Folate-Conjugated Micelles and Their Folate-Receptor-Mediated Endocytosis

Folic acid-mediated enhancement of the diagnostic potential of luminescent europium-doped hydroxyapatite nanocrystals for cancer biomaging

Early and accurate cancer diagnosis is crucial for improving patient survival rates. Luminescent nanoparticles have emerged as a promising tool in fluorescence bioimaging for cancer diagnosis. To enhance diagnostic accuracy, ligands promoting endocytosis into cancer cells are commonly incorporated onto nanoparticle surfaces. Folic acid (FA) is one such ligand, known to specifically bind to folate receptors (FR) overexpressed in various cancer cells such as cervical and ovarian carcinoma. Therefore, surface modification of luminescent nanoparticles with FA can enhance both luminescence efficiency and diagnostic accuracy. In this study, luminescent europium-doped hydroxyapatite (EuHAp) nanocrystals were prepared via hydrothermal method and subsequently modified with (3-Aminopropyl)triethoxysilane (APTES) followed by FA to target FR-positive human cervical adenocarcinoma cell line (HeLa) cells. The sequential grafting of APTES and then FA formed a robust covalent linkage between the nanocrystals and FA. Rod-shaped FA-modified EuHAp nanocrystals, approximately 100 nm in size, exhibited emission peaks at 589, 615, and 650 nm upon excitation at 397 nm. Despite a reduction in photoluminescence intensity following FA modification, fluorescence microscopy revealed a remarkable 120-fold increase in intensity compared to unmodified EuHAp, attributed to the enhanced uptake of FA-modified EuHAp. Additionally, confocal microscope observations confirmed the specificity and the internalization of FA-modified EuHAp nanocrystals in HeLa cells. In conclusion, the modification of EuHAp nanocrystals with FA presents a promising strategy to enhance the diagnostic potential of cancer bioimaging probes.

Folate Functionalized and Evodiamine-Loaded Pluronic Nanomicelles for Augmented Cervical Cancer Cell Killing

Evodiamine (Evo) is a natural, biologically active plant alkaloid with wide range of pharmacological activities. In the present study Evo-loaded folate-conjugated Pluronic F108 nano-micelles (ENM) is synthesized to enhance the therapeutic efficacy of Evo against cervical cancer. ENM are synthesized, physicochemically characterized and in vitro anticancer activity is performed. The study demonstrates that ENM have nanoscale size (50.33 ± 3.09 nm), monodispersity of 0.122 ± 0.072, with high drug encapsulation efficiency (71.30 ± 3.76%) and controlled drug release at the tumor microenvironment. ENM showed dose-dependent and time-dependent cytotoxicity against HeLa human cervical cancer cells. The results of in vitro anticancer studies demonstrated that ENM have significant anticancer effects and greatly induce apoptosis as compared to pure Evo. The cellular uptake study suggests that increased anticancer activity of ENM is due to the improved intracellular delivery of Evo through overexpressed folate receptors. Overall, the designed ENM can be a potential targeted delivery system for hydrophobic anticancer bioactive compound like Evo.

Lysine-embedded cellulose-based nanosystem for efficient dual-delivery of chemotherapeutics in combination cancer therapy

Combination therapy by two or multiple drugs with different mechanisms of action is a promising strategy in cancer treatment. In this regard, a wide range of chemotherapeutics has used simultaneously to achieve the synergistic effect and overcome the adverse side effects of single-drug therapy. Herein, we developed a biocompatible nanoparticle-based system composed of nanocrystalline cellulose (NCC) and amino acid l-lysine for efficient co-delivery of model chemotherapeutic methotrexate (MTX) and polyphenol compound curcumin (CUR) to the MCF-7 and MDA-MB-231 cells. The drugs could release in a sustained and acidic-facilitate manner. In vitro cytotoxicity results represented the superior anti-tumor efficacy of the dual-drug-loaded nanocarriers. Possible inhibition of cell growth and induction of apoptosis in the cells treated with different formulations of CUR and MTX were explored by cell cycle analysis and DAPI staining. Overall, the engineered nanosystem can be used as suitable candidates to achieve efficient multi-drug delivery for combination cancer therapy.

LHRH-conjugated, PEGylated, poly-lactide-co-glycolide nanocapsules for targeted delivery of combinational chemotherapeutic drugs Docetaxel and Quercetin for prostate cancer

One of the major challenges in effective cancer chemotherapy is the severe systemic cytotoxicities of anticancer drugs on healthy tissues. The present study reports chemically modified polymeric nanocapsules (NCs) encapsulating combination of chemotherapeutic drugs Docetaxel (DTX) and Quercetin (QU) for its active targeting to prostate cancer (PCa). The active targeting was achieved by conjugating Luteinizing-hormone-releasing hormone (LHRH) ligand to poly-lactide-co-glycolide (PLGA) using polyethylene glycol (PEG) as a spacer. The structure of the conjugates was characterized and confirmed using ¹H NMR and ATR-FTIR. The drug encapsulated NCs showed a homogenous size distribution with their size ranging between 120 and 150 nm, and exhibited a negative zeta potential in the range of -20 to -40 mV. The in vitro release studies highlighted the sustained drug release pattern from the respective NCs; while the PEG coating to polymeric NCs provided serum stability to the NCs. The in vitro biological evaluation of the NCs was conducted using PC-3 and LNCaP cell lines. The results of the cellular uptake studies showed a significantly higher untake of the LHRH targeted NCs, while the LHRH-targeted-PEGylated DTX: QU NCs exhibited higher caspase-3 activity. The cell viability assay results showed the enhanced cell inhibition activity of the combinatorial DTX: QU when compared to individual DTX. Further, higher cell cytotoxicity was achieved by LHRH-targeted DTX: QU NCs as compared to their free-form or non-targeted NCs. Finally, the results of in vivo tumor localization and in vivo antitumor activity studies complimented and upheld the in vitro results, demonstrating the beneficial role of PLGA-PEG-LHRH NCs encapsulating combination of DTX and QU in combating prostate cancer (PCa).

Ultrasound-Triggered Destruction of Folate-Functionalized Mesoporous Silica Nanoparticle-Loaded Microbubble for Targeted Tumor Therapy

A multifunctional drug delivery vehicle, which combines the active targeted mesoporous silica nanoparticle (MSN) and microbubble (MB) drug delivery system, is proposed and fabricated. The resulting delivery vehicle integrates the merits of high drug loading capacity, multitargeting, and ultrasound-guided releasing. Folate (FA), which serves as an active ligand, is modified to the surface of MSN (MSN-FA) to enhance cell membrane translocation. MSN-FA is loaded with tanshinone IIA (TAN), then encapsulated in a microbubble (denoted as MSN-FA-TAN-MB) for more precise tumor targeting. The conjunction between FA and MSN is confirmed by fourier transform infrared spectroscopy (FTIR). The characteristics and morphology of MSN-FA-TAN-MB are investigated by confocal microscopy and transmission electron microscopy. In vitro cytotoxicity and cellular uptake studies of MSN-FA-TAN-MB are conducted on A549 and HeLa tumor cells. FA-facilitated MSN-FA-TAN uptake is shown by HeLa cells that overexpress FA receptors via a FA-receptor-mediated endocytosis mechanism. The ultrasound response property of MSN-FA-TAN-MB is also verified. MSN-FA-TAN-MB shows significant antitumor efficacy in vivo with the assistance of FA, MB, and an external ultrasound irradiation. Thus, this multifunctional vehicle may provide a novel strategy for tumor targeting and imaging in tumor therapy.

Ligand-decorated click polypeptide derived nanoparticles for targeted drug delivery applications

A ligand decorated, synthetic polypeptide block copolymer platform with environment-responsive capabilities was designed. We evaluated the potential of this system to function as a polymersome for targeted-delivery of a systemic chemotherapy to tumors. Our system employed click chemistry to provide a pH-responsive polypeptide block that drives nanoparticle assembly, and a ligand (folic acid) conjugated PEG block that targets folate-receptor over-expressing cancer cells. These nanocarriers were found to encapsulate a high loading of conventional chemotherapeutics (e.g. doxorubicin at physiological pH) and release the active therapeutic at lysosomal pH upon cellular uptake. The presence of folic acid on the nanoparticle surface facilitated their active accumulation in folate-receptor-overexpressing cancer cells (KB), compared to untargeted carriers. Folate-targeted nanoparticles loaded with doxorubicin also showed enhanced tumor accumulation in folate-receptor positive KB xenografts, resulting in the suppression of tumor growth in an in vivo hind flank xenograft mouse model.

A Targeted Nanoprobe Based on Carbon Nanotubes-Natural Biopolymer Chitosan Composites

A novel targeting theranostic nanoprobe based on single-walled carbon nanotubes (SWCNTs)-natural biopolymer chitosan composites was developed for cancer cell targeting imaging and fluorescence imaging-guided photodynamic therapy. First, chitosan was respectively conjugated with a tumor-homing molecule folic acid, or a photosensitizing drug pyropheophorbide a using a water-soluble carbodiimide coupling chemistry. Chitosan was fluorescently labeled by fluorescein isothiocyanate via the covalently linkage of the isothiocyanate group with the amino group. Second, SWCNTs were sonicated in the functional chitosan aqueous solution for 6 h at room temperature in order to obtain the nanoprobe (PPa/FITC-SWCNT-FA). The as-prepared nanoprobe has been characterized with transmission electron microscope, confocal microscopy, and cell cytotoxicity tests. Chitosan was decorated onto SWCNTs resulting in the water-dispersible PPa/FITC-SWCNT-FA, and can be selectively transported inside folate receptor-positive tumor cell with good targeting imaging. PPa/FITC-SWCNT-FA exhibited low dark toxicity about 7%–13%, and high phototoxicity about 60%–74% against HeLa cells upon a 635 nm laser irradiation, indicating satisfying biocompatibility and antitumor activity. These results suggest the study could offer a feasible alternative to presently available nanoparticle-based theranostic agents.

Folate-conjugated dually responsive micelles for targeted anticancer drug delivery

Folate-conjugated dual-responsive micelles were developed, sustained and sensitive drug release from the drug loaded micelles was observed. Folate-targeted micelles showed higher anticancer activity and enhanced cellar uptake than non-targeted ones.

Targeted polymer-drug conjugates: Current progress and future perspective

The combination of polymer technology and targeted drug delivery may pave the way for more effective yet safer therapeutic options for cancer therapy. Polymer-drug conjugates belonging to polymer therapeutics represent an emerging approach for drug delivery. The development of smart targeted polymer-drug conjugates that can specifically deliver drugs at a sustained rate to tumor cells may substantially improve the therapeutic index of anticancer agents. In this update, we provide an overview of the most important targeting molecules, and systemically summarize the recent advances in the development of tumor-targeted polymer-drug conjugates. Additionally, several promising approaches for the future will also be presented.

Anti-tumor activity of folate targeted biodegradable polymer-paclitaxel conjugate micelles on EMT-6 breast cancer model

BACKGROUND

Paclitaxel (PTX) is a first line chemotherapy drug for breast cancer. There have been few studies reported concerning the therapeutic efficacy of paclitaxel-conjugated polymeric micelles in breast cancer in vivo.

METHODS

Two kinds of PTX conjugate micelles, one of which (M(PTX)) contained 25 wt.% of PTX and the other (M(FA/PTX)) contained 22.5 wt.% of PTX and 1.4 wt.% of folate (FA), were prepared for cell apoptosis and anti-tumor activity evaluation on EMT-6 mice breast cancer models in comparison with 0.9 wt.% saline (control) and equivalent PTX. Cell apoptosis was analyzed by flow cytometry. Breast tumors were examined histologically with H&E staining and immunohistochemically by examining Bax and Bcl-2 expression. The survival status of tumor-bearing mice with different treatments was also examined.

RESULTS

On day 5 of the drug administration, the average tumor masses were 0.49, 0.33, 0.22, and 0.18 g for the control, PTX, M(PTX) and M(FA/PTX) groups, respectively. The inhibition rates of tumor growth calculated for the three drug groups were 32.6%, 51.6% and 62.3%, respectively. The percentage of cell apoptosis based on flow cytometry was 1.0%, 36.6%, 55.9% and 66.1%, respectively, which showed statistically significant differences (p<0.05) between three drug groups and the control group. Bcl-2 expression of PTX and M(FA/PTX) groups was lower than control group (p<0.05). Bax expression of drug groups was higher than control group (p<0.05). At an equivalent paclitaxel dose of 26.7 mg/kg, the average survival time was 33 days, 31 days, 34 days and 42 days, respectively (p<0.05).

CONCLUSION

The M(FA/PTX) have better anti-tumor activity and are promising in treatment of human breast cancers.

Methotrexate-grafted-oligochitosan micelles as drug carriers: synthesis and biological evaluations

The novel amphiphilic derivatives of Methotrexate-chitosan oligosaccharide (MTX-CHO) with different molar feeding ratios of MTX were synthesized. The degree of MTX substitution ranged from 4.47 to 13.5%. MTX-CHO copolymer formed micelles with an average size of 134.6±14.52 to 236.6±30.01 nm, and zeta potential of 20±5 to 16.8±7.74 mV. The critical micelle concentration was found to range from 125 to 0.56 mg/l. Analysis of micelles with different degree of substitutions (DSs) revealed that the size of micelles decreased by increasing DS while zeta potential was reduced. Release study indicated that drug content had effect on the release rate. With increasing amount of loaded drug in the micelle, release rate was decreased. Drug loaded and unloaded MTX-CHO micelles showed significant cytotoxicity on MDA-MB-231. Loaded micelle was more effective than unloaded one which indicated that conjugation could reduce efficacy of MTX. The viability of MDA-MB-231 in presence of drug loaded micelles was significantly decreased and cell viability at 1 µg/ml was 45.17±9% while the viability of unloaded micelles was 91.86±9.88. These phenomena make MTX-CHO micelles as a good candidate for hydrophobic anticancer drug carrier.

Sonochemical fabrication of dual-targeted redox-responsive smart microcarriers

In the present study, the molecular and magnetic dual-targeted redox-responsive folic acid-cysteine-Fe3O4 microcapsules (FA-Cys-Fe3O4 MCs) have been synthesized via the sonochemical technique, and targeting molecule (folic acid) and Fe3O4 magnetic nanoparticles are introduced into the microcapsule shells successfully. The obtained FA-Cys-Fe3O4 MCs show excellent magnetic responsive ability by the oriented motion under an external magnetic field. The hydrophobic fluorescent dye (Coumarin 6) is successfully loaded into the FA-Cys-Fe3O4 MCs, demonstrating that it could be also easily realized to encapsulate hydrophobic drugs into the FA-Cys-Fe3O4 MCs when the drugs are dispersed into the oil phase before sonication. Cellular uptake demonstrates that FA-Cys-Fe3O4 MCs could target selectively the cells via folate-receptor-mediated endocytosis. Moreover, the FA-Cys-Fe3O4 MCs show their potential ability to be an attractive carrier for drug controlled release owing to the redox responsiveness of the disulfide in the microcapsule shells.

Polyethylene glycol conjugated polymeric nanocapsules for targeted delivery of quercetin to folate-expressing cancer cells in vitro and in vivo

In this work we describe the formulation and characterization of chemically modified polymeric nanocapsules incorporating the anticancer drug, quercetin, for the passive and active targeting to tumors. Folic acid was conjugated to poly(lactide-co-glycolide) (PLGA) polymer to facilitate active targeting to cancer cells. Two different methods for the conjugation of PLGA to folic acid were employed utilizing polyethylene glycol (PEG) as a spacer. Characterization of the conjugates was performed using FTIR and (1)H NMR studies. The PEG and folic acid content was independent of the conjugation methodology employed. PEGylation has shown to reduce the size of the nanocapsule; moreover, zeta-potential was shown to be polymer-type dependent. Comparative studies on the cytotoxicity and cellular uptake of the different formulations by HeLa cells, in the presence and absence of excess folic acid, were carried out using MTT assay and Confocal Laser Scanning Microscopy, respectively. Both results confirmed the selective uptake and cytotoxicity of the folic acid targeted nanocapsules to the folate enriched cancer cells in a folate-dependent manner. Finally, the passive tumor accumulation and the active targeting of the nanocapsules to folate-expressing cells were confirmed upon intravenous administration in HeLa or IGROV-1 tumor-bearing mice. The developed nanocapsules provide a system for targeted delivery of a range of hydrophobic anticancer drugs in vivo.

Bright far-red/near-infrared conjugated polymer nanoparticles for in vivo bioimaging

A highly emissive far-red/near-infrared (FR/NIR) fluorescent conjugated polymer (CP), poly[(9,9-dihexylfluorene)-co-2,1,3-benzothiadiazole-co-4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole] (PFBTDBT10) is designed and synthesized via Suzuki polymerization. Formulation of PFBTDBT10 using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG2000 ) and DSPE-PEG5000-folate as the encapsulation matrix yielded CP-loaded DSPE-PEG-folic acid nanoparticles (CPDP-FA NPs) with bright FR/NIR fluorescence (27% quantum yield) and a large Stoke's shift of 233 nm in aqueous solution. CPDP-FA NPs show improved thermal/photostabilities and larger Stoke's shifts as compared to commercially available quantum dots (Qdot 655) and organic dyes such as Alexa Fluor 555 and Rhodamine 6G. In vivo studies of CPDP-FA NPs on a hepatoma H22 tumor-bearing mouse model reveal that they could serve as an efficient FR/NIR fluorescent probe for targeted in vivo fluorescence imaging and cancer detection in a high contrast and specific manner. Together with the negligible in vivo toxicity, CPDP-FA NPs are promising FR/NIR fluorescent probes for future in vivo applications.

Polymeric micelles for multidrug delivery and combination therapy

The use of conventional therapy based on a single therapeutic agent is not optimal to treat human diseases. The concept called "combination therapy", based on simultaneous administration of multiple therapeutics is recognized as a more efficient solution. Interestingly, this concept has been in use since ancient times in traditional herbal remedies with drug combinations, despite mechanisms of these therapeutics not fully comprehended by scientists. This idea has been recently re-enacted in modern scenarios with the introduction of polymeric micelles loaded with several drugs as multidrug nanocarriers. This Concept article presents current research and developments on the application of polymeric micelles for multidrug delivery and combination therapy. The principles of micelle formation, their structure, and the developments and concept of multidrug delivery are introduced, followed by discussion on recent advances of multidrug delivery concepts directed towards targeted drug delivery and cancer, gene, and RNA therapies. The advantages of various polymeric micelles designed for different applications, and new developments combined with diagnostics and imaging are elucidated. A compilation work from our group based on multidrug-loaded micelles as carriers in drug-releasing implants for local delivery systems based on titania nanotubes is summarized. Finally, an overview of recent developments and prospective outlook for future trends in this field is given.

The effect of N/P ratio on the in vitro and in vivo interaction properties of PEGylated poly[2-(dimethylamino)ethyl methacrylate]-based siRNA complexes

PEG-PnBA-PDMAEMA triblock and PEG-PDMAEMA diblock copolymers are used as model systems for studying the role of N/P ratio on the in vivo behavior of PEGylated siRNA carriers in mice. The presence of a free/uncomplexed polymer population coexisting with siRNA complexes is established. A change in the N/P ratio exerts no significant influence on the in vivo biodistribution and ex vivo blood chemistry properties of the respective systems. Histological analysis of major organs indicates that the presence of uncomplexed polymer elicits toxicity to the organ that is associated with the clearance of the siRNA complexes from the circulation system. This effect can be eliminated by working at N/P ratios near the charge-neutralization point of the complexes.

Lipid-PEG-folate encapsulated nanoparticles with aggregation induced emission characteristics: cellular uptake mechanism and two-photon fluorescence imaging

Folate functionalized nanoparticles (NPs) that contain fluorogens with aggregation-induced emission (AIE) characteristics are fabricated to show bright far-red/near-infrared fluorescence, a large two-photon absorption cross section and low cytotoxicity, which are internalized into MCF-7 cancer cells mainly through caveolae-mediated endocytosis. One-photon excited in vivo fluorescence imaging illustrates that these AIE NPs can accumulate in a tumor and two-photon excited ex vivo tumor tissue imaging reveals that they can be easily detected in the tumor mass at a depth of 400 μm. These studies indicate that AIE NPs are promising alternatives to conventional TPA probes for biological imaging.

Hydrotropic polymeric mixed micelles based on functional hyperbranched polyglycerol copolymers as hepatoma-targeting drug delivery system

Mixed copolymer nanoparticles (NPs) self-assembled from β-cyclodextrin-grafted hyperbranched polyglycerol (HPG-g-CD) and lactobionic acid (LA)-grafted hyperbranched polyglycerol (HPG-g-LA) were applied as carriers for a hydrophobic antitumor drug, paclitaxel (PTX), achieving hepatocellular carcinoma-targeted delivery. The resulting NPs exhibited high drug loading capacity and substantial stability in aqueous solution. In vitro drug release studies demonstrated a controlled drug release profile with increased release at acidic pH. Remarkably, tumor proliferation assays showed that PTX-loaded mixed copolymer NPs inhibited asialoglycoprotein (ASGP) receptor positive HepG2 cell proliferation in a concentration-dependent manner in comparison with ASGP receptor negative BGC-823 cells. Moreover, the competition assay demonstrated that the small molecular LA inhibited the cellular uptake of the PTX-loaded mixed copolymer NPs, indicating the ASGP receptor-mediated endocytosis in HepG2 cells. In addition, the intracellular uptake tests by confocal laser scanning microscopy showed that the mixed copolymer NPs were more efficiently taken up by HepG2 cells compared with HPG-g-CD NPs. These results suggest a feasible application of the mixed copolymer NPs as nanocarriers for hepatoma-targeted delivery of potent antitumor drugs.

Functional coating of liposomes using a folate- polymer conjugate to target folate receptors

Folate-polymer-coated liposomes were developed for targeted chemotherapy using doxorubicin (DXR) as a model drug. Folate-poly(L-lysine) (F–PLL) conjugates with a folate modification degree of 16.7 mol% on epsilon amino groups of PLL were synthesized. DXR-loaded anionic liposomes were coated with F–PLL, and the cellular association of F–PLL-coated liposomes was evaluated by flow cytometry, and confocal microscopy in human nasopharyngeal carcinoma KB cells overexpressing folate receptors (FRs), and human lung adenocarcinoma A549 cells [FR (−)]. The existence of a polymer layer on the surface of F–PLL-coated liposomes was confirmed by zeta potential analysis. The KB cellular association of F–PLL-coated liposomal DXR was increased compared with that of PLL-coated liposomes and was inhibited in the presence of free folic acid. Twofold higher cytotoxicity of F–PLL-coated liposomal DXR was observed compared with that of the PLL-coated liposomal DXR in KB cells, but not in A549 cells, suggesting the presence of FR-mediated endocytosis. These results indicated that folate-targeted liposomes were prepared successfully by coating the folate–polymer conjugate F–PLL. This novel preparation method of folate-targeted liposomes is expected to provide a powerful tool for the development of a folate-targeting drug nanodevice as coating with ligand–polymer conjugates can be applicable to many kinds of particles, as well as to lipid-based particles.

Antitumor activity of folate-targeted, paclitaxel-loaded polymeric micelles on a human esophageal EC9706 cancer cell line

Background

Esophageal cancer is recognized as one of the most refractory pernicious diseases. In addition, it is an aggressive malignancy with a propensity for local progression and distant dissemination. Because of the poor long-term prognosis for patients with esophageal cancer, increasing attention has focused on the integration of targeted agents into current therapeutics. Nevertheless, there have been few studies reported concerning the therapeutic efficacy of paclitaxel-conjugated polymeric micelles in human esophageal cancer in vivo. Therefore, the aim of this research was to investigate the tumor inhibition effect of composite micelles containing folic acid and paclitaxel on the human esophageal EC9706 cancer cell line.

Methods and results

Intravenous administration of folate-targeted, paclitaxel-loaded micelles was demonstrated to be more efficient in inhibiting subcutaneous xenograft tumors and extending the survival rate of tumor-bearing nude mice than free paclitaxel and plain paclitaxel micelles at an equivalent paclitaxel dose of 20 mg/kg, which was further backed up by flow cytometry, TUNEL, and expression of apoptosis-related proteins, including Bax, Bcl2, and caspase 3 in this study.

Conclusion

The folate-mediated paclitaxel-loaded polymeric micelle is a promising agent for the treatment of human esophageal cancer.

Transferrin-conjugated micelles: enhanced accumulation and antitumor effect for transferrin-receptor-overexpressing cancer models

As the transport protein for iron, transferrin can trigger cellular endocytosis once binding to its receptor (TfR) on the cell membrane. Using this property, we conjugated transferrin onto the surface of biodegradable polymeric micelles constructed from amphiphilic block copolymers. The core of micelle was either labeled with a near-infrared dye (NIR) or conjugated with a chemotherapeutic drug paclitaxel (PTX) to study the biodistribution or antitumor effect in nude mice bearing subcutaneous TfR-overexpressing cancers. DLS and TEM showed that the sizes of Tf-conjugated and Tf-free micelles were in the range of 85-110 nm. Confocal laser scanning microscopy and flow cytometry experiments indicated that the uptake efficiency of the micelles by the TfR-overexpressing cells was enhanced by Tf conjugation. Semiquantitative analysis of the NIR signals collected from the tumor site showed that the maximum accumulation was achieved at 28 h in the M(NIR) group, while at 22 h in Tf-M(NIR) groups; and the area under the intensity curve in the Tf-M(NIR) groups was more than that in M(NIR) group. Finally, the tumor inhibition effects of targeting micelles were studied with the gastric carcinoma model which overexpressed TfR. The analysis of tumor volumes and the observation of H&E-stained tumor sections showed that Tf-M(PTX) had the best antitumor effect compared with the control groups (saline, PTX, and M(PTX)). The results of this study demonstrated the potential application of Tf-conjugated polymeric micelles in the treatment of TfR-overexpressing cancers.

Single-particle tracking as a quantitative microscopy-based approach to unravel cell entry mechanisms of viruses and pharmaceutical nanoparticles

Highly sensitive fluorescence microscopy techniques allow single nanoparticles to be tracked during their uptake into living cells with high temporal and spatial resolution. From analysis of the trajectories, random motion can be discriminated from active transport and the average transport velocity and/or diffusion coefficient determined. Such an analysis provides important information regarding the uptake pathway and location of viruses and nanoparticles. In this review, we give an introduction into single-particle tracking (SPT) and determination of the mean-squared displacement. We also give an overview of recent advances in SPT. These include millisecond alternating-laser excitation for removal of spectral crosstalk, alternating wide-field (WF), and total internal reflection fluorescence (TIRF) microscopy for sensitive experiments at the plasma membrane and three-dimensional tracking strategies. Throughout the review, we highlight recent advances regarding the entry (and egress) of natural and artificial viruses obtained via SPT.

Influence of nano-carrier architecture on in vitro siRNA delivery performance and in vivo biodistribution: polyplexes vs micelleplexes

Micelle-based siRNA carriers ("micelleplexes") were prepared from the A-B-C triblock copolymer poly(ethylene glycol)-poly(n-butyl acrylate)-poly(2-(dimethylamino)ethyl methacrylate) (PEG-PnBA-PDMAEMA), and their in vitro performance and in vivo biodistribution properties were compared with the benchmark PEGylated and basic polycation systems PEG-PDMAEMA and PDMAEMA, respectively. The micelle architecture, incorporating increased PEG shielding and a larger particle size (∼50 nm) than polycation-based complexes (polyplexes; ∼10 nm), enhances siRNA delivery performance in two important aspects: in vitro gene silencing efficiency and in vivo tumor accumulation. The in vitro gene silencing efficiency of the micelleplexes (24% in HeLa cells) was significantly better than the statistically insignificant levels observed for PDMAEMA and PEG-PDMAEMA polyplexes under identical conditions. This enhancement is linked to the different mechanisms by which micelleplexes are internalized (i.e., caveolar, etc.) compared to PDMAEMA and PEG-PDMAEMA polyplexes. Folate-functionalization significantly improved micelleplex uptake but had negligible influence on gene-silencing efficiency, suggesting that this parameter is not limited by cellular internalization. In vivo biodistribution analysis revealed that siRNA delivered by micelleplexes was more effectively accumulated and retained in tumor tissues than that delivered by PEGylated polyplexes. Overall, the micelle particle size and architecture appear to improve in vitro and in vivo delivery characteristics without significantly changing other properties, such as cytotoxicity and resistance to enzymes and dissociation. The self-assembled nature of micelleplexes is expected to enable incorporation of imaging modalities inside the hydrophobic micelle core, thus combining therapeutic and diagnostic capabilities. The findings from the present study suggest that the micelleplex-type carrier architecture is a useful platform for potential theranostic and tumor-targeting applications.

Preparation and characterization of thermosensitive pluronic F127-b-poly(ɛ-caprolactone) mixed micelles

The mixed micelles composed of pluronic F127-b-poly(ɛ-caprolactone) (F127-CL) and bovine serum albumin (BSA) or polylactic acid (PLA) were fabricated for application as promising drug carriers. F127-CL copolymers were characterized by (1)H NMR, FT-IR, GPC, DSC, XRD and POM. They can self-assemble into micelles in water by solvent evaporation method. The thermo-responsivities of the pure and mixed micelles were investigated. The drug release behaviors were investigated in phosphate-buffered solution (PBS) and acetate buffer solution (ABS), respectively, at 37°C. The hemolysis and coagulation assay and the tumor cell growth inhibition assays were further evaluated. The morphologies of pure micelles underwent from the coexistence of the rods and spheres to the spheres with increasing the lengths of CL. The micelle behaviors were influenced with the addition of BSA and PLA. Both pure and mixed micelles of F127-CL with CL length of 200 show thermo-responsivities from 25 to 45°C, while form larger aggregations at high temperature. The hemolysis and coagulation assays showed that the micelles possess good blood compatibility. The cytotoxicity results showed that the copolymer was a safe carrier and the encapsulated doxorubicind.HCl remained its potent anti-tumor effect. The in vitro release profiles displayed a sustained release of DOX.HCl from the micelles. The block copolymers can be great potential as a nanocontainer in drug delivery systems.

Self-assembly strategy for the preparation of polymer-based nanoparticles for drug and gene delivery

Nanoparticulate drug-delivery systems have attained much importance because of their injectable property, the possibility to achieve passive targeting and active targeting, and unique advantages to realize stimuli tailored delivery. Molecular self-assembly is a powerful method for fabricating polymer-based nanoparticles, which involves various driving forces, such as hydrophobic interactions, electrostatic interactions, stereocomplexation, host/guest interactions and hydrogen bonding. By fine tuning one or many types of these interactions, self-assemblies with a wide range of structures and functions could be fabricated. In this article, recent developments in different self-assembly strategies for the preparation of polymer-based nanoparticulate delivery systems are discussed.

Visualizing uptake and intracellular trafficking of gene carriers by single-particle tracking

Single-particle microscopy und live-cell single-particle tracking are powerful tools to follow the cellular internalization pathway of individual nanoparticles such as viruses and gene carriers and investigate their interaction with living cells. Those single-cell and single-particle methods can elucidate the "black box" between application of the gene carrier to the cell and the final gene expression and allow the essential bottlenecks to be identified in great detail on the cellular level. In this review we will give a short introduction into single-particle tracking microscopy and present an overview of the mechanisms of DNA delivery from attachment to the cell membrane over internalization towards nuclear entry unraveled by single-particle methods.