Genetic polymorphisms and their association with methotrexate polyglutamates during maintenance treatment in Korean children and young adults with acute lymphoblastic leukemia.

The aim of this study was to investigate the impact of genetic polymorphisms on methotrexate (MTX) metabolism in Korean children and young adults with acute lymphoblastic leukemia, specifically focusing on MTX polyglutamates (MTX-PGs) in erythrocytes, which have been rarely studied. Korean children and young adult patients undergoing maintenance therapy for acute lymphoblastic leukemia, who were receiving weekly oral MTX doses of 20 mg/m²/week, were prospectively included. We investigated erythrocyte MTX-PG (PG1 to PG5) levels, MTX-PG/MTX dose ratios, and 222 genetic polymorphisms spanning 78 genes and three intergenic areas related to MTX transport, folate cycle metabolism, purine/pyrimidine pathways, and non-pathway genes (including TPMT and NUDT15 genotypes) to explore their association with MTX metabolism. MTX-PG levels were associated with MTX dose (p < 0.05), and MTX-PG3 comprised the majority of the total MTX-PGs, with a median of 39.3 %. Various polymorphisms within the same gene demonstrated differing associations with each type of MTX-PG, underscoring the complexity of MTX pharmacogenetics. Among the polymorphisms examined, 14 across 13 genes showed significant associations with MTX-PG2-5 levels, even after adjusting for the false discovery rate (ABCC5, ATG16L1, CEP72, FSTL5, GMPS, HTR3A, IMPDH1, NT5C2, SLC28A3, SLCO1B3, SUCLA2, TPMT, and TYMS). This study enhances our understanding of genetic polymorphisms in MTX metabolism and therapeutic monitoring for MTX maintenance, promoting personalized medicine in acute lymphoblastic leukemia patients.

Plasma Distribution of Methotrexate and Its Polyglutamates in Pediatric Acute Lymphoblastic Leukemia: Preliminary Insights.

BACKGROUND AND OBJECTIVE: High-dose methotrexate (HD-MTX) is the mainstream therapy of current acute lymphoblastic leukemia (ALL) regimens, but frequent intra- and interindividual differences in the clinical response to HD-MTX lead to chemotherapeutic interruption or discontinuation. The exact mechanism of transport across the cell membrane and the disposition of active methotrexate metabolites-methotrexate polyglutamates (MTXPGs)-are not well described in the literature. The aim of this study was to gain more insight into the plasma distribution of methotrexate and MTXPGs in pediatric patients with ALL and to clarify the obscure pathways of MTXPGs. METHODS: We prospectively measured the concentrations of MTXPG1-7 in plasma samples from three male pediatric patients treated with HD-MTX and leucovorin rescue according to the IC-BFM 2009 protocol using liquid chromatography-mass spectrometry (LC-MS). Blood samples were obtained at 24, 36, 42, and 48 h after the start of HD-MTX treatment. RESULTS: Noticeable plasma concentrations of MTXPGs with a 2.2-fold interpatient variability were detected. The highest interindividual variability in total plasma MTXPG concentration was observed at 36 h, and ranged from 13.78 to 30.82 µmol/L. Among all patients, the predominant polyglutamate types in relation to the total plasma MTXPG concentration at each time point were MTXPG3 (16.71-30.02%) and MTXPG5 (26.23-38.60%), while MTXPG7 was the least abundant MTXPG (3.22-5.02%). CONCLUSION: The presence of MTXPGs in plasma of patients with ALL could be related to the action of ABC efflux transporters on blood cells and hepatocytes resulting from the administration of high doses of methotrexate. This study may not draw definitive conclusions, but it does reduce uncertainty about the dynamics of methotrexate and its active metabolites, which may be of vital importance for achieving a clinical response.

Maintenance therapy and risk of osteonecrosis in children and young adults with acute lymphoblastic leukemia: a NOPHO ALL2008 sub-study.

PURPOSE: Osteonecrosis is a burdensome treatment-related toxicity that is mostly diagnosed during or soon after 6-mercaptopurine (6MP)/methotrexate (MTX) maintenance therapy for acute lymphoblastic leukemia (ALL), possibly indicating a pathogenic role of these drugs. METHODS: We prospectively registered symptomatic osteonecrosis during treatment of 1234 patients aged 1.0-45.9 years treated according to the Nordic Society of Hematology and Oncology (NOPHO) ALL2008 protocol. MTX/6MP metabolites were measured as part of the NOPHO ALL2008 maintenance therapy study. RESULTS: After a median follow-up of 5.6 years [interquartile range (IQR) 3.6-7.5], 68 patients had been diagnosed with symptomatic osteonecrosis. The cumulative incidence was 2.7% [95% confidence interval (CI) 1.6-3.8%] for patients aged < 10 years, 14.9% (95% CI 9.7-20.2%) for patients aged 10.0-17.9 years, and 14.4% (95% CI 8.0-20.8%) for patients aged ≥ 18 years. The median time from diagnosis of ALL to diagnosis of osteonecrosis in these age groups was 1.0 year (IQR 0.7-2.0), 2.0 years (IQR 1.1-2.4), and 2.2 years (IQR 1.8-2.8), respectively (p = 0.001). With 17,854 blood samples available for MTX and 6MP metabolite analysis, neither erythrocyte levels of 6-thioguanine (TG) nucleotides (p > 0.99), methylated 6MP metabolites (p = 0.37), MTX polyglutamates (p = 0.98) nor DNA-TG (p = 0.53) were significantly associated with the hazard of osteonecrosis in Cox models stratified by the three age groups and adjusted for sex. CONCLUSION: Maintenance therapy intensity determined by 6MP and MTX metabolites was not associated with the risk of developing osteonecrosis in the NOPHO ALL2008 cohort.

A Radiolabeled Self-assembled Nanoparticle Probe for Diagnosis of Lung-Metastatic Melanoma.

Melanoma is a highly malignant skin cancer that frequently metastasizes to the lung, bone, and brain at an early phase. Therefore, noninvasive detection of metastasized melanoma could be beneficial to determine suitable therapeutic strategies. We previously reported a biocompatible ternary anionic complex composed of plasmid DNA (pDNA), polyethyleneimine (PEI), and γ-polyglutamic acid (γ-PGA) based on an electrostatic interaction, which was highly taken up by melanoma cells (B16-F10), even if it was negatively charged. Here, we developed a radiolabeled γ-PGA complex by using indium-111 (111In)-labeled polyamidoamine dendrimer (4th generation; G4) instead of pDNA and iodine-125 (125I)-labeled PEI instead of native PEI, and evaluated its effectiveness as a melanoma-targeted imaging probe. This ternary complex was synthesized at a theoretical charge ratio; carboxyl groups of 111In-diethylenetriaminepentaacetic acid (DTPA)-G4 : amino groups of 125I-PEI : carboxyl groups of γ-PGA was 1 : 8 : 16, and the size and zeta potential were approximately 29 nm and -33 mV, respectively. This complex was taken up by B16-F10 cells with time. Furthermore, a biodistribution study, using normal mice, demonstrated its accumulation in the liver, spleen, and lung, where macrophage cells are abundant. Almost the same level of radioactivity derived from both 111In and 125I was observed in these organs at an early phase after probe injection. Compared with the normal mice, significantly higher lung-to-blood ratios of radioactivity were observed in the B16-F10-lung metastatic cancer model. In conclusion, the radiolabeled γ-PGA complex would hold potentialities for nuclear medical imaging of lung metastatic melanoma.

Pharmacogenomics of intracellular methotrexate polyglutamates in patients' leukemia cells in vivo.

BACKGROUNDInterpatient differences in the accumulation of methotrexate's active polyglutamylated metabolites (MTXPGs) in leukemia cells influence its antileukemic effects.METHODSTo identify genomic and epigenomic and patient variables determining the intracellular accumulation of MTXPGs, we measured intracellular MTXPG levels in acute lymphoblastic leukemia (ALL) cells from 388 newly diagnosed patients after in vivo high-dose methotrexate (HDMTX) (1 g/m2) treatment, defined ALL subtypes, and assessed genomic and epigenomic variants influencing folate pathway genes (mRNA, miRNA, copy number alterations [CNAs], SNPs, single nucleotide variants [SNVs], CpG methylation).RESULTSWe documented greater than 100-fold differences in MTXPG levels, which influenced its antileukemic effects (P = 4 × 10-5). Three ALL subtypes had lower MTXPG levels (T cell ALL [T-ALL] and B cell ALL [B-ALL] with the TCF3-PBX1 or ETV6-RUNX1 fusions), and 2 subtypes had higher MTXPG levels (hyperdiploid and BCR-ABL like). The folate pathway genes SLC19A1, ABCC1, ABCC4, FPGS, and MTHFD1 significantly influenced intracellular MTXPG levels (P = 2.9 × 10-3 to 3.7 × 10-8). A multivariable model including the ALL subtype (P = 1.1 × 10-14), the SLC19A1/(ABCC1 + ABCC4) transporter ratio (P = 3.6 × 10-4), the MTX infusion time (P = 1.5 × 10-3), FPGS mRNA expression (P = 2.1 × 10-3), and MTX systemic clearance (P = 4.4 × 10-2) explained 42% of the variation in MTXPG accumulation (P = 1.1 × 10-38). Model simulations indicated that a longer infusion time (24 h vs. 4 h) was superior in achieving higher intracellular MTXPG levels across all subtypes if ALL.CONCLUSIONSThese findings provide insights into mechanisms underlying interpatient differences in intracellular accumulation of MTXPG in leukemia cells and its antileukemic effectsFUNDINGTHE National Cancer Institute (NCI) and the Institute of General Medical Sciences of the NIH, the Basque Government Programa Posdoctoral de Perfeccionamiento de Personal Investigador doctor, and the American Lebanese Syrian Associated Charities (ALSAC).

An Adjustable pH-Responsive Drug Delivery System Based on Self-Assembly Polypeptide-Modified Mesoporous Silica.

In this study, an adjustable pH-responsive drug delivery system using mesoporous silica nanoparticles (MSNs) as the host materials and the modified polypeptides as the nanovalves is reported. Since the polypeptide can self-assemble via electrostatic interaction at pH 7.4 and be disassembled by pH changes, the modified poly(l-lysine) and poly(l-glutamate) are utilized for pore blocking and opening in the study. Poly(l-lysine)-MSN (PLL-MSN) and poly(l-glutamate)-MSN (PLG-MSN) are synthesized via the ring opening polymerization of N-carboxyanhydrides onto the surface of mesoporous silica nanoparticles. The successful modification of the polypeptide on MSN is proved by Zeta potential change, X-ray photoelectron spectroscopy (XPS), solid state NMR, and MALDI-TOF MS. In vitro simulated dye release studies show that PLL-MSN and PLG-MSN can successfully load the dye molecules. The release study shows that the controlled release can be constructed at different pH by adjusting the ratio of PLL-MSN to PLG-MSN. Cellular uptake study indicates that the drug is detected in both cytoplasm and nucleus, especially in the nucleus. In vitro cytotoxicity assay indicates that DOX loaded mixture nanoparticles (ratio of PLL-MSN to PLG-MSN is 1:1) can be triggered for drug release in HeLa cells, resulting in 88% of cell killing.

Enhanced nanoparticle accumulation by tumor-acidity-activatable release of sildenafil to induce vasodilation.

Inefficient nanoparticle accumulation in solid tumors hinders the clinical translation of cancer nanomedicines. Herein, we proposed that sildenafil, a vasodilator ampholyte, could be used to promote nanoparticle accumulation by inducing vasodilation after its tumor acidity-triggered release from the nanocarriers. To confirm this, sildenafil was first encapsulated in a cisplatin-incorporated polymeric micelle. The dense PEG shell of the micelle reduced its endocytosis by cancer cells, which in return resulted in accumulative extracellular release of protonated sildenafil in the acidic tumor microenvironment. The released sildenafil was found to be more effective in enlarging the tumor blood vessels than could be achieved without sildenafil. As a result, we demonstrated considerable improvement in the intratumoral accumulation of the sildenafil-cisplatin co-loaded nanoparticle and its enhanced cancer therapeutic efficacy over the control group. Given the generality of a dense PEG shell and a hydrophobic part in most clinically developed nanomedicines, this work implies the great potential of sildenafil as a simple and universal adjuvant to selectively promote the intratumoral accumulation of nanomedicines, thus improving their clinical translation.

Targeted delivery of 20(S)-ginsenoside Rg3-based polypeptide nanoparticles to treat colon cancer.

Colorectal cancer (CRC) is a major malignancy characterized by a high metastasis rate. Systematic chemotherapy is important for patients with advanced CRC. However, many limitations (e.g., side effects to normal organs, shorter circulation time, and unsatisfactory tumor inhibition results) of traditional chemotherapy restrict its further application. Thus, it is necessary to find a method to overcome these challenges and improve the efficacy of CRC treatment. In this study, 20(S)-ginsenoside (Rg3) co-loaded poly(ethylene glycol)-block-poly(L-glutamic acid-co-L-phenylalanine) (mPEG-b-P(Glu-co-Phe)) nanoparticles (Rg3-NPs) were prepared. mPEG-b-P(Glu-co-Phe)-based drug delivery systems are pH sensitive that can target cancer cells and circulate for longer in blood. Rg3 could be released rapidly from the nanoparticles within tumor cells. A subcutaneous colon cancer mouse model was developed to evaluate the anticancer efficiency of the Rg3-NPs. The in vivo study indicated that the Rg3-NPs could significantly inhibit tumor proliferation by decreasing the expressions of proliferating cell nuclear antigen, resulting in tumor apoptosis through the increased expressions of caspase-3. Our study demonstrated the marked potential of the Rg3-NPs to treat CRC.

Macrocyclization of Interferon-Poly(α-amino acid) Conjugates Significantly Improves the Tumor Retention, Penetration, and Antitumor Efficacy.

Cyclization and polymer conjugation are two commonly used approaches for enhancing the pharmacological properties of protein drugs. However, cyclization of parental proteins often only affords a modest improvement in biochemical or cell-based in vitro assays. Moreover, very few studies have included a systematic pharmacological evaluation of cyclized protein-based therapeutics in live animals. On the other hand, polymer-conjugated proteins have longer circulation half-lives but usually show poor tumor penetration and suboptimal pharmacodynamics due to increased steric hindrance. We herein report the generation of a head-to-tail interferon-poly(α-amino acid) macrocycle conjugate circ-P(EG3Glu)20-IFN by combining the aforementioned two approaches. We then compared the antitumor pharmacological activity of this macrocycle conjugate against its linear counterparts, N-P(EG3Glu)20-IFN, C-IFN-P(EG3Glu)20, and C-IFN-PEG. Our results found circ-P(EG3Glu)20-IFN to show considerably greater stability, binding affinity, and in vitro antiproliferative activity toward OVCAR3 cells than the three linear conjugates. More importantly, circ-P(EG3Glu)20-IFN exhibited longer circulation half-life, remarkably higher tumor retention, and deeper tumor penetration in vivo. As a result, administration of the macrocyclic conjugate could effectively inhibit tumor progression and extend survival in mice bearing established xenograft human OVCAR3 or SKOV3 tumors without causing severe paraneoplastic syndromes. Taken together, our study provided until now the most relevant experimental evidence in strong support of the in vivo benefit of macrocyclization of protein-polymer conjugates and for its application in next-generation therapeutics.

Facile Formation of Gold-Nanoparticle-Loaded γ-Polyglutamic Acid Nanogels for Tumor Computed Tomography Imaging.

The formation of gold nanoparticle (Au NP)-loaded γ-polyglutamic acid (γ-PGA) nanogels (NGs) for computed tomography (CT) imaging of tumors is reported. γ-PGA with carboxyl groups activated by 1-ethyl-3-[3-(dimethylamino)propyl] carbodiimide hydrochloride is first emulsified to form NGs and then in situ chemically cross-linked with polyethylenimine (PEI)-entrapped Au NPs with partial polyethylene glycol (PEG) modification ([(Au0)200-PEI·NH2-mPEG]). The formed γ-PGA-[(Au0)200-PEI·NH2-mPEG] NGs with a size of 108.6 ± 19.1 nm display an X-ray attenuation property better than commercial iodinated small-molecular-contrast agents and can be uptaken by cancer cells more significantly than γ-PGA-stabilized single Au NPs at the same Au concentrations. These properties render the formed NGs with an ability to be used as an effective contrast agent for the CT imaging of cancer cells in vitro and a tumor model in vivo. The developed hybrid NGs may be promising for the CT imaging or theranostics of different biosystems.

Biodistribution of radiolabeled polyglutamic acid and PEG-polyglutamic acid nanocapsules.

Recently we reported the development of 100nm polyglutamic acid (PGA)-based nanocapsules, which were intended to carry anticancer drugs to the lymphatic system (Abellan-Pose et al., 2016). In this work, the objective was to further assess the potential "lympho-targeting" properties of radiolabeled 111In-PGA and 111In-PGA-PEG, following intravenous or subcutaneous administration. The results indicate that, following intravenous administration, both types of nanocapsules exhibit a modest accumulation in the lymph nodes (⩽2.3% ID/g). On the contrary, following subcutaneous administration, and irrespective of the presence of PEG on their surface, the nanocapsules were found to form a reservoir at the injection site, from which they drained slowly into the popliteal and the iliac lymph nodes. The significant accumulation of the radiolabeled nanocapsules in the lymph nodes was attained at 24 and 48h post-injection, reaching values comprised between 70% and 187% ID/g in the popliteal lymph nodes. Altogether, the results led us to validate our hypothesis about the ability of the PGA and PGA-PEG nanocapsules to reach the lymphatic system, especially following subcutaneous administration.

A comparative study of linear, Y-shaped and linear-dendritic methoxy poly(ethylene glycol)-block-polyamidoamine-block-poly(l-glutamic acid) block copolymers for doxorubicin delivery in vitro and in vivo.

UNLABELLED: The linear, Y-shaped, and linear-dendritic block copolymers of methoxy poly(ethylene glycol)-block-polyamidoamine-block-poly(l-glutamic acid) (MPEG-b-PAMAM-b-PGA) with one, two, four, and eight PGA arms but similar MPEG/PGA weight ratios (W/W) (named as P1PA, P2PA, P4PA and P8PA, respectively) were synthesized and comparatively investigated for doxorubicin hydrochloride (DOX) delivery. All the obtained block copolymers were highly biocompatible and could efficiently load DOX into nanoparticles (NPs) through electrostatic interaction. The NPs formed by linear (P1PA) or Y-shaped (P2PA) block copolymers and DOX were spherically shaped with smaller sizes, while the NPs formed from linear-dendritic block copolymers (P4PA and P8PA) were irregular in shape and larger in size. The P1PA/DOX and P2PA/DOX NPs exhibited better DOX protection and slower DOX release profile. However, cell cytotoxicity assays indicated that all the DOX-loaded NPs exhibited similar cytotoxicities with free DOX, indicating effective DOX release after cellular uptake. The NPs from linear and Y-shaped block copolymers greatly extended the blood circulation time, and displayed more accumulation in tumor site and less accumulation in the liver and kidney compared with the linear-dendritic counterparts. In addition, the P1PA/DOX and P2PA/DOX NPs also exhibited higher anti-tumor efficacy and less toxicity than the other DOX formulations. All these results indicated that the linear and Y-shaped MPEG-b-PAMAM-b-PGA block copolymers displayed better DOX delivery ability in anti-tumor treatment than the linear-dendritic copolymers. STATEMENT OF SIGNIFICANCE: Polymeric NPs derived from block copolymers have emerged as effective vehicles for drug delivery. However, the majority of the researches in this field have involved simple linear block copolymers and there are very few comparative studies on the self-assembly, in vitro, and in vivo drug delivery by the block copolymers with similar composition but different architectures. In this study, a series of linear, Y-shaped, and linear-dendritic polypeptide-based block copolymers were prepared and thoroughly investigated for DOX delivery. These block polymers loaded DOX into NPs with different sizes and morphologies, and exhibited different anti-tumor capabilities both in vitro and in vivo. The results indicated that the architecture of the block copolymers played an important role in their drug delivery behaviors.

Cellular Uptake and Cytotoxic Effect of Epidermal Growth Factor Receptor Targeted and Plitidepsin Loaded Co-Polymeric Polymersomes on Colorectal Cancer Cell Lines.

Encapsulating chemotherapy drugs in targeted nanodelivery systems is one of the most promising approaches to tackle cancer disease, avoiding side effects of common treatment. In the last decade, several nanocarriers with different nature have been tested, but polypeptide-based copolymers have attracted considerable attention for their biocompatibility, controlled and slow biodegradability as well as their low toxicity. In this work, we synthesized, characterized and evaluated poly(trimethylene carbonate)-bock-poly(L-glutamic acid) derived polymersomes, targeted to epidermal growth factor receptor (EGFR), loaded with plitidepsin and ultimately tested in HT29 and LS174T colorectal cancer cell lines for specificity and efficacy. Furthermore, morphology, physico-chemical properties and plitidepsin loading were carefully investigated. A thorough in vitro cytotoxicity analysis of the unloaded polymersomes was carried out for biocompatibility check, studying viability, cell membrane asymmetry and reactive oxygen species levels. Those cytotoxicity assays showed good biocompatibility for plitidepsin-unloaded polymersomes. Cellular uptake and cytotoxic effect of EGFR targeted and plitidepsin loaded polymersome indicated that colorectal cancer cell lines were.more sensitive to anti-EGFR-drug-loaded than untargeted drug-loaded polymersomes. Also, in both cell lines, the use of untargeted polymersomes greatly reduced plitidepsin cytotoxicity as well as the cellular uptake, indicating that the use of this targeted nanocarrier is a promising approach to tackle colorectal cancer disease and avoid the undesired effects of the usual treatment. Furthermore, in vivo assays support the in vitro conclusions that EGFR targeted polymersomes could be a good drug delivery system. This work provides a proof of concept for the use of encapsulated targeted drugs as future therapeutic treatments for cancer.

Well-Defined Star-Shaped Polyglutamates with Improved Pharmacokinetic Profiles As Excellent Candidates for Biomedical Applications.

There is a need to develop new and innovative polymer carriers to be used as drug delivery systems and/or imaging agents owing to the fact that there is no universal polymeric system that can be used in the treatment of all diseases. Additionally, limitations with existing systems, such as a lack of biodegradability and biocompatibility, inevitably lead to side effects and poor patient compliance. New polymer therapeutics based on amino acids are excellent candidates for drug delivery, as they do not suffer from these limitations. This article reports on a simple yet powerful methodology for the synthesis of 3-arm star-shaped polyglutamic acid with well-defined structures, precise molecular weights (MW), and low polydispersity (D = <1.3). These were synthesized by ring-opening polymerization (ROP) of N-carboxyanhydrides (NCA) in a divergent method from novel multifunctional initiators. Herein, their exhaustive physicochemical characterization is presented. Furthermore, preliminary in vitro evaluation in selected cell models, and exhaustive in vivo biodistribution and pharmacokinetics, highlighted the advantages of these branched systems when compared with their linear counterparts in terms of cell uptake enhancement and prolonged plasma half-life.

Polymer-doxycycline conjugates as fibril disrupters: an approach towards the treatment of a rare amyloidotic disease.

The term amyloidosis describes neurological diseases where an abnormal protein is misfolded and accumulated as deposits in organs and tissues, known as amyloid, disrupting their normal function. In the most common familial amyloid polyneuropathy (FAP), transthyretin (TTR) displays this role primarily affecting the peripheral nervous system (PNS). Advanced stages of this inherited rare amyloidosis, present as fibril deposits that are responsible for disease progression. In order to stop disease progression, herein we designed an efficient family of nanoconjugates as fibril disrupters. These polymer conjugates are based on doxycycline (doxy), already in phase II trials for Alzheimer's disease, covalently linked to poly-l-glutamic acid (PGA). The conjugates were rationally designed, looking at drug loading and drug release rate by adequate linker design, always considering the physiological conditions at the molecular target site. Conjugation of doxycycline exhibited greater potential towards TTR fibril disaggregation in vitro compared to the parent drug. Exhaustive physico-chemical evaluation of these polymer-drug conjugates concluded that drug release was unnecessary for activity, highlighting the importance of an appropriate linker. Furthermore, biodistribution studies through optical imaging (OI) and the use of radiolabelled polymer-drug conjugates demonstrated conjugate safety profile and renal clearance route of the selected PGA-doxy candidate, settling the adequacy of our conjugate for future in vivo evaluation. Furthermore, preliminary studies in an FAP in vivo model at early stages of disease development showed non-organ toxicity evidences. This nanosized-system raises a promising treatment for advanced stages of this rare amyloidotic disease, and also presents a starting point for possible application within other amyloidosis-related diseases, such as Alzheimer's disease.

Prolonged local retention of subcutaneously injected polymers monitored by noninvasive SPECT imaging.

Polymers are widely applied to drug delivery systems because polymers are generally excreted from the body more slowly than small molecules. Subcutaneous injection is one plausible means of administration. In this study, the in vivo behaviors of subcutaneously injected polymers, linear poly(glutamic acid) (Poly-Glu), acetylated dendrimer (Ac-den) and collagen peptide-conjugated dendrimer (CP-den), were investigated. Single photon emission computed tomography (SPECT) imaging was used to noninvasively monitor the in vivo behaviors. Diethylenetriaminepentaacetic acid (DTPA) was conjugated to these polymers, which were labeled with radioactive (111)In. These (111)In-DTPA-bearing polymers (Poly-Glu-DTPA, Ac-den-DTPA and CP-den-DTPA) and unconjugated DTPA were subcutaneously injected into tumor-bearing mice, which were subjected to SPECT imaging. These (111)In-DTPA-bearing polymers were largely retained at the injection site for at least 1 day, whereas the unconjugated DTPA was rapidly cleared from the whole body through excretion. Poly-Glu-DTPA and Ac-den-DTPA were partly accumulated in the kidney (and the liver), but the CP-den-DTPA was not. However, these (111)In-DTPA-bearing polymers were accumulated in the liver and the kidney following intravenous administration. These results indicate that the subcutaneously injected polymers did not largely gain substantial access to the systemic circulation, which is useful for a depot of drug around the injection site.

Radiolabeled γ-polyglutamic acid complex as a nano-platform for sentinel lymph node imaging.

We established a ternary anionic complex constructed with polyamidoamine dendrimer (4th generation; G4) modified with chelating agents (diethylenetriamine pentaacetic acid (DTPA) derivative), polyethyleneimine (PEI), and γ-polyglutamic acid (PGA) as a safe nano-platform for molecular imaging. We prepared indium-111-labeled DTPA-G4/PEI/γ-PGA, and evaluated the effectiveness as a nuclear imaging probe for sentinel lymph node (LN), the first LN that drains the primary tumor. (111)In-DTPA-G4/PEI with strong cationic charge agglutinated with erythrocytes and showed extremely high cytotoxicity. By contrast, the anionic (111)In-DTPA-G4/PEI/γ-PGA had little agglutination activity with erythrocytes and no cytotoxicity, indicating their high biocompatibility. (111)In-DTPA-G4/PEI/γ-PGA was highly taken up by macrophage cells (high populations in LNs) comparable to (111)In-DTPA-G4/PEI. The uptake mechanisms of (111)In-DTPA-G4/PEI/γ-PGA were suggested to be both phagocytosis and γ-PGA-specific pathway. Upon administration of each (111)In-labeled nano-platform into rat footpads intradermally, significantly higher radioactivity of (111)In-DTPA-G4/PEI/γ-PGA was observed in the first draining popliteal LN when compared with that of (111)In-DTPA-G4/PEI. Moreover, (111)In-DTPA-G4/PEI/γ-PGA clearly visualized the sentinel LN with single photon emission computed tomography (SPECT) compared with (111)In-DTPA-G4/PEI. Thus, (111)In-DTPA-G4/PEI/γ-PGA can be useful as a nano-platform for molecular imaging including sentinel LN imaging.

Cisplatin loaded methoxy poly (ethylene glycol)-block-Poly (L-glutamic acid-co-L-Phenylalanine) nanoparticles against human breast cancer cell.

Cisplatin (cis-diaminodichloroplatinum, CDDP) loaded methoxy poly (ethylene glycol)-block-poly (glutamic acid-co-phenyl alanine) [mPEG-b-P (Glu10 -co-Phe10 ) (PGlu10 ) and mPEG-b-P (Glu20 -co-Phe10 ) (PGlu20 )] nanoparticles with two different formulations (CDDP/PGlu10 and CDDP/PGlu20 ) are successfully developed in uniformly sizes. In 190 h, the CDDP/PGlu10 shows 30% release at physiological pH and 39% at lysosomal pH. Similarly, the CDDP/PGlu20 shows 60% release at physiological pH and 90% release at lysosomal pH. The sustained and controlled release of both formulations evidences the in vitro longevity of the nanoparticles. The cell proliferation inhibition of nanoparticles against human breast cancer cell line ZR-75-30 is dose and time dependent. Both CDDP/PGlu10 and CDDP/PGlu20 show excellent hemo compatibility as evaluated by hemolysis experiments. The in vivo fate of CDDP and CDDP loaded nanoparticles are evaluated by pharmacokinetics studies. Free CDDP underwgoes instant platinum concentration decrease after intravenous administration with 1.0 wt% left in 24 h while the CDDP loaded nanoparticles show prolonged blood circulation time with 5 wt% (CDDP/PGlu20 ) to 14 wt% (CDDP/PGlu10 ) left in 24 h. This prolonged blood circulation of CDDP loaded nanoparticles makes them as promising nanocarriers for tumor targeting delivery.

A cell-based pharmacokinetics assay for evaluating tubulin-binding drugs.

Increasing evidence reveals that traditional pharmacokinetics parameters based on plasma drug concentrations are insufficient to reliably demonstrate accurate pharmacological effects of drugs in target organs or cells in vivo. This underscores the increasing need to improve the types and qualities of cellular pharmacokinetic information for drug preclinical screening and clinical efficacy assessments. Here we report a whole cell-based method to assess drugs that disturb microtubule dynamics to better understand different formulation-mediated intracellular drug release profiles. As proof of concept for this approach, we compared the well-known taxane class of anti-microtubule drugs based on paclitaxel (PTX), including clinically familiar albumin nanoparticle-based Abraxane™, and a polymer nanoparticle-based degradable paclitaxel carrier, poly(L-glutamic acid)-paclitaxel conjugate (PGA-PTX, also known as CT-2103) versus control PTX. This in vitro cell-based evaluation of PTX efficacy includes determining the cellular kinetics of tubulin polymerization, relative populations of cells under G2 mitotic arrest, cell proliferation and total cell viability. For these taxane tubulin-binding compounds, the kinetics of cell microtubule stabilization directly correlate with G2 arrest and cell proliferation, reflecting the kinetics and amounts of intracellular PTX release. Each individual cell-based dose-response experiment correlates with published, key therapeutic parameters and taken together, provide a comprehensive understanding of drug intracellular pharmacokinetics at both cellular and molecular levels. This whole cell-based evaluating method is convenient, quantitative and cost-effective for evaluating new formulations designed to optimize cellular pharmacokinetics for drugs perturbing tubulin polymerization as well as assisting in explaining drug mechanisms of action at cellular levels.

Bio-derived poly(gamma-glutamic acid) nanogels as controlled anticancer drug delivery carriers.

We have developed a novel type of polymer nanogel loaded with anticancer drug based on bio-derived poly(gamma- glutamic acid) (gamma-PGA). gamma-PGA is a highly anionic polymer that is synthesized naturally by microbial species, most prominently in various bacilli, and has been shown to have excellent biocompatibility. Thiolated gamma-PGA was synthesized by covalent coupling between the carboxyl groups of gamma-PGA and the primary amine group of cysteamine. Doxorubicin (Dox)-loaded gamma-PGA nanogels were fabricated using the following steps: (1) an ionic nanocomplex was formed between thiolated gamma-PGA as the negative charge component, and Dox as the positive charge component; (2) addition of poly(ethylene glycol) (PEG) induced hydrogen-bond interactions between thiol groups of thiolated gamma-PGA and hydroxyl groups of PEG, resulting in the nanocomplex; and (3) disulfide crosslinked gamma-PGA nanogels were fabricated by ultrasonication. The average size and surface charge of Dox-loaded disulfide cross-linked gamma-PGA nanogels in aqueous solution were 136.3 +/- 37.6 nm and -32.5 +/- 5.3 mV, respectively. The loading amount of Dox was approximately 38.7 microgram per mg of gamma-PGA nanogel. The Dox-loaded disulfide cross-linked gamma-PGA nanogels showed controlled drug release behavior in the presence of reducing agents, glutathione (GSH) (1- 10 mM). Through fluorescence microscopy and FACS, the cellular uptake of gamma-PGA nanogels into breast cancer cells (MCF-7) was analyzed. The cytotoxic effect was evaluated using the MTT assay and was determined to be dependent on both the concentration and treatment time of gamma-PGA nanogels. The bio-derived gamma-PGA nanogels are expected to be a well-designed delivery carrier for controlled drug delivery applications.