effects are essential for establishing a nanoparticle's safety profile. While immunostimulatory properties have been reviewed before, little attention in the literature has been given to immunosuppressive and anti-inflammatory properties. The purpose of this review is to fill this gap. We will discuss intended immunosuppression achieved by either nanoparticle engineering, or the use of nanoparticles to carry immunosuppressive or anti-inflammatory drugs. We will also review unintended immunosuppressive properties of nanoparticles per se and consider how such properties could be either beneficial or adverse.

Characterization and pharmacokinetic analysis of crystalline versus amorphous rapamycin dry powder via pulmonary administration in rats

The pharmacokinetics of inhaled rapamycin (RAPA) is compared for amorphous versus crystalline dry powder formulations. The amorphous formulation of RAPA and lactose (RapaLac) was prepared by thin film freezing (TFF) using lactose as the stabilizing agent in the weight ratio 1:1. The crystalline formulation was prepared by wet ball milling RAPA and lactose and posteriorly blending the mixture with coarse lactose (micronized RAPA/micronized lactose/coarse lactose=0.5:0.5:19). While both powders presented good aerosolization performance for lung delivery, TFF formulation exhibited better in vitro aerodynamic properties than the crystalline physical mixture. Single-dose 24h pharmacokinetic studies were conducted in Sprague-Dawley rats following inhalation of the aerosol mist in a nose-only inhalation exposure system. Lung deposition was higher for the crystalline group than for the TFF group. Despite higher pulmonary levels of drug that were found for the crystalline group, the systemic circulation (AUC₀₋₂₄) was higher for the amorphous group (8.6 ngh/mL) than for crystalline group (2.4 ngh/mL) based on a five-compartmental analysis. Lung level profiles suggest that TTF powder stays in the lung for the same period of time as the crystalline powder but it presented higher in vivo systemic bioavailability due to its enhanced solubility, faster dissolution rate and increased FPF at a more distal part of the lungs.

Single rapamycin administration induces prolonged downward shift in defended body weight in rats

Manipulation of body weight set point may be an effective weight loss and maintenance strategy as the homeostatic mechanism governing energy balance remains intact even in obese conditions and counters the effort to lose weight. However, how the set point is determined is not well understood. We show that a single injection of rapamycin (RAP), an mTOR inhibitor, is sufficient to shift the set point in rats. Intraperitoneal RAP decreased food intake and daily weight gain for several days, but surprisingly, there was also a long-term reduction in body weight which lasted at least 10 weeks without additional RAP injection. These effects were not due to malaise or glucose intolerance. Two RAP administrations with a two-week interval had additive effects on body weight without desensitization and significantly reduced the white adipose tissue weight. When challenged with food deprivation, vehicle and RAP-treated rats responded with rebound hyperphagia, suggesting that RAP was not inhibiting compensatory responses to weight loss. Instead, RAP animals defended a lower body weight achieved after RAP treatment. Decreased food intake and body weight were also seen with intracerebroventricular injection of RAP, indicating that the RAP effect is at least partially mediated by the brain. In summary, we found a novel effect of RAP that maintains lower body weight by shifting the set point long-term. Thus, RAP and related compounds may be unique tools to investigate the mechanisms by which the defended level of body weight is determined; such compounds may also be used to complement weight loss strategy.

CD44-tropic polymeric nanocarrier for breast cancer targeted rapamycin chemotherapy

In contrast with the conventional targeting of nanoparticles to cancer cells with antibody or peptide conjugates, a hyaluronic acid (HA) matrix nanoparticle with intrinsic-CD44-tropism was developed to deliver rapamycin for localized CD44-positive breast cancer treatment. Rapamycin was chemically conjugated to the particle surface via a novel sustained-release linker, 3-amino-4-methoxy-benzoic acid. The release of the drug from the HA nanoparticle was improved by 42-fold compared to HA-temsirolimus in buffered saline. In CD44-positive MDA-MB-468 cells, using HA as drug delivery carrier, the cell viability was significantly decreased compared to free rapamycin and CD44-blocked controls. Rat pharmacokinetics showed that the area under the curve of HA nanoparticle formulation was 2.96-fold greater than that of the free drug, and the concomitant total body clearance was 8.82-fold slower. Moreover, in immunocompetent BALB/c mice bearing CD44-positive 4T1.2neu breast cancer, the rapamycin-loaded HA particles significantly improved animal survival, suppressed tumor growth and reduced the prevalence of lung metastasis.

FROM THE CLINICAL EDITOR

This study demonstrates increased efficiency of rapamycin delivery and consequential treatment effects in a breast cancer model by hyaluronic acid - L-rapamycin conjugates with intrinsic tropism for CD44-positive cells.

Cholesterol-poly(ethylene) glycol nanocarriers for the transscleral delivery of sirolimus

The aim of this study was to prepare and characterize cholesterol-poly(ethylene) glycol (chol-PEG) nanocarriers of two different molecular weights (1 and 5 kDa) and to determine their effect on the transscleral retention and permeation of a lipophilic multi-therapeutic agent, sirolimus (rapamycin), with potential application in angiogenic and immunogenic ocular diseases. Sirolimus-containing nanocarriers were prepared using the thin-film hydration method and characterized for their physicochemical properties including size, drug entrapment (EE) and loading (DL) efficiencies, stability, surface charge, morphology, critical micelle concentration (CMC) and thermal properties. Ussing chambers were used to determine the retention and permeability of sirolimus-containing nanocarriers in porcine sclera followed by ultrastructural tissue examination. Sirolimus-containing nanocarriers had an average size of 11.7 nm (chol-PEG 1 kDa) and 13.8 nm (chol-PEG 5 kDa) and zeta potentials of 0.41 and -1.05, respectively. Both nanocarriers had similar transscleral permeabilities (chol-PEG 1 kDa 6.44 × 10(-7) and 5 kDa 6.16 × 10(-7) cm2 s(-1)), and very high scleral retention compared with a free solution of sirolimus (chol-PEG 1 kDa 16.9 μg/g; chol-PEG 5 kDa 7.48 μg/g; free sirolimus 0.57 μg/g). The DL (EE) for chol-PEG 1 and 5 kDa were 2.93% (77.4%) and 3.10% (81.6%), respectively. The CMC values for the nanocarriers were similar to those previously reported in literature (3.85 × 10(-7) M for chol-PEG 1 kDa; 4.26 × 10(-7) M for chol-PEG 5 kDa). In conclusion, chol-PEG nanocarriers successfully loaded sirolimus and resulted in scleral permeation and high retention, which shows potential utility for the topical delivery of lipophilic ocular drugs.

A novel rapamycin-polymer conjugate based on a new poly(ethylene glycol) multiblock copolymer

PURPOSE

Rapamycin has demonstrated potent anti-tumor activity in preclinical and clinical studies. However, the clinical development of its formulations was hampered due to its poor solubility and undesirable distribution in vivo. Chemical modification of rapamycin presents an opportunity for overcoming the obstacles and improving its therapeutic index. The objective of this study is to develop a drug-polymer conjugate to increase the solubility and cellular uptake of rapamycin.

METHODS

We developed the rapamycin-polymer conjugate using a novel, linear, poly(ethylene glycol) (PEG) based multiblock copolymer. Cytotoxicity and cellular uptake of the rapamycin-polymer conjugate were evaluated in various cancer cells.

RESULTS

The rapamycin-polymer conjugate provides enhanced solubility in water compared with free rapamycin and shows profound activity against a panel of human cancer cell lines. The rapamycin-polymer conjugate also presents high drug loading capacity (wt% ~ 26%) when GlyGlyGly is used as a linker. Cellular uptake of the conjugate was confirmed by confocal microscopic examination of PC-3 cells that were cultured in the presence of FITC-labled polymer (FITC-polymer).

CONCLUSION

This study suggests that the rapamycin-polymer conjugate is a novel anti-cancer agent that may provide an attractive strategy for treatment of a wide variety of tumors.

Multifunctional nanomicellar systems for delivering anticancer drugs

Most anticancer drugs cause severe side effect due to the lack of selectivity for cancer cells. In recent years, new strategies of micellar systems, which design for specifically target anticancer drugs to tumors, are developed at the forefront of polymeric science. To improve efficiency of delivery and cancer specificity, considerable emphasis has been placed on the development of micellar systems with passive and active targeting. In this review article, we summarized various strategies of designing multifunctional micellar systems in the purpose of improving delivery efficiency. Micellar systems compose of a multifunctional copolymer or a mixture of two or more copolymers with different properties is a plausible approach to tuning the resulting properties and satisfied various requirements for anticancer drug delivery. It appears that multifunctional micellar systems hold great potential in cancer therapy.

Elastin-based protein polymer nanoparticles carrying drug at both corona and core suppress tumor growth in vivo

Numerous nanocarriers of small molecules depend on either non-specific physical encapsulation or direct covalent linkage. In contrast, this manuscript explores an alternative encapsulation strategy based on high-specificity avidity between a small molecule drug and its cognate protein target fused to the corona of protein polymer nanoparticles. With the new strategy, the drug associates tightly to the carrier and releases slowly, which may decrease toxicity and promote tumor accumulation via the enhanced permeability and retention effect. To test this hypothesis, the drug Rapamycin (Rapa) was selected for its potent anti-proliferative properties, which give it immunosuppressant and anti-tumor activity. Despite its potency, Rapa has low solubility, low oral bioavailability, and rapid systemic clearance, which make it an excellent candidate for nanoparticulate drug delivery. To explore this approach, genetically engineered diblock copolymers were constructed from elastin-like polypeptides (ELPs) that assemble small (<100nm) nanoparticles. ELPs are protein polymers of the sequence (Val-Pro-Gly-Xaa-Gly)n, where the identity of Xaa and n determine their assembly properties. Initially, a screening assay for model drug encapsulation in ELP nanoparticles was developed, which showed that Rose Bengal and Rapa have high non-specific encapsulation in the core of ELP nanoparticles with a sequence where Xaa=Ile or Phe. While excellent at entrapping these drugs, their release was relatively fast (2.2h half-life) compared to their intended mean residence time in the human body. Having determined that Rapa can be non-specifically entrapped in the core of ELP nanoparticles, FK506 binding protein 12 (FKBP), which is the cognate protein target of Rapa, was genetically fused to the surface of these nanoparticles (FSI) to enhance their avidity towards Rapa. The fusion of FKBP to these nanoparticles slowed the terminal half-life of drug release to 57.8h. To determine if this class of drug carriers has potential applications in vivo, FSI/Rapa was administered to mice carrying a human breast cancer model (MDA-MB-468). Compared to free drug, FSI encapsulation significantly decreased gross toxicity and enhanced the anti-cancer activity. In conclusion, protein polymer nanoparticles decorated with the cognate receptor of a high potency, low solubility drug (Rapa) efficiently improved drug loading capacity and its release. This approach has applications to the delivery of Rapa and its analogs; furthermore, this strategy has broader applications in the encapsulation, targeting, and release of other potent small molecules.

Pharmacokinetic Evaluation of a DSPE-PEG2000 Micellar Formulation of Ridaforolimus in Rat

The rapamycin analog, ridaforolimus, has demonstrated potent anti-proliferative effects in cancer treatment, and it currently is being evaluated in a range of clinical cancer studies. Ridaforolimus is an extremely lipophilic compound with limited aqueous solubility, which may benefit from formulation with polymeric micelles. Herein, we report the encapsulation of ridaforolimus in 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy-poly(ethylene glycol 2000) (DSPE-PEG₂₀₀₀) via a solvent extraction technique. Micelle loading greatly improved the solubility of ridaforolimus by approximately 40 times from 200 μg/mL to 8.9 mg/mL. The diameters of the drug-loaded micelles were 33 ± 15 nm indicating they are of appropriate size to accumulate within the tumor site via the enhanced permeability and retention (EPR) effect. The DSPE-PEG₂₀₀₀ micelle formulation was dosed intravenously to rats at 10 mg/kg and compared to a control of ridaforolimus in ethanol/PEG 400. The micelle significantly increased the half-life of ridaforolimus by 170% and decreased the clearance by 58%, which is consistent with improved retention of the drug in the plasma by the micelle formulation.

Antitumor activity of celastrol nanoparticles in a xenograft retinoblastoma tumor model

Background

Celastrol, a Chinese herbal medicine, has shown antitumor activity against various tumor cell lines. However, the effect of celastrol on retinoblastoma has not yet been analyzed. Additionally, the poor water solubility of celastrol restricts further therapeutic applications. The goal of this study was to evaluate the effect of celastrol nanoparticles (CNPs) on retinoblastoma and to investigate the potential mechanisms involved.

Methods

Celastrol-loaded poly(ethylene glycol)-block-poly(ɛ-caprolactone) nanopolymeric micelles were developed to improve the hydrophilicity of celastrol. The 2-(2-methoxy-4- nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulf-ophenyl)-2H tetrazolium monosodium salt (WST-8) assay was used to determine the inhibitory effect of CNPs on SO-Rb 50 cell proliferation in vitro. Immunofluorescence was used to evaluate the apoptotic effect of CNPs on nuclear morphology, and flow cytometry was used to quantify cellular apoptosis. The expression of Bcl-2, Bax, NF-κB p65, and phospo-NF-κB p65 proteins was assessed by Western blotting. A human retinoblastoma xenograft model was used to evaluate the inhibitory effects of CNPs on retinoblastoma in NOD-SCID mice. Hematoxylin and eosin staining was used to assess the apoptotic effects of CNPs on retinoblastoma.

Results

CNPs inhibit the proliferation of SO-Rb 50 cells in a dose- and time-dependent manner with an IC₅₀ of 17.733 μg/mL (celastrol-loading content: 7.36%) after exposure to CNPs for 48 hours. CNPs induce apoptosis in SO-Rb 50 cells in a dose-dependent manner. The expression of Bcl-2, NF-κB p65, and phospo-NF-κB p65 proteins decreased after exposure to CNPs 54.4 μg/mL for 48 hours. Additionally, the Bax/Bcl-2 ratio increased, whereas the expression of Bax itself was not significantly altered. CNPs inhibit the growth of retinoblastoma and induce apoptosis in retinoblastoma cells in mice.

Conclusion

CNPs inhibit the growth of retinoblastoma in mouse xenograft model by inducing apoptosis in SO-Rb 50 cells, which may be related to the increased Bax/Bcl-2 ratio and the inhibition of NF-κB. CNPs may represent a potential alternative treatment for retinoblastoma.

Pharmacokinetic study of 3-in-1 poly(ethylene glycol)-block-poly(D, L-lactic acid) micelles carrying paclitaxel, 17-allylamino-17-demethoxygeldanamycin, and rapamycin

Concurrent delivery of multiple poorly water-soluble anticancer drugs has been a great challenge due to the toxicities exerted by different surfactants or organic solvents used in solubilizing individual drugs. We previously found that poly(ethylene glycol)-block-poly(D, L-lactic acid) (PEG-b-PLA) micelles can serve as a safe delivery platform for simultaneous delivery of paclitaxel (PTX), 17-allylamino-17-demethoxygeldanamycin (17-AAG), and rapamycin (RAP) to mice. The high tolerance of this polymeric micelle formulation by mice allowed us to investigate the pharmacokinetics of the 3 co-delivered drugs. In this study, it was shown that 3-in-1 PEG-b-PLA micelle delivering high doses of PTX, 17-AAG, and RAP (60, 60, and 30 mg/kg, respectively) significantly increased the values of the area under the plasma concentration-time curves (AUC) of PTX and RAP in mice compared to the drugs delivered individually, while the pharmacokinetic parameters of 17-AAG were similar in both 3-in-1 and single drug-loaded PEG-b-PLA micelle formulations. Moreover, pharmacokinetic study using 2-in-1 micelles indicated that the augmented AUC value of RAP was due to the co-delivery of 17-AAG, while the increase in AUC of PTX was more likely caused by the co-delivery of RAP. In contrast, when 3-in-1 and single drug-loaded PEG-b-PLA micelles were administrated at modest dose (PTX, 17-AAG, and RAP at 10, 10, and 5 mg/kg, respectively), pharmacokinetic differences of individual drugs between 3-in-1 and single drug formulations were eliminated. These results suggest that 3-in-1 PEG-b-PLA micelles can concurrently deliver PTX, 17-AAG, and RAP without changing the pharmacokinetics of each drug at modest doses, but altered pharmacokinetic profiles emerge when drugs are delivered at higher doses.

Celastrol nanoparticles inhibit corneal neovascularization induced by suturing in rats

PURPOSE

Celastrol, a traditional Chinese medicine, is widely used in anti-inflammation and anti-angiogenesis research. However, the poor water solubility of celastrol restricts its further application. This paper aims to study the effect of celastrol nanoparticles (CNPs) on corneal neovascularization (CNV) and determine the possible mechanism.

METHODS

To improve the hydrophilicity of celastrol, celastrol-loaded poly(ethylene glycol)-block-poly(ɛ-caprolactone) nanopolymeric micelles were developed. The characterization of CNPs was measured by dynamic light scattering and transmission electron microscopy analysis. Celastrol loading content and release were assessed by ultraviolet-visible analysis and high performance liquid chromatography, respectively. In vitro, human umbilical vein endothelial cell proliferation and capillary-like tube formation were assayed. In vivo, suture-induced CNV was chosen to evaluate the effect of CNPs on CNV in rats. Immunohistochemistry for CD68 assessed the macrophage infiltration of the cornea on day 6 after surgery. Real-time quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay were used to evaluate the messenger ribonucleic acid and protein levels, respectively, of vascular endothelial growth factor, matrix metalloproteinase 9, and monocyte chemoattractant protein 1 in the cornea.

RESULTS

The mean diameter of CNPs with spherical shape was 48 nm. The celastrol loading content was 7.36%. The release behavior of CNPs in buffered solution (pH 7.4) showed a typical two-phase release profile. CNPs inhibited the proliferation of human umbilical vein endothelial cells in a dose-independent manner and suppressed the capillary structure formation. After treatment with CNPs, the length and area of CNV reduced from 1.16 ± 0.18 mm to 0.49 ± 0.12 mm and from 7.71 ± 0.94 mm(2) to 2.29 ± 0.61 mm(2), respectively. Macrophage infiltration decreased significantly in the CNP-treated corneas. CNPs reduced the expression of vascular endothelial growth factor, matrix metalloproteinase 9, and monocyte chemoattractant protein 1 in the cornea on day 6 after suturing.

CONCLUSION

CNPs significantly inhibited suture-induced CNV by suppressing macrophage infiltration and the expression of vascular endothelial growth factor and matrix metalloproteinase 9 in the rat cornea.

Nanostructure-based drug delivery systems for brain targeting

CONTEXT

It is well-known fact that blood brain barrier (BBB) hinders the penetrance and access of many pharmacotherapeutic agents to central nervous system (CNS). Many diseases of the CNS remain undertreated and the inability to treat most CNS disorders is not due to the lack of effective CNS drug discovery, rather, it is due to the ineffective CNS delivery. Therefore, a number of nanostructured drug delivery carriers have been developed and explored over the past couple of years to transport the drugs to brain.

OBJECTIVE

The present review will give comprehensive details of extensive research being done in field of nanostructured carriers to transport the drugs through the BBB in a safe and effective manner.

METHODS

The method includes both the polymeric- and lipid-based nanocarriers with emphasis on their utility, methodology, advantages, and the drugs which have been worked on using a particular approach to provide a noninvasive method to improve the drug transport through BBB.

RESULTS

Polymeric- and lipid-based nanocarriers enter brain capillaries before reaching the surface of the brain microvascular endothelial cells without the disruption of BBB. These systems are further modified with specific ligands vectors and pegylation aiming to target and enhance their binding with surface receptors of the specific tissues inside brain and increase long circulatory time which favors interaction and penetration into brain endothelial cells.

CONCLUSION

This review would give an insight to the researchers working on neurodegenerative and non-neurodegenerative diseases of the CNS including brain tumor.

Biomedical Applications of Biodegradable Polymers

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. In order to fit functional demand, materials with desired physical, chemical, biological, biomechanical and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.

Poly(ethylene glycol)-block-poly(2-methyl-2-benzoxycarbonyl-propylene carbonate) micelles for rapamycin delivery: in vitro characterization and biodistribution

Our objective was to synthesize an amphiphilic diblock copolymer for micellar delivery of rapamycin. Poly(ethylene glycol)-block-poly(2-methyl-2-benzoxycarbonyl-propylene carbonate) (PEG-b-PBC) with different hydrophobic core lengths were synthesized from methoxy poly(ethylene glycol) and 2-methyl-2-benzoxycarbonyl-propylene carbonate through ring-opening polymerization using 1,8-diazabicycloundec-7-ene as a catalyst. The critical micelle concentration of PEG-b-PBC was around 10(-8) M and depends on the hydrophobic core length. Rapamycin was effectively incorporated into micelles and drug loading increased with increasing hydrophobic core length, with maximal drug loading of 10% (w/w, drug/polymer), drug loading efficiency of about 85%, and mean particle size of around 70 nm. The drug release profile was also dependent on the hydrophobic core length and the drug release from PEG(114) -b-PBC(30) micelles was the slowest. We also determined the toxicity of rapamycin micelles on insulinoma (INS-1E) β-cells and human islets. Encapsulation of rapamycin into PEG-b-PBC micelles reduced its toxicity. Biodistribution of rapamycin-loaded PEG-b-PBC micelles was determined after systemic administration into mice. Rapamycin-loaded PEG-b-PBC micelles showed little difference in pharmacokinetics and biodistribution characteristics in mice compared with rapamycin carrying nanosuspension. In conclusion, rapamycin formulated with PEG-b-PBC micelles showed significantly reduced toxicity on INS-1E β-cells and human islets, but had similar biodistribution profiles as those of nanosuspensions.

Cell delivery of therapeutic nanoparticles

Nanomedicine seeks to manufacture drugs and other biologically relevant molecules that are packaged into nanoscale systems for improved delivery. This includes known drugs, proteins, enzymes, and antibodies that have limited clinical efficacy based on delivery, circulating half-lives, or toxicity profiles. The <100 nm nanoscale physical properties afford them a unique biologic potential for biomedical applications. Hence they are attractive systems for treatment of cancer, heart and lung, blood, inflammatory, and infectious diseases. Proposed clinical applications include tissue regeneration, cochlear and retinal implants, cartilage and joint repair, skin regeneration, antimicrobial therapy, correction of metabolic disorders, and targeted drug delivery to diseased sites including the central nervous system. The potential for cell and immune side effects has necessitated new methods for determining formulation toxicities. To realize the potential of nanomedicine from the bench to the patient bedside, our laboratories have embarked on developing cell-based carriage of drug nanoparticles to improve clinical outcomes in infectious and degenerative diseases. The past half decade has seen the development and use of cells of mononuclear phagocyte lineage, including dendritic cells, monocytes, and macrophages, as Trojan horses for carriage of anti-inflammatory and anti-infective medicines. The promise of this new technology and the perils in translating it for clinical use are developed and discussed in this chapter.

The pH-induced thermosensitive poly (NIPAAm-co-AAc-co-HEMA)-g-PCL micelles used as a drug carrier

The macromonomer of 2-hydroxyethyl methyacrylate-caprolactone (HPCL) was synthesized by the ring-opening polymerization (ROP) of epsilon-caprolactone, which was initiated by 2-hydroxyethyl methyacrylate (HEMA). Then, the graft terpolymers of NIPAAm-co-AAc-co-HEMA-g-PCL (PHNA-CL) with varying mole ratios were subsequently synthesized by free radical polymerization of HEMA-PCL, N-isopropylacrylamide (NIPAAm) and acrylic acid (AAc). PHNA-CL was further self-assembled in different types of solvent. All the as-prepared copolymers were characterized by 1H NMR, FT-IR and GPC. Micellization behaviors of micelles were studied by TEM and DLS. The micelles exhibited a phase transition temperature which can be readily adjusted by changing pH value of the micellization system. Micelle loaded with doxorubicin (DOX) was used to evaluate the drug release behavior. The release of DOX from micelles could be controlled by changing pH value and temperature in buffer solutions. The micelles are potentially to be used as a new anticancer drug carrier for intracellular delivery.

Various drug delivery approaches to the central nervous system

IMPORTANCE OF THE FIELD

The presence of the blood-brain barrier (BBB), an insurmountable obstacle, in particular, and other barriers in brain and periphery contribute to hindrance of the successful diagnosis and treatment of a myriad of central nervous system pathologies. This review discusses several strategies adopted to define a rational drug delivery approach to the CNS along with a short description of the strategies implemented by the authors' group to enhance the analgesic activity, a CNS property, of chimeric peptide of Met-enkephalin and FMRFa (YGGFMKKKFMRFa-YFa).

AREAS COVERED IN THIS REVIEW

Various approaches for drug delivery to the CNS with their beneficial and non-beneficial aspects, supported by an extensive literature survey published recently, up to August 2009.

WHAT THE READER WILL GAIN

The reader will have the privilege of gaining an understanding of previous as well as recent approaches to breaching the CNS barriers.

TAKE HOME MESSAGE

Among the various strategies discussed, the potential for efficacious CNS drug targeting in future lies either with the non-invasively administered multifunctional nanosystems or these nanosystems without characterstics such as long systemic circulating capability and avoiding reticuloendothelial system scavenging system of the body, endogenous transporters and efflux inhibitors administered by convection-enhanced delivery.

β-cyclodextrin-centered star-shaped amphiphilic polymers for doxorubicin delivery

Aim: Delivery of doxorubicin could be achieved by a novel micellar system based on β-cyclodextrin-centered star-shaped amphiphilic polymers (sPEL/CD). This study specifically explored the effect of polylactide segments in sPEL/CD on various micelle properties, such as the critical micelle concentration, size, drug loading, cytotoxicity and drug resistance reversing effect. Method: The sPEL/CD was synthesized by the arm-first method. The critical micelle concentrations of polymeric micelles were determined by fluorescence spectrophotometry using pyrene as a probe. The oil/water method was applied to prepare doxorubicin-loaded micelles. 3-(4,5-dimethylthi-azol-2-yl)-2,5-diphenyltetrazolium bromide, confocal laser-scanning microscopy and flow cytometry were used to examine cell cytotoxicity and cellular uptake of the doxorubicin-loaded micelles. Finally, rhodamine-123 cellular uptake was determined to evaluate the polymer action on MCF-7 and MCF-7/ADR cells. Results: All polymers exhibited low cytotoxicity and their micelles had a desirable release-acceleration pH (pH 5.0) for cytoplasmic drug delivery. With the introduction of polylactide into the polymer, the micelle critical micelle concentration can be effectively decreased and the drug-loading content was enhanced. Most importantly, the drug resistance of MCF-7/ADR cells was significantly reversed via the interaction between polymer and Pgp. Therefore, this type of polymer has potential superiority for cancer therapy.

Clinical toxicities of nanocarrier systems

Toxicity of nanocarrier systems involves physiological, physicochemical, and molecular considerations. Nanoparticle exposures through the skin, the respiratory tract, the gastrointestinal tract and the lymphatics have been described. Nanocarrier systems may induce cytotoxicity and/or genotoxicity, whereas their antigenicity is still not well understood. Nanocarrier may alter the physicochemical properties of xenobiotics resulting in pharmaceutical changes in stability, solubility, and pharmacokinetic disposition. In particular, nanocarriers may reduce toxicity of hydrophobic cancer drugs that are solubilized. Nano regulation is still undergoing major changes to encompass environmental, health, and safety issues. The rapid commercialization of nanotechnology requires thoughtful environmental, health and safety research, meaningful, and an open discussion of broader societal impacts, and urgent toxicological oversight action.

Paclitaxel prodrugs with sustained release and high solubility in poly(ethylene glycol)-b-poly(epsilon-caprolactone) micelle nanocarriers: pharmacokinetic disposition, tolerability, and cytotoxicity

PURPOSE

Develop a Cremophor and solvent free formulation of paclitaxel using amphiphilic block co-polymer micelles of poly(ethylene glycol)-b-poly(epsilon-caprolactone) (PEG-b-PCL) and characterize their release, solubility, cytotoxicity, tolerability, and disposition.

METHODS

Hydrophobic prodrugs of paclitaxel were synthesized via DCC/DMAP or anhydride chemistry to overcome the poor loading (<1% w/w) of paclitaxel in micelles of PEG-b-PCL. Micelles were prepared by a co-solvent extraction technique. A micellar formulation of paclitaxel prodrug (PAX7'C(6)) was dosed intravenously to rats (10 mg/kg) and compared to Taxol (paclitaxel in CrEL:EtOH) and PAX7'C(6) in CrEL:EtOH as controls at the same dose. Pharmacokinetic parameters and tissue distribution were assessed.

RESULTS

Paclitaxel prodrugs had solubilities >5 mg/ml in PEG-b-PCL micelles. Resulting PEG-b-PCL micelles contained 17-22% w/w prodrug and were less than 50 nm in diameter. PEG-b-PCL micelles released paclitaxel prodrugs over several days, t(1/2)>3 d. Only the 7'derivative of paclitaxel with the shortest acylchain 7'hexonoate (PAX7'C(6)) maintained cytotoxic activity similar to unmodified paclitaxel. PAX7'C(6) micelles demonstrated an increase in area under the curve, half-life, and mean residence time while total clearance and volume of distribution decreased.

CONCLUSIONS

Paclitaxel prodrugs in PEG-b-PCL micelle nanocarriers augment the disposition and increase tolerability making further studies on tumor efficacy warranted.