Dendrimer-based multivalent methotrexates as dual acting nanoconjugates for cancer cell targeting

Highly regioselective 6-exo-dig iodo/bromo cyclizations of functionalized 5-amino propargyl pyrimidinones: an efficient synthesis of functionalized pteridines

The manuscript describes the highly regioselective 6-exo-dig iodo/bromo cyclization of functionalized N-propagyl-amino-pyrimidinones under ambient conditions. The cyclization afforded functionalized pteridines in excellent yields. The optimized procedures are mild, operationally simple and working successfully with different substrates. The synthesis of functionalized pteridines is of great significance because of their potential pharmacological profile.

Drug-dendrimer complexes and conjugates: Detailed furtherance through theory and experiments

Dendritic nanovectors-based drug delivery has gained significant attention in the past couple of decades. Dendrimers play a crucial role in deciding the solubility of sparingly soluble drug molecules and help in improving pharmacokinetics. A few important steps in drug delivery through dendrimers, such as drug encapsulation, formulation, and target-specific delivery, play an important role in deciding the fate of a drug molecule. It is also of prime importance to understand the interactions between a drug molecule and dendrimers at atomistic levels to decode the mechanism of action of drug-dendrimer complexes and their reliability in terms of drug delivery. Colossal progress in current experimental and computational approaches in the field has resulted in a vast amount of data that needs to be curated to be further implemented efficiently. Improved computational power has led to greater accuracy and prompt predictions of properties of drug-dendrimer complexes and their mechanism of action. The current review encapsulates the pioneering work in the field, experimental achievements in terms of drug delivery, and newer computational techniques employed in the advancement of the field.

Synthesis of Two Methotrexate Prodrugs for Optimizing Drug Loading into Liposomes

Methotrexate (MTX), a compound originally used as an anticancer drug, has also found applications in a broad variety of autoimmune disorders thanks to its anti-inflammation and immunomodulatory functions. The broad application of MTX is anyway limited by its poor solubility in biological fluids, its poor bioavailability and its toxicity. In addition, encapsulating its original form in nanoformulation is very arduous due to its considerable hydrophobicity. In this work, two strategies to efficiently encapsulate MTX into liposomal particles are proposed to overcome the limitations mentioned above and to improve MTX bioavailability. MTX solubility was increased by conjugating the molecule to two different compounds: DSPE and PEG. These two compounds commonly enrich liposome formulations, and their encapsulation efficiency is very high. By using these two prodrugs (DSPE-MTX and PEG-MTX), we were able to generate liposomes comprising one or both of them and characterized their physiochemical features and their toxicity in primary macrophages. These formulations represent an initial step to the development of targeted liposomes or particles, which can be tailored for the specific application MTX is used for (cancer, autoimmune disease or others).

Immunomodulatory potential of anticancer therapy composed of methotrexate nanoconjugate and dendritic cell‑based vaccines in murine colon carcinoma

Chemotherapy with low-molecular weight compounds, despite elimination of cancer cells, entails adverse effects. To overcome this disadvantage, innovative drug delivery systems are being developed, including conjugation of macromolecular carriers with therapeutics, e.g. a nanoconjugate of hydroxyethyl starch and methotrexate (HES-MTX). The purpose of the present study was to determine whether HES-MTX, applied as a chemotherapeutic, is able to modulate the immune response and support the antitumor response generated by dendritic cells (DCs) used subsequently as immunotherapeutic vaccines. Therefore, MTX or HES-MTX was administered, as sole treatment or combined with DC-based vaccines, to MC38 colon carcinoma tumor-bearing mice. Alterations in antitumor immune response were evaluated by multiparameter flow cytometry analyses and functional assays. The results demonstrated that the nanoconjugate possesses greater immunomodulatory potential than MTX as reflected by changes in the landscape of immune cells infiltrating the tumor and increased cytotoxicity of splenic lymphocytes. In contrast to MTX, therapy with HES-MTX as sole treatment or combined with DC-based vaccines, contributed to significant tumor growth inhibition. However, only treatment with HES-MTX and DC-based vaccines activated the systemic specific antitumor response. In conclusion, due to its immunomodulatory properties, the HES-MTX nanoconjugate could become a potent anticancer agent used in both chemo- and chemoimmunotherapeutic treatment schemes.

Multivalent HER2-binding polymer conjugates facilitate rapid endocytosis and enhance intracellular drug delivery

Incorporating targeting moieties that recognize cancer-specific cellular markers can enhance specificity of anticancer nanomedicines. The HER2 receptor is overexpressed on numerous cancers, making it an attractive target. However, unlike many receptors that trigger endocytosis upon ligand binding, HER2 is an internalization-resistant receptor. As most chemotherapeutics act on intracellular targets, this presents a significant challenge for exploiting HER2 overexpression for improved tumor killing. However, hyper-crosslinking of HER2 has been shown to override the receptor's native behavior and trigger internalization. This research co-opts this crosslinking-mediated internalization for efficient intracellular delivery of an anticancer nanomedicine - specifically a HPMA copolymer-based drug delivery system. This polymeric carrier was conjugated with a small (7 kDa) HER2-binding affibody peptide to produce a panel of polymer-affibody conjugates with valences from 2 to 10 peptides per polymer chain. The effect of valence on surface binding and uptake was evaluated separately. All conjugates demonstrated similar (nanomolar) binding affinity towards HER2-positive ovarian carcinoma cells, but higher-valence conjugates induced more rapid endocytosis, with over 90% of the surface-bound conjugate internalized within 4 h. Furthermore, this enhancement was sensitive to crowding - high surface loading reduced conjugates' ability to crosslink receptors. Collectively, this evidence strongly supports a crosslinking-mediated endocytosis mechanism. Lead candidates from this panel achieved high intracellular delivery even at picomolar treatment concentrations; untargeted HPMA copolymers required 1000-fold higher treatment concentrations to achieve similar levels of intracellular accumulation. This increased intracellular delivery also translated to a more potent nanomedicine against HER2-positive cells; incorporation of the chemotherapeutic paclitaxel into this targeted carrier enhanced cytotoxicity over untargeted polymer-drug conjugate.

Toxic Effects of Methotrexate on Rat Kidney Recovered by Crocin as a Consequence of Antioxidant Activity and Lipid Peroxidation Prevention

Background

The application of methotrexate (MTX) as a chemotherapy agent and immune system suppressant has various side effects. Crocin, a xanthine derivative plant, has many therapeutic benefits. This study was planned to assess the effect of crocin on renal toxicity of MTX in a rat model.

Methods

Forty eight rats were divided randomly into eight groups (n = 6), which received normal saline, MTX, crocin, and MTX + crocin for 28 days intraperitoneally. The levels of oxidative stress in kidney and blood serum were measured, and the kidney was analyzed histologically.

Results

MTX caused an enhancement in the levels of thiobarbituric acid reactive substances and biochemical marker (creatinine and BUN). Besides, a significant decrease was observed in tissue parameters and antioxidant capacity compared to the normal control group (p < 0.001). The crocin and crocin + MTX decreased the biochemical markers, the levels of thiobarbituric acid reactive species, and tissue parameters considerably at entire dose (12.5, 25, and 50 mg/kg) and enhanced the antioxidant capacity levels compared to the MTX group (p < 0.001).

Conclusion

Administration of crocin improves the damage caused by MTX in rats. The crocin by the establishment of balance in the levels of antioxidant prevents the damage to the renal cell membrane, and subsequently the renal damage repairs.

Multivalent nanoparticles for personalized theranostics based on tumor receptor distribution behavior

It is acknowledged that the targeting ability of multivalent ligand-modified nanoparticles (MLNs) strongly depends on the ligand spatial presentation determined by ligand valency. However, the receptor overexpression level varies between different types or stages of tumors. Thus, it is essential to explore the influence of ligand valency on the targeting ability of MLNs to tumors with different levels of receptor overexpression. In this study, a dual-acting agent raltitrexed was used as a ligand to target the folate receptor (FR). Different copies of the raltitrexed-modified multivalent dendritic polyethyleneimine ligand cluster PRn (n = 2, 4, and 8) were conjugated onto magnetic nanoparticles to form multivalent magnetic NPs (MMNs) with different valences. The in vitro studies demonstrated that Fe-PR4 was the most effective valency in the treatment of high FR overexpressing KB cells with a decentralized receptor distribution, owing to the fact that Fe-PR2 was negative in statistical rebinding and Fe-PR8 could induce steric hindrance in the limited binding area. Instead, in moderate FR overexpressing HeLa cells with clustered receptor display, the extra ligands on Fe-PR8 would facilitate statistical rebinding more beneficially. Furthermore, in in vivo tumor inhibition and targeted magnetic resonance imaging (MRI) of KB tumors and another moderate FR expressing H22 tumor, similar results were obtained with the cell experiments. Overall, the optimizable treatment effect of Fe-PRn by modulating the ligand valency based on the overexpressing tumor receptor distribution behavior supports the potential of Fe-PRn as a nanomedicine for personalized theranostics.

Anti-leukemia activity of 4-amino-2-aryl-6,9-dichlorobenzo[g]pteridines

Pteridines are bicyclic heterocyclic compounds with a pyrazino[2,3-d]pyrimidine nucleus that have shown a wide range of therapeutic utilities. Concretely, 4-aminopteridine derivatives have demonstrated both anti-inflammatory and anti-cancer properties, and some of them, such as methotrexate, are profusely used in medical practice. We have recently synthesized and tested the biological activity of a novel series of 4-amino-2-aryl-6,9-dichlorobenzo[g]pteridines, finding that they present anti-inflammatory properties, as they were able to inhibit in vitro the production of pro-inflammatory cytokines TNF-α and IL-6. Now, we have evaluated the anti-tumor potential of these compounds on HL-60 and K562 leukemia cell lines. Cells growing at exponential rate were exposed to decreasing doses of each compound, from 50 to 0.39 μM, for 24, 48, and 72 h. Cell viability was tested by MTT assay and cell death fashion determined by annexin V/propidium iodide assay. The cytotoxicity of the compounds was determined in differentiated macrophage-like HL-60 cells and in human peripheral blood mononuclear cells to evaluate the potential side effects on quiescent tumor cells and normal cells, respectively. Among the series, compounds 1a, 1b, 1g, 1j, and 1k showed anti-proliferative activity. Compounds 1j and 1k were active against both HL-60 and K562 cells, with a lower IC₅₀ against HL-60 cells. Compounds 1a, 1b, and 1g had a great cytotoxic activity against HL-60, but they were far less potent against K562 cells. None had side effects in differentiated tumor cells or in human peripheral blood mononuclear cells. In conclusion, our results demonstrate that some compounds of this series of 4-amino-2-aryl-6,9-dichlorobenzo[g]pteridines have anti-cancer properties in vitro.

Targeting Groups Employed in Selective Dendrons and Dendrimers

The design of compounds with directed action to a defined organ or tissue is a very promising approach, since it can decrease considerably the toxicity of the drug/bioactive compound. For this reason, this kind of strategy has been greatly important in the scientific community. Dendrimers, on the other hand, comprise extremely organized macromolecules with many peripheral functionalities, stepwise controlled synthesis, and defined size. These nanocomposites present several biological applications, demonstrating their efficiency to act in the pharmaceutical field. Considering that, the main purpose of this review was describing the potential of dendrons and dendrimers as drug targeting, applying different targeting groups. This application has been demonstrated through interesting examples from the literature considering the last ten years of publications.

Distributions: The Importance of the Chemist's Molecular View for Biological Materials

Characterization of materials with biological applications and assessment of physiological effects of therapeutic interventions are critical for translating research to the clinic and preventing adverse reactions. Analytical techniques typically used to characterize targeted nanomaterials and tissues rely on bulk measurement. Therefore, the resulting data represent an average structure of the sample, masking stochastic (randomly generated) distributions that are commonly present. In this Perspective, we examine almost 20 years of work our group has done in different fields to characterize and control distributions. We discuss the analytical techniques and statistical methods we use and illustrate how we leverage them in tandem with other bulk techniques. We also discuss the challenges and time investment associated with taking such a detailed view of distributions as well as the risks of not fully appreciating the extent of heterogeneity present in many systems. Through three case studies showcasing our research on conjugated polymers for drug delivery, collagen in bone, and endogenous protein nanoparticles, we discuss how identification and characterization of distributions, i.e., a molecular view of the system, was critical for understanding the observed biological effects. In all three cases, data would have been misinterpreted and insights missed if we had only relied upon spatially averaged data. Finally, we discuss how new techniques are starting to bridge the gap between bulk and molecular level analysis, bringing more opportunity and capacity to the research community to address the challenges of distributions and their roles in biology, chemistry, and the translation of science and engineering to societal challenges.

Design, synthesis and preliminary biological evaluation of 5,8-dihydropteridine-6,7-diones that induce apoptosis and suppress cell migration

Pteridines are an important class of fused heterocycles found in natural products and drug molecules, and have shown diverse biological activities. A focused library of 5,8-dihydropteridine-6,7-dione derivatives were designed and evaluated for their antiproliferative activity against MGC-803, SGC-7901, A549 and PC-3 cancer cell lines. The SARs studies highlighted the importance of the piperazine substituted 5,8-dihydropteridine-6,7-dione frameworks for the activity and revealed essential structural elements. Among these compounds, compound 5n displayed the most potent and broad-spectrum antiproliferative inhibition against the tested cell lines and was sensitive to MGC-803 cell line, slightly more potent than 5-FU. Preliminary mechanistic studies showed that compound 5n could inhibit the colony formation and migration of MGC-803 cells. Besides, flow cytometry analysis showed that compound 5n concentration-dependently induced apoptosis of MGC-803 cells. Our studies suggest that the piperazine substituted 5,8-dihydropteridine-6,7-dione frameworks may be regarded as new chemotypes for designing effective antitumor agents targeting gastric cancer cells.

Targeted delivery of thymosin beta 4 to the injured myocardium using CREKA-conjugated nanoparticles

Purpose

Thymosin beta 4 (Tβ4) has multiple beneficial facets for myocardial injury, but its efficiency is limited by the low local concentration within the infarct. Here, we established a Tβ4 delivery system for cardiac repair based on the interaction between the abundant fibrin in the infarct zone and the fibrin-targeting moiety clot-binding peptide cysteine–arginine–glutamic acid–lysine–alanine (CREKA).

Methods and results

CREKA and Tβ4 were conjugated to nanoparticles (CNP–Tβ4). In vitro binding test revealed that CNP–Tβ4 had a significant binding ability to the surface of fibrin clots when compared to the control clots (NP–Tβ4). Based on the validation of fibrin expression in the early stage of ischemia injury, CNP–Tβ4 was intravenously administered to mice with acute myocardial ischemia–reperfusion injury. CNP–Tβ4 revealed a stronger fibrin-targeting ability than the NP–Tβ4 group and accumulated mainly in the infarcted area and colocalized with fibrin. Subsequently, treatment with CNP–Tβ4 resulted in a better therapeutic effect.

Conclusion

CRKEA modification favored Tβ4 accumulation and retention in the infarcted region, leading to augmented functional benefits. Fibrin-targeting delivery system represents a generalizable platform technology for regenerative medicine.

Dual-Targeted Multifunctional Nanoparticles for Magnetic Resonance Imaging Guided Cancer Diagnosis and Therapy

Hybrid nanostructures with combined functionalities can be rationally designed to achieve synergistic effects for efficient cancer treatment. Herein, a multifunctional nanoplatform is constructed, containing an inner core of an anticancer drug MTX surrounding by a nanometer-thin layer of gold as the shell with Fe₃O₄ magnetic nanoparticles (NPs) evenly distributed in the gold layer, and the outermost hybrid LA-PEG-MTX molecules as surface coating agent (denoted as MFG-LPM NPs). This nanocomposite possesses very high drug loading capacity as the entire core is MTX and integrates magnetic- and active- targeting drug delivery, light-controlled drug release, magnetic resonance imaging (MRI), as well as photothermal and chemotherapy. With a strong near-infrared (NIR) absorbance at 808 nm, the nanocomposite enables temperature elevation and light-triggered MTX release. In vitro cytotoxicity studies indicate that the strategy of combining therapy leads to a synergistic effect with high cancer cell killing efficacy. In consistency with this, due to the high accumulation of MFG-LPM NPs at tumor site and their combinatorial chemo-photothermal effects, 100% in vivo tumor elimination can be achieved. Additionally, in vivo MRI of tumor-bearing mice demonstrates an impressive performance of MFG-LPM NPs as a T₂ contrast agent. Therefore, such multifunctional nanocomposite has the potential to serve as an excellent theranostic agent that collectively integrates multiple functions for efficient MRI guided cancer diagnosis and treatment.

Folate binding protein: therapeutic natural nanotechnology for folic acid, methotrexate, and leucovorin

Blood serum proteins play a critical role in the transport, biodistribution, and efficacy of systemically-delivered therapeutics. Here, we have investigated the concentration- and ligand-dependent aggregation of folate binding protein (FBP), focusing in particular on folic acid, an important vitamin and targeting agent; methotrexate, an antifolate drug used to treat cancer and rheumatoid arthritis; and leucovorin which is used to decrease methotrexate toxicity. We employed atomic force microscopy to characterize, on a particle-by-particle basis, the volumes of the FBP nanoparticles that form upon ligand binding. We measured the distribution of FBP nanoparticle volumes as a function of ligand concentration over physiologically- and therapeutically-relevant ranges. At physiologically-relevant concentrations, significant differences in particle volume distributions exist that we hypothesize are consistent with different trafficking mechanisms for folic acid and methotrexate. In addition, we hypothesize leucovorin is trafficked and delivered like folic acid at therapeutically-relevant concentrations. We propose that changes in dosing procedures could improve the delivery and therapeutic index for methotrexate and other folic acid-targeted drug conjugates and imaging agents. Specifically, we suggest pre-binding the drugs to FBP may provide a better formulation for drug delivery of methotrexate for both cancer and rheumatoid arthritis. This would be analogous to pre-binding paclitaxel to albumin, which is already used in the clinic.

Nanomedicine in Central Nervous System (CNS) Disorders: A Present and Future Prospective

Purpose: For the past few decades central nervous system disorders were considered as a major strike on human health and social system of developing countries. The natural therapeutic methods for CNS disorders limited for many patients. Moreover, nanotechnology-based drug delivery to the brain may an exciting and promising platform to overcome the problem of BBB crossing. In this review, first we focused on the role of the blood-brain barrier in drug delivery; and second, we summarized synthesis methods of nanomedicine and their role in different CNS disorder. Method: We reviewed the PubMed databases and extracted several kinds of literature on neuro nanomedicines using keywords, CNS disorders, nanomedicine, and nanotechnology. The inclusion criteria included chemical and green synthesis methods for synthesis of nanoparticles encapsulated drugs and, their in-vivo and in-vitro studies. We excluded nanomedicine gene therapy and nanomaterial in brain imaging. Results: In this review, we tried to identify a highly efficient method for nanomedicine synthesis and their efficacy in neuronal disorders. SLN and PNP encapsulated drugs reported highly efficient by easily crossing BBB. Although, these neuro-nanomedicine play significant role in therapeutics but some metallic nanoparticles reported the adverse effect on developing the brain. Conclusion: Although impressive advancement has made via innovative potential drug development, but their efficacy is still moderate due to limited brain permeability. To overcome this constraint,powerful tool in CNS therapeutic intervention provided by nanotechnology-based drug delivery methods. Due to its small and biofunctionalization characteristics, nanomedicine can easily penetrate and facilitate the drug through the barrier. But still, understanding of their toxicity level, optimization and standardization are a long way to go.

Methotrexate Nanoparticles Prepared with Codendrimer from Polyamidoamine (PAMAM) and Oligoethylene Glycols (OEG) Dendrons: Antitumor Efficacy in Vitro and in Vivo

The novel methotrexate-loaded nanoparticles (MTX/PGD NPs) prepared with amphiphilic codendrimer PGD from polyamidoamine and oligothylene glycol dendrons were obtained via antisolvent precipitation method augmented by ultrasonication. Based on the excellent hydrophility of PGD, the drug-loaded nanoparticles could be investigated easily with the high drug-loading content (~85.2%, w/w). The MTX/PGD NPs possessed spherical morphology, nanoscaled particle size (approximately 182.4 nm), and narrow particle size distribution. Release of MTX from MTX/PGD NPs showed a sustained release manner and completed within 48 h. Hemolytic evaluation indicated MTX/PGD NPs presented good blood compatibility, and the cytotoxicity of nanoparticles against breast cancer cells in vitro, biodistribution in tumor tissue, and antitumor efficacy in vivo were enhanced significantly compared to MTX injection. According to the higher drug-loading content, enhanced antitumor efficacy, and appropriate particle size, MTX/PGD NPs as the drug delivery systems could have potential application for cancer chemotherapy in clinic.

Development and characterization of surface engineered PPI dendrimers for targeted drug delivery

In this study, we reported folate-conjugated polypropylene imine dendrimers (FA-PPI) as efficient carrier for model anticancer drug, methotrexate (MTX), for pH-sensitive drug release, selective targeting to cancer cells, and anticancer activity. In the in vitro drug release studies this nanoconjugate of MTX showed initial rapid release followed by gradual slow release, and the drug release was found to be pH sensitive with greater release at acidic pH. The ex vivo investigations with human breast cancer cell lines, MCF-7, showed enhanced cytotoxicity of MTX-FA-PPI with significantly enhanced intracellular uptake. The biofate of nanoconjugate was determined in Wistar rat where MTX-FA-PPI showed 37.79-fold increase in the concentration of MTX in liver after 24 h in comparison with free MTX formulation.

Dendrimer-mediated approaches for the treatment of brain tumor

Worldwide, the cancer appeared as one of the most leading cause of morbidity and mortality. Among the various cancer types, brain tumors are most life threatening with low survival rate. Every year approximately 238,000 new cases of brain and other central nervous system tumors are diagnosed. The dendrimeric approaches have a huge potential for diagnosis and treatment of brain tumor with targeting abilities of molecular cargoes to the tumor sites and the efficiency of crossing the blood brain barrier and penetration to brain after systemic administration. The various generations of dendrimers have been designed as novel targeted drug delivery tools for new therapies including sustained drug release, gene therapy, and antiangiogenic activities. At present era, various types of dendrimers like PAMAM, PPI, and PLL dendrimers validated them as milestones for the treatment and diagnosis of brain tumor as well as other cancers. This review highlights the recent research, opportunities, advantages, and challenges involved in development of novel dendrimeric complex for the therapy of brain tumor.

Modular Integration of Upconverting Nanocrystal-Dendrimer Composites for Folate Receptor-Specific NIR Imaging and Light-Triggered Drug Release

Upconversion nanocrystals (UCNs) display near-infrared (NIR)-responsive photoluminescent properties for NIR imaging and drug delivery. The development of effective strategies for UCN integration with other complementary nanostructures for targeting and drug conjugation is highly desirable. This study reports on a core/shell-based theranostic system designed by UCN integration with a folate (FA)-conjugated dendrimer for tumor targeting and with photocaged doxorubicin as a cytotoxic agent. Two types of UCNs (NaYF4:Yb/Er (or Yb/Tm); diameter = ≈50 to 54 nm) are described, each displaying distinct emission properties upon NIR (980 nm) excitation. The UCNs are surface modified through covalent attachment of photocaged doxorubicin (ONB-Dox) and a multivalent FA-conjugated polyamidoamine (PAMAM) dendrimer G5(FA)6 to prepare UCN@(ONB-Dox)(G5FA). Surface plasmon resonance experiments performed with G5(FA)6 dendrimer alone show nanomolar binding avidity (KD = 5.9 × 10(-9) M) to the folate binding protein. This dendrimer binding corresponds with selective binding and uptake of UCN@(ONB-Dox)(G5FA) by FAR-positive KB carcinoma cells in vitro. Furthermore, UCN@(ONB-Dox)(G5FA) treatment of FAR(+) KB cells inhibits cell growth in a light dependent manner. These results validate the utility of modularly integrated UCN-dendrimer nanocomposites for cell type specific NIR imaging and light-controlled drug release, thus serving as a new theranostic system.

Relationship between Targeting Efficacy of Liposomes and the Dosage of Targeting Antibody Using Surface Plasmon Resonance

Surface plasmon resonance (SPR) was used in this research to investigate the targeting efficacy (i.e., the binding affinity) of antibody-modified liposomes. The results indicated that liposomes modified by targeting antibodies exhibited an increase in apparent binding affinity, a result attributed to the avidity effect. More specifically, the targeting effect improved as the surface density of the targeting antibody increased, an increase primarily attributed to the decrease of the dissociation rate. However, this trend stopped when the surface density reached a threshold of approximately 1.5 × 10(8) antibody/mm(2). This surface density was found to be quite consistent regardless of the liposome size and the type of targeting antibody. In addition, a traditional cell binding experiment was conducted to confirm the saturation point obtained from SPR.

The therapeutic effect of methotrexate-conjugated Pluronic-based polymeric micelles on the folate receptor-rich tumors treatment

The therapeutic effect of methotrexate (MTX)-conjugated Pluronic-based polymeric mixed micelles (F127/P105-MTX) on the folate receptor-overexpressing tumors treatment was investigated in this study. Due to its high structural similarity to folic acid and the high expression of folate receptor in most solid tumors, MTX serves as not only a cytotoxic agent but also a homing ligand. Cellular uptake and the endocytic mechanism studies of MTX-conjugated mixed micelles were performed in folate receptor-rich KBv and folate receptor-deficient A-549 cancer cells. Additionally, the efficacy and safety studies of F127/P105-MTX in KBv tumor-bearing mice were evaluated. Results indicate that F127/P105-MTX significantly enhanced the cellular uptake in KBv cells as compared to that of conventional non-MTX-conjugated mixed micelles. Moreover, the results showed that F127/P105-MTX can be internalized by both caveolae- and clathrin-mediated endocytosis in energy-dependent and folate receptor-dependent manners. The in vitro and in vivo antitumor efficacies of F127/P105-MTX were significantly enhanced in comparison with MTX-entrapped mixed micelles. Furthermore, no acute toxicities to hematological system and major organs have been observed after intravenous administration during the regimen. Therefore, our results suggest that F127/P105-MTX could be an effective and safe nano-drug delivery system for cancer therapy, especially for the folate receptor-rich cancer treatment.

Mechanisms and implications of dual-acting methotrexate in folate-targeted nanotherapeutic delivery

The rational design of a nanoplatform in drug delivery plays a crucial role in determining its targeting specificity and efficacy in vivo. A conventional approach relies on the surface conjugation of a nanometer-sized particle with two functionally distinct types of molecules, one as a targeting ligand, and the other as a therapeutic agent to be delivered to the diseased cell. However, an alternative simplified approach can be used, in which a single type of molecule displaying dual function as both a targeting ligand and therapeutic agent is conjugated to the nanoparticle. In this review, we evaluate the validity of this new strategy by using methotrexate, which displays multifunctional mechanisms of action. Methotrexate binds to the folate receptor, a surface biomarker frequently overexpressed in tumor cells, and also inhibits dihydrofolate reductase, an enzyme critical for cell survival and division. Thus we describe a series of fifth generation poly(amido amine) dendrimers conjugated with methotrexate, and discuss several lines of evidence supporting the efficacy of this new platform strategy based on surface plasmon resonance spectroscopy, enzyme activity assays, and cell-based studies with folate receptor (+) KB cancer cells.

Supramolecular anticancer drug delivery systems based on linear–dendritic copolymers

The combination of two generations of polymers as linear–dendritic copolymers leads to hybrid systems with unique properties, which are of great interest for many applications. Herein, recent advances in anticancer drug delivery systems based on linear–dendritic copolymers have been reviewed.

5-Fluorouracil-lipid conjugate: potential candidate for drug delivery through encapsulation in hydrophobic polyester-based nanoparticles

The encapsulation of 5-fluorouracil (5-FU) in hydrophobic polymeric materials is made feasible by a lipid-based prodrug approach. A lipid-5-FU conjugate of 5-FU with palmitic acid was synthesized in two-step process. A synthesized dipalmitoyl derivative (5-FUDIPAL) was characterized using Fourier transform infrared spectroscopy and (1)H-nuclear magnetic resonance. The 5-FUDIPAL was encapsulated in polyester-based polymers by the double emulsion-solvent evaporation method. The nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy and dynamic light scattering. The thermal stability was assessed by differential scanning calorimetry data. In vitro release kinetics measurements of the drug from nanoparticles showed the controlled release pattern over a period of time. Cytotoxicity measurements by MTT assay confirmed that dipalmitoyl derivative in nano formulation successfully inhibited the cell growth. Thus the combined physical and biological evaluation of the different polyester-based nanoparticle containing the modified drug showed a facile approach to delivering 5-FU to the tumour site with enhanced efficacy.

Poly(amidoamine) dendrimer-methotrexate conjugates: the mechanism of interaction with folate binding protein

Generation 5 poly(amidoamine) (G5 PAMAM) methotrexate (MTX) conjugates employing two small molecular linkers, G5-(COG-MTX)_n, G5-(MFCO-MTX)_n were prepared along with the conjugates of the G5-G5 (D) dimer, D-(COG-MTX)_n, D-(MFCO-MTX)_n. The monomer G5-(COG-MTX)_n conjugates exhibited only a weak, rapidly reversible binding to folate binding protein (FBP) consistent with monovalent MTX binding. The D-(COG-MTX)_n conjugates exhibited a slow onset, tight-binding mechanism in which the MTX first binds to the FBP, inducing protein structural rearrangement, followed by polymer–protein van der Waals interactions leading to tight-binding. The extent of irreversible binding is dependent on total MTX concentration and no evidence of multivalent MTX binding was observed.

Nanoparticle multivalency counterbalances the ligand affinity loss upon PEGylation

The conjugation of receptor ligands to shielded nanoparticles is a widely used strategy to precisely control nanoparticle-cell interactions. However, it is often overlooked that a ligand's affinity can be severely impaired by its attachment to the polyethylene glycol (PEG) chains that are frequently used to protect colloids from serum protein adsorption. Using the model ligand EXP3174, a small-molecule antagonist for the angiotensin II receptor type 1 (AT1R), we investigated the ligand's affinity before and after its PEGylation and when attached to PEGylated nanoparticles. The PEGylated ligand displayed a 580-fold decreased receptor affinity compared to the native ligand. Due to their multivalency, the nanoparticles regained a low nanomolar receptor affinity, which is in the range of the affinity of the native ligand. Moreover, a four orders of magnitude higher concentration of free ligand was required to displace PEGylated nanoparticles carrying EXP3174 from the receptor. On average, one nanoparticle was decorated with 11.2 ligand molecules, which led to a multivalent enhancement factor of 22.5 compared to the monovalent PEGylated ligand. The targeted nanoparticles specifically bound the AT1R and showed no interaction to receptor negative cells. Our study shows that the attachment of a small-molecule ligand to a PEG chain can severely affect its receptor affinity. Concomitantly, when the ligand is tethered to nanoparticles, the immense avidity greatly increases the ligand-receptor interaction. Based on our results, we highly recommend the affinity testing of receptor ligands before and after PEGylation to identify potent molecules for active nanoparticle targeting.

Nanodrug delivery in reversing multidrug resistance in cancer cells

Different mechanisms in cancer cells become resistant to one or more chemotherapeutics is known as multidrug resistance (MDR) which hinders chemotherapy efficacy. Potential factors for MDR includes enhanced drug detoxification, decreased drug uptake, increased intracellular nucleophiles levels, enhanced repair of drug induced DNA damage, overexpression of drug transporter such as P-glycoprotein(P-gp), multidrug resistance-associated proteins (MRP1, MRP2), and breast cancer resistance protein (BCRP). Currently nanoassemblies such as polymeric/solid lipid/inorganic/metal nanoparticles, quantum dots, dendrimers, liposomes, micelles has emerged as an innovative, effective, and promising platforms for treatment of drug resistant cancer cells. Nanocarriers have potential to improve drug therapeutic index, ability for multifunctionality, divert ABC-transporter mediated drug efflux mechanism and selective targeting to tumor cells, cancer stem cells, tumor initiating cells, or cancer microenvironment. Selective nanocarrier targeting to tumor overcomes dose-limiting side effects, lack of selectivity, tissue toxicity, limited drug access to tumor tissues, high drug doses, and emergence of multiple drug resistance with conventional or combination chemotherapy. Current review highlights various nanodrug delivery systems to overcome mechanism of MDR by neutralizing, evading, or exploiting the drug efflux pumps and those independent of drug efflux pump mechanism by silencing Bcl-2 and HIF1α gene expressions by siRNA and miRNA, modulating ceramide levels and targeting NF-κB. “Theragnostics” combining a cytotoxic agent, targeting moiety, chemosensitizing agent, and diagnostic imaging aid are highlighted as effective and innovative systems for tumor localization and overcoming MDR. Physical approaches such as combination of drug with thermal/ultrasound/photodynamic therapies to overcome MDR are focused. The review focuses on newer drug delivery systems developed to overcome MDR in cancer cell.

Evaluating binding avidities of populations of heterogeneous multivalent ligand-functionalized nanoparticles

Ligand-functionalized, multivalent nanoparticles have been extensively studied as targeted carriers in biomedical applications for drug delivery and imaging. The chemical synthesis method used, however, generates nanoparticles that are heterogeneous with respect to the number of ligands on each nanoparticle. This article examines the role this heterogeneity in ligand number plays in multivalent interactions between nanoparticle ligands and targeted receptors. We designed and synthesized a model heterogeneous multivalent nanoparticle system and developed a unique kinetic analysis to quantify the avidity interactions. This system used mono-dispersed poly(amidoamine) (PAMAM) dendrimers that were then chemically functionalized with ssDNA oligonucleotides as to yield the heterogeneous nanoparticle platform (ligand valencies n = 1.7, 3.1, 6), and employed complementary oligonucleotides as targeted receptors on a surface plasmon resonance (SPR) biosensor to evaluate the multivalent binding of the nanoparticle population. Kinetic analysis of both parallel initial rate and dual-Langmuir analyses of SPR binding curves was performed to assess avidity distributions. We found that batches of multivalent nanoparticles contain both fast- and slow-dissociation subpopulations, which can be characterized as having "weak" and "strong" surface interactions ("binding"), respectively. Furthermore, we found that the proportion of "strong" binders increased as a function of the mean oligonucleotide valence of the nanoparticle population. These analyses allowed an assessment of how avidity distributions are modulated by the number of functionalized ligands and suggested that there are threshold valences that differentiated fast- and slow-dissociation nanoparticles.

Pharmacoinformatic approaches to understand complexation of dendrimeric nanoparticles with drugs

Nanoparticle based drug delivery systems are gaining popularity due to their wide spectrum advantages over traditional drug delivery systems; among them, dendrimeric nano-vectors are the most widely explored carriers for pharmaceutical and biomedical applications. The precise mechanism of encapsulation of drug molecules inside the dendritic matrix, delivery of drugs into specific cells, interactions of nano-formulation with biological targets and proteins, etc. present a substantial challenge to the scientific understanding of the subject. Computational methods complement experimental techniques in the design and optimization of drug delivery systems, thus minimizing the investment in drug design and development. Significant progress in computer simulations could facilitate an understanding of the precise mechanism of encapsulation of bioactive molecules and their delivery. This review summarizes the pharmacoinformatic studies spanning from quantum chemical calculations to coarse-grained simulations, aimed at providing better insight into dendrimer-drug interactions and the physicochemical parameters influencing the binding and release mechanism of drugs.

Multimodal SPION-CREKA peptide based agents for molecular imaging of microthrombus in a rat myocardial ischemia-reperfusion model

Microthrombosis plays a key role in many cardiovascular diseases. Although it is not difficult to localize thrombus within large or middle-sized vessels, the noninvasive diagnostic regimen for the detection of microthrombus remains scarce. Here we developed a nanoagent by conjucting superparamagnetic iron-oxide nanoparticle with fluorophore and a targeting element, CREKA, a peptide with special affinity for fibrin. In a rat model of myocardial ischemia-reperfusion (MI/R), the multimodal nanoagents were readily and selectively accumulated within microthrombosis, which was detectable by both magnetic resonance and optical imaging modalities. The fibrin-targeted nanoagent could be expected to have utility not only in molecular imaging of fibrin, understanding the mechanisms of microcirculation disorders, but also in targeted therapy with fibrinolytic agents.

Nanotechnology-based intelligent drug design for cancer metastasis treatment

Traditional chemotherapy used today at clinics is mainly inherited from the thinking and designs made four decades ago when the Cancer War was declared. The potency of those chemotherapy drugs on in-vitro cancer cells is clearly demonstrated at even nanomolar levels. However, due to their non-specific effects in the body on normal tissues, these drugs cause toxicity, deteriorate patient's life quality, weaken the host immunosurveillance system, and result in an irreversible damage to human's own recovery power. Owing to their unique physical and biological properties, nanotechnology-based chemotherapies seem to have an ability to specifically and safely reach tumor foci with enhanced efficacy and low toxicity. Herein, we comprehensively examine the current nanotechnology-based pharmaceutical platforms and strategies for intelligent design of new nanomedicines based on targeted drug delivery system (TDDS) for cancer metastasis treatment, analyze the pros and cons of nanomedicines versus traditional chemotherapy, and evaluate the importance that nanomaterials can bring in to significantly improve cancer metastasis treatment.

Avidity modulation of folate-targeted multivalent dendrimers for evaluating biophysical models of cancer targeting nanoparticles

We investigated two types of generation 5 polyamidoamine (PAMAM) dendrimers, each conjugated stochastically with a mean number of 5 or 10 methotrexate (MTX) ligands per dendrimer (G5-MTX5, G5-MTX10), for their binding to surface-immobilized folate binding protein (FBP) as a function of receptor density. The binding study was performed under flow by surface plasmon resonance spectroscopy. Two multivalent models were examined to simulate binding of the dendrimer to the receptor surface, showing that at relatively high receptor density, both dendrimer conjugates exhibit high avidity. However, upon reducing the receptor density by a factor of 3 and 13 relative to the high density level, the avidity of the lower-valent G5-MTX5 decreases by up to several orders of magnitude (KD = nM to μM), whereas the avidity of G5-MTX10 remains largely unaffected regardless of the density variation. Notably, on the 13-fold reduced FBP surface, G5-MTX5 displays binding kinetics similar to that of monovalent methotrexate, which is patently different from the still tight binding of the higher-valent G5-MTX10. Thus, the binding analysis demonstrates that avidity displayed by multivalent MTX conjugates varies in response to the receptor density and can be modulated for achieving tighter, more specific binding to the higher receptor density by modulation of ligand valency. We believe this study provides experimental evidence supportive of the mechanistic hypothesis of multivalent NP uptake to a cancer cell over a healthy cell where the diseased cell expresses the folate receptor at higher density.

Receptor-based targeting of therapeutics

Receptor-based targeting of therapeutics may be a fascinating proposition to improve the therapeutic efficacy of encapsulated drugs. The development of safe and effective nanomedicines is a prerequisite in the current nanotechnological scenario. Currently, the surface engineering of nanocarriers has attracted great attention for targeted therapeutic delivery by selective binding of targeting ligand to the specific receptors present on the surface of cells. In this review, we have discussed the current status of various receptors such as transferrin, lectoferrin, lectin, folate, human EGF receptor, scavenger, nuclear and integrin, which are over-expressed on the surface of cancer cells; along with the relevance of targeted delivery systems such as nanoparticles, polymersomes, dendrimers, liposomes and carbon nanotubes. The review also focuses on the effective utilization of receptor-based targeted delivery systems for the management of cancer in effective ways by minimizing the drug-associated side effects and improving the therapeutic efficacy of developed nano-architectures.

Paclitaxel-conjugated PAMAM dendrimers adversely affect microtubule structure through two independent modes of action

Paclitaxel (Taxol) is an anticancer drug that induces mitotic arrest via microtubule hyperstabilization but causes side effects due to its hydrophobicity and cellular promiscuity. The targeted cytotoxicity of hydrophilic paclitaxel-conjugated polyamidoamine (PAMAM) dendrimers has been demonstrated in cultured cancer cells. Mechanisms of action responsible for this cytotoxicity are unknown, that is, whether the cytotoxicity is due to paclitaxel stabilization of microtubules, as is whether paclitaxel is released intracellularly from the dendrimer. To determine whether the conjugated paclitaxel can bind microtubules, we used a combination of ensemble and single microtubule imaging techniques in vitro. We demonstrate that these conjugates adversely affect microtubules by (1) promoting the polymerization and stabilization of microtubules in a paclitaxel-dependent manner, and (2) bundling preformed microtubules in a paclitaxel-independent manner, potentially due to protonation of tertiary amines in the dendrimer interior. Our results provide mechanistic insights into the cytotoxicity of paclitaxel-conjugated PAMAM dendrimers and uncover unexpected risks of using such conjugates therapeutically.

Synthesis, characterization and target protein binding of drug-conjugated quantum dots in vitro and in living cells

Elucidation of unknown target proteins of a drug is of great importance in understanding cell biology and drug discovery. There have been extensive studies to discover and identify target proteins in the cell. Visualization of targets using drug-conjugated probes has been an important approach to gathering mechanistic information of drug action at the cellular level. As quantum dot (QD) nanocrystals have attracted much attention as a fluorescent probe in the bioimaging area, we prepared drug-conjugated QD to explore the potential of target discovery. As a model drug, we selected a well-known anticancer drug, methotrexate (MTX), which has been known to target dihydrofolate reductase (DHFR) with high affinity binding (K(d) = 0.54 nM). MTX molecules were covalently attached to amino-PEG-polymer-coated QDs. Specific interactions of MTX-conjugated QDs with DHFR were identified using agarose gel electrophoresis and fluorescence microscopy. Cellular uptake of the MTX-conjugated QDs in living CHO cells was investigated with regard to their localization and distribution pattern. MTX-QD was found to be internalized into the cells via caveolae-medicated endocytosis without significant sequestration in endosomes. A colocalization experiment of the MTX-QD conjugate with antiDHFR-TAT-QD also confirmed that MTX-QD binds to the target DHFR. This study showed the potential of the drug-QD conjugate to identify or visualize drug-target interactions in the cell, which is currently of great importance in the area of drug discovery and chemical biology.

Dendrimer-based multivalent vancomycin nanoplatform for targeting the drug-resistant bacterial surface

Vancomycin represents the preferred ligand for bacteria-targeting nanosystems. However, it is inefficient for emerging vancomycin-resistant species because of its poor affinity to the reprogrammed cell wall structure. This study demonstrates the use of a multivalent strategy as an effective way for overcoming such an affinity limitation in bacteria targeting. We designed a series of fifth generation (G5) poly(amidoamine) (PAMAM) dendrimers tethered with vancomycin at the C-terminus at different valencies. We performed surface plasmon resonance (SPR) studies to determine their binding avidity to two cell wall models, each made with either a vancomycin-susceptible (D)-Ala-(D)-Ala or vancomycin-resistant (D)-Ala-(D)-Lac cell wall precursor. These conjugates showed remarkable enhancement in avidity in the cell wall models tested, including the vancomycin-resistant model, which had an increase in avidity of four to five orders of magnitude greater than free vancomycin. The tight adsorption of the conjugate to the model surface corresponded with its ability to bind vancomycin-susceptible Staphylococcus aureus bacterial cells in vitro as imaged by confocal fluorescent microscopy. This vancomycin platform was then used to fabricate the surface of iron oxide nanoparticles by coating them with the dendrimer conjugates, and the resulting dendrimer-covered magnetic nanoparticles were demonstrated to rapidly sequester bacterial cells. In summary, this article investigates the biophysical basis of the tight, multivalent association of dendrimer-based vancomycin conjugates to the bacterial cell wall, and proposes a potential new use of this nanoplatform in targeting Gram-positive bacteria.

Targeting receptor-mediated endocytotic pathways with nanoparticles: rationale and advances

Targeting of drugs and their carrier systems by using receptor-mediated endocytotic pathways was in its nascent stages 25 years ago. In the intervening years, an explosion of knowledge focused on design and synthesis of nanoparticulate delivery systems as well as elucidation of the cellular complexity of what was previously-termed receptor-mediated endocytosis has now created a situation when it has become possible to design and test the feasibility of delivery of highly specific nanoparticle drug carriers to specific cells and tissue. This review outlines the mechanisms governing the major modes of receptor-mediated endocytosis used in drug delivery and highlights recent approaches using these as targets for in vivo drug delivery of nanoparticles. The review also discusses some of the inherent complexity associated with the simple shift from a ligand-drug conjugate versus a ligand-nanoparticle conjugate, in terms of ligand valency and its relationship to the mode of receptor-mediated internalization.