Trastuzumab-functionalized nanoparticles of biodegradable copolymers for targeted delivery of docetaxel

Distinguishing the Cellular Transport of Folic Acid Conjugated Nano-Drugs among Different Cell Lines by Using Force Tracing Technique

Folic acid (FA) is a ligand that has been renowned for its strong binding to FA receptor (FR), and the robustness of the specific interaction has led to the generation of multitudinous tumor-targeted nano-drug delivery systems. However, selecting the appropriate FA targeted nano-drugs according to types of cancerous cells to achieve a high effect is critical. Understanding of how the drug is transported through the cell membrane and is delivered intracellularly is very important in screening ideal targeted nano-drugs for cancerous changes in different organs. Herein, by using a force tracing technique based on atomic force microscopy (AFM), the dynamic process of FA-polyamidoamine-Doxorubicin (FA-PAMAM-DOX) entry into different tumor cells (HeLa and A549) and normal cells (Vero) was monitored in real time. The cell membrane transport efficacy of FA-PAMAM-DOX in tumor cells with an FR high overexpression level (HeLa) and FR low overexpression level (A549) is analyzed, which is significantly higher than that in normal cells (Vero), especially for HeLa cells. Subsequently, the intracellular delivery efficiency of FA-PAMAM-DOX in different cell lines was measured by using fluorescence imaging and AFM-based nanoindentation techniques. This report will help to discover the cellular transport mechanism of nano-drugs and screen out optimal therapeutic nano-drugs for different types of tumors.

Dynamics of delivering aptamer targeted nano-drugs into cells

A targeted nano-drug delivery system has provided great potential and benefits to the diagnosis and therapy of cancers. Cell entry is a critical step for taking effect of the targeted nano-drug. In this report, the dynamics of delivering a single aptamer targeted polyamindoamine-camptothecin-AS1411 (PAMAM-CPT-AS1411) nano-drug into cells was investigated using a force tracing technique based on atomic force microscopy. The results show that the specific interaction of AS1411 and nucleolin, which is overexpressed on cancer cells, enhances the efficiency of the PAMAM-CPT-AS1411 cell entry. Moreover, the specific interaction induced receptor-mediated endocytosis prolongs the duration and decreases the speed of a single PAMAM-CPT-AS1411 cell entry, which is helpful to understand the targeted nano-drugs prolonging the therapeutic drug level. However, the required force for PAMAM-CPT-AS1411 cell entry is not changed. This report will provide a novel and potential method for achieving the precise dynamics of targeted nano-drug delivery.

An Overview of Antibody Conjugated Polymeric Nanoparticles for Breast Cancer Therapy

Nanoparticles (NPs) are promising drug delivery systems (DDS) for identifying and treating cancer. Active targeting NPs can be generated by conjugation with ligands that bind overexpressed or mutant cell surface receptors on target cells that are poorly or not even expressed on normal cells. Receptor-mediated endocytosis of the NPs occurs and the drug is released inside the cell or in the surrounding tissue due to the bystander effect. Antibodies are the most frequently used ligands to actively target tumor cells. In this context, antibody-based therapies have been extensively used in HER2+ breast cancer. However, some patients inherently display resistance and in advanced stages, almost all eventually progress. Functionalized NPs through conjugation with antibodies appear to be a promising strategy to optimize targeted therapies due to properties related to biocompatibility, suitable delivery control and efficiency of functionalization. This review is focused on the different strategies to conjugate antibodies into polymeric NPs. Recent antibody conjugation approaches applied to the improvement of breast cancer therapy are highlighted in this review.

Acidity/Reducibility Dual-Responsive Hollow Mesoporous Organosilica Nanoplatforms for Tumor-Specific Self-Assembly and Synergistic Therapy

Featured with a large surface area, uniform interpenetrating mesopores, diverse organic framework hybridization, and well-defined surface properties, the hollow mesoporous organosilica nanoparticle (HMON) represents a promising paradigm in drug delivery systems with excellent biocompatibility. However, effective tumor accumulation and precise cancer theranostics of the HMON still remain a challenge. In this study, an "ammonia-assisted hot water etching" method is applied for the successful construction of sub-50 nm thioether/phenylene dual-hybridized HMON with low hemolytic effect. Particularly, the surface modification with Mo(VI)-based polyoxometalate (POM) clusters drives the self-assembly of HMON in the mild acidic tumor microenvironment (TME) to achieve enhanced tumor retention and accumulation. More importantly, the reducibility-activated Mo(VI)-to-Mo(V) conversion within POM not only endows the POM-anchored HMON with outstanding TME-responsive photoacoustic (PA) imaging contrast and photothermal therapy (PTT) performance but also plays an indispensable role in controllably triggering the decomposition of the Mn2(CO)10 payload for CO release, which gives rise to remarkable synergistic PTT-enhanced CO gas therapy for complete tumor eradication. By harnessing the unique acidic and redox properties of TME, the judiciously designed smart POM-anchored HMON nanoplatform is expected to act as a "magic bomb" to selectively destroy cancer without damaging normal tissues. This nanoplatform holds significant potential in realizing TME-responsive self-assembly for enhanced tumor accumulation and precise tumor-specific synergistic therapy, which is very promising for clinical translation.

Layer-by-layer assembly of graphene oxide on thermosensitive liposomes for photo-chemotherapy

Stimuli responsive polyelectrolyte nanoparticles have been developed for chemo-photothermal destruction of breast cancer cells. This novel system, called layer by layer Lipo-graph (LBL Lipo-graph), is composed of alternate layers of graphene oxide (GO) and graphene oxide conjugated poly (l-lysine) (GO-PLL) deposited on cationic liposomes encapsulating doxorubicin. Various concentrations of GO and GO-PLL were examined and the optimal LBL Lipo-graph was found to have a particle size of 267.9 ± 13 nm, zeta potential of +43.9 ± 6.9 mV and encapsulation efficiency of 86.4 ± 4.7%. The morphology of LBL Lipo-graph was examined by cryogenic-transmission electron microscopy (Cryo-TEM), atomic force microcopy (AFM) and scanning electron microscopy (SEM). The buildup of LBL Lipo-graph was confirmed via ultraviolet-visible (UV-Vis) spectrophotometry, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. Infra-red (IR) response suggests that four layers are sufficient to induce a gel-to-liquid phase transition in response to near infra-red (NIR) laser irradiation. Light-matter interaction of LBL Lipo-graph was studied by calculating the absorption cross section in the frequency domain by utilizing Fourier analysis. Drug release assay indicates that the LBL Lipo-graph releases much faster in an acidic environment than a liposome control. A cytotoxicity assay was conducted to prove the efficacy of LBL Lipo-graph to destroy MD-MB-231 cells in response to NIR laser emission. Also, image stream flow cytometry and two photon microcopy provide supportive data for the potential application of LBL Lipo-graph for photothermal therapy. Study results suggest the novel dual-sensitive nanoparticles allow intracellular doxorubin delivery and respond to either acidic environments or NIR excitation.

STATEMENT OF SIGNIFICANCE

Stimuli sensitive hybrid nanoparticles have been synthesized using a layer-by-layer technique and demonstrated for dual chemo-photothermal destruction of breast cancer cells. The hybrid nanoparticles are composed of alternating layers of graphene oxide and graphene oxide conjugated poly-l-lysine coating the surface of a thermosensitive cationic liposome containing doxorubicin as a core. Data suggests that the hybrid nanoparticles may offer many advantages for chemo-photothermal therapy. Advantages include a decrease of the initial burst release which may result in the reduction in systemic toxicity, increase in pH responsivity around the tumor environment and improved NIR light absorption.

Magnetic nanobubbles with potential for targeted drug delivery and trimodal imaging in breast cancer: an in vitro study

Aim: The aim of this study was to improve tumor-targeted therapy for breast cancer by designing magnetic nanobubbles with the potential for targeted drug delivery and multimodal imaging. Materials & methods: Herceptin-decorated and ultrasmall superparamagnetic iron oxide (USPIO)/paclitaxel (PTX)-embedded nanobubbles (PTX-USPIO-HER-NBs) were manufactured by combining a modified double-emulsion evaporation process with carbodiimide technique. PTX-USPIO-HER-NBs were examined for characterization, specific cell-targeting ability and multimodal imaging. Results: PTX-USPIO-HER-NBs exhibited excellent entrapment efficiency of Herceptin/PTX/USPIO and showed greater cytotoxic effects than other delivery platforms. Low-frequency ultrasound triggered accelerated PTX release. Moreover, the magnetic nanobubbles were able to enhance ultrasound, magnetic resonance and photoacoustics trimodal imaging. Conclusion: These results suggest that PTX-USPIO-HER-NBs have potential as a multimodal contrast agent and as a system for ultrasound-triggered drug release in breast cancer.

The effect of dual-functional hyaluronic acid-vitamin E succinate micelles on targeting delivery of doxorubicin

Tumor-targeted delivery system has been developed as an attractive strategy for effective tumor therapy. In this study, in order to enhance the antitumor effects of doxorubicin (DOX), amphiphilic hyaluronic acid (HA)-conjugated vitamin E succinate (VES) copolymers (HA-VES) with different degrees of substitution (DS) were prepared with synergistic antitumor effects and active targeting activities, and utilized as nanocarriers for the efficient delivery of DOX. DOX-loaded HA-VES polymeric micelles (HA-VES/DOX) self-assembled from dual-functional HA-VES copolymer and exhibited excellent loading efficiency and superior colloidal stability. In vitro, HA-VES/DOX displayed enhanced cytotoxicity with synergistic anticancer effects of HA-VES copolymer, high apoptosis-inducing activities of tumor cells, and reversal effects of DOX on multidrug resistance, in comparison with DOX. Also, in vitro cellular uptake and subcellular localization studies revealed that HA-VES/DOX could more efficiently internalize into cancer cells and selectively release DOX within lysosomes, thereby enhancing the distribution of DOX in nuclei and facilitating its interactions with DNA. Specifically, HA-VES/DOX decreased the activity of CD44 mRNA and improved the targeting efficiency on MCF-7 cells, based on the active recognition between HA and CD44 receptor. More importantly, HA-VES/DOX displayed better tumor accumulation and targeting, and enhanced antitumor efficacy with reduced systemic toxicity in 4T1 tumor-bearing mice. In summary, the developed HA-VES-based drug delivery system, which increased drug targeting on the tumor site and exhibited preferable anticancer activity, could hold great potential as an effective and promising strategy for efficient tumor therapy.

On The Latest Three-Stage Development of Nanomedicines based on Upconversion Nanoparticles

Following the "detect-to-treat" strategy, by biological engineering, the emerging upconversion nanoparticles (UCNPs) have become one of the most promising inorganic nanomedicines, and their biomedical applications have gradually shifted from multimodal tumor imaging to highly efficient cancer therapy. The past few years have witnessed a three-stage development of UCNP-based nanomedicines. On one hand, UCNPs can optimize each clinical treatment tool (chemotherapy, photodynamic therapy (PDT), radiotherapy (RT)) by controlled drug delivery/release, near-infrared (NIR)-excited deep PDT, and radiosensitization, respectively, all of which contribute greatly to the optimized treatment efficacy along with minimized side effects. On the other hand, several individual treatments can be "smartly" integrated into a single UCNP-based nanotheranostic system for multimodal synergetic therapy, which can further improve the overall therapeutic effectiveness. Especially, UCNPs provide more-effective strategies for overcoming tumor hypoxia, thus leading to an ideal treatment efficacy for complete eradication of solid tumors. Finally, the critical issues regarding the future development of UCNPs are discussed to promote the clinic-translational applications of UCNP-based nanomedicines, as well as realization of our "one drug fits all" dream.

Co-delivery of chemotherapeutics and proteins for synergistic therapy

Combination therapy with chemotherapeutics and protein therapeutics, typically cytokines and antibodies, has been a type of crucial approaches for synergistic cancer treatment. However, conventional approaches by simultaneous administration of free chemotherapeutic drugs and proteins lead to limitations for further optimizing the synergistic effects, due to the distinct in vivo pharmacokinetics and distribution of small drugs and proteins, insufficient tumor selectivity and tumor accumulation, unpredictable drug/protein ratios at tumor sites, short half-lives, and serious systemic adverse effects. Consequently, to obtain optimal synergistic anti-tumor efficacy, considerable efforts have been devoted to develop the co-delivery systems for co-incorporating chemotherapeutics and proteins into a single carrier system and subsequently releasing the dual or multiple payloads at desired target sites in a more controllable manner. The co-delivery systems result in markedly enhanced blood stability and in vivo half-lives of the small drugs and proteins, elevated tumor accumulation, as well as the capability of delivering the multiple agents to the same target sites with rational drug/protein ratios, which may facilitate maximizing the synergistic effects and therefore lead to optimal antitumor efficacy. This review emphasizes the recent advances in the co-delivery systems for chemotherapeutics and proteins, typically cytokines and antibodies, for systemic or localized synergistic cancer treatment. Moreover, the proposed mechanisms responsible for the synergy of chemotherapeutic drugs and proteins are discussed.

Targeting docetaxel-PLA nanoparticles simultaneously inhibit tumor growth and liver metastases of small cell lung cancer

Small cell lung cancer (SCLC) is one of the most malignant cancers in the world and 5-year survival rate has not been significantly improved with conventional chemotherapy. Targeting treatment may be a promising alternative to enhance the antitumor efficacy. Present study was aimed at establishing a targeting nanodrug delivery system for SCLC therapy. A targeting peptide (AHSGMYP, named AP), screened in H446 cells by phage display technology, was conjugated to the docetaxel (DTX) encapsulated polylactic acid nanoparticles (DN) to prepare the targeting DTX nanoparticles (AP-DN). Cell cytotoxicity, cellular uptake, therapeutic efficacy and biodistribution of AP-DN were investigated in vitro and in vivo experiment. The mean particle size of AP-DN was 260 nm with encapsulation efficiency >94% and a sustained release profile. Cytotoxicity of AP-DN against H446 cell was superior to that of DTX and DN. AP-DN exhibited excellent antitumor efficacy and particularly effectively inhibited the liver metastases with better tolerance. Results of cellular uptake and biodistribution indicated that the excellent antitumor efficacy of AP-DN was attributed to both the increased accumulation of drug and cellular uptake. To our knowledge, this is the first report on establishing SCLC targeting delivery system which offers a potential therapeutic alterative for SCLC therapy.

Vitamin E-based nanomedicines for anti-cancer drug delivery

This review aims to highlight the development of novel vitamin E conjugates for the vectorization of active pharmaceutical ingredients through nanotechnologies. The physico-chemical and biological properties of vitamin E derivatives offer multiple advantages in drug delivery like biocompatibility, improvement of drug solubility and anticancer activity. Nanomedicines have shown high potential in drug delivery since (i) they may offer better drug biopharmaceutical properties such as longer half-life or better bioavailability and (ii) they have shown benefits in cancer therapy by improving anticancer drug therapeutic index. Vitamin E-based nanomedicines were developed to combine the pharmaceutical properties of both vitamin E and nanomedicines for two purposes: (i) to improve water solubility of hydrophobic drugs and (ii) to enhance the therapeutic efficiency of anticancer agents. This review is divided into three parts: the first one describes the biology and the metabolic functions of vitamin E, the second one focuses on the anticancer activity of two vitamin E derivatives: vitamin E succinate (TOS) and vitamin E polyethylene glycol-succinate (TPGS). Finally, in the third part, we discuss vitamin E derivatives based-nanomedicines.

Effects of PEG tethering chain length of vitamin E TPGS with a Herceptin-functionalized nanoparticle formulation for targeted delivery of anticancer drugs

Drug formulation by ligand conjugated nanoparticles of biodegradable polymers has become one of the most important strategies in drug targeting. We have developed in our previous work nanoparticles of a mixture of two vitamin E TPGS based copolymers PLA-TPGS and TPGS-TOOH with the latter for Herceptin conjugation for targeted delivery of anticancer drugs such as docetaxel to the cancer cells of human epidermal growth factor receptor 2 (HER2) overexpression. In this research, we investigated the effects of the PEG chain length in TPGS, which is in fact a PEGylated vitamin E, on the cellular uptake and cytotoxicity of the drug formulated in the Herceptin-conjugated nanoparticles of PLA-TPGS/TPGS-COOH blend (NPs). Such NPs of PEG1000, PEG2000, PEG3350 and PEG5000, i.e. the PEG of molecule weight 1000, 2000, 3350 and 5000, were prepared by the nanoprecipitation method and characterized for their size and size distribution, drug loading, surface morphology, surface charge and surface chemistry as well as in vitro drug release profile, cellular uptake and cytotoxicity. We found among such nanoparticles, those of PEG1000, i.e. of the shortest PEG tethering chain length, could result in the best therapeutic effects, which are 24.1%, 37.3%, 38.1% more efficient in cellular uptake and 68.1%, 90%, 92.6% lower in IC50 (thus higher in cytotoxicity) than the Herceptin-conjugated nanoparticles of PLA-TPGS/TPGS-COOH blend of PEG2000, PEG3350 and PEG5000 respectively in treatment of SK-BR-3 cancer cells which are of high HER2 overexpression. We provided a theoretical explanation from surface mechanics and thermodynamics for endocytosis of nanoparticles.

Trastuzumab-conjugated vitamin E TPGS liposomes for sustained and targeted delivery of docetaxel

OBJECTIVES

In this study, the authors developed D-α-tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS or simply TPGS) liposomes and further conjugated them to trastuzumab for controlled and targeted delivery of docetaxel (DTX) as a model hydrophobic drug.

METHODS

DTX- or coumarin-6-loaded liposomes were prepared by solvent injection method and characterized for size and size distribution, surface charge, surface chemistry and drug encapsulation efficiency and drug release profile. SK-BR-3 cells were employed as an in vitro model for HER2-positive breast cancer and assessed for their cellular uptake and cytotoxicity of the two liposomal formulations. In vivo pharmacokinetics (PK) was investigated in Sprague-Dawley rats.

RESULTS

The IC(50) value was found to be 20.23 ± 1.95, 3.74 ± 0.98, 0.08 ± 0.4 μg/ml for the marketed preparation of DTX, TPGS liposomes and trastuzumab-conjugated TPGS liposomes, respectively after 24 h incubation with SK-BR-3 cells. In vivo PK experiments showed that i.v. administration of trastuzumab-conjugated liposomes achieved 1.9 and 10 times longer half-life, respectively than PEG-coated liposomes and DTX. The area under the curve (AUC) was increased by 3.47- and 1.728-fold, respectively.

CONCLUSION

The trastuzumab-conjugated vitamin E TPGS-coated liposomes showed greater potential for sustained and targeted chemotherapy in the treatment of HER2 overexpressing breast cancer.

Multimodality treatment of cancer with herceptin conjugated, thermomagnetic iron oxides and docetaxel loaded nanoparticles of biodegradable polymers

We developed a system of nanoparticles of poly(lactide)-d-α-tocopheryl polyethylene glycol succinate (PLA-TPGS) and carboxyl group-terminated TPGS (TPGS-COOH) copolymer blend for multimodality treatment of cancer, which formulated docetaxel for chemotherapy, herceptin for biotherapy and targeting, and iron oxides (IOs) for hyperthermia therapy, which are denoted as MMNPs. It is demonstrated that the MMNPs achieved a significantly higher therapeutic effects than the various combination of the corresponding individual modality treatment NPs and the dual modality treatment NPs due to the synergistic effects among the chemo, bio, and thermo therapies. We further developed a method by employing the concept of NPs IC50, the concentration of the agent-, or agents-loaded nanoparticles that is needed to kill 50% of the cancer cells, to quantitatively access the synergistic effects of the multimodality treatment. It is shown by employing the SK-BR-3 cell line as an in vitro model of the HER2-positive breast cancer that the NPs IC50 is 0.42 mg/mL DCL-NPs plus 1.33 mg/mL Her-NPs plus 0.59 mg/mL IOs-NPs, a total NPs concentration of 2.34 mg/mL for the treatment of a physical mixture of the DCL-NPs, Her-NPs and IOs-NPs at the 1:2:7 weight ratio, while it is only 0.0011 mg/mL for the MMNPs for 24 h, which is 2130 fold more efficient than the physical mixture of the corresponding single modality treatments.

AS1411 aptamer tagged PLGA-lecithin-PEG nanoparticles for tumor cell targeting and drug delivery

Liposomes and polymers are widely used drug carriers for controlled release since they offer many advantages like increased treatment effectiveness, reduced toxicity and are of biodegradable nature. In this work, anticancer drug-loaded PLGA-lecithin-PEG nanoparticles (NPs) were synthesized and were functionalized with AS1411 anti-nucleolin aptamers for site-specific targeting against tumor cells which over expresses nucleolin receptors. The particles were characterized by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The drug-loading efficiency, encapsulation efficiency and in vitro drug release studies were conducted using UV spectroscopy. Cytotoxicity studies were carried out in two different cancer cell lines, MCF-7 and GI-1 cells and two different normal cells, L929 cells and HMEC cells. Confocal microscopy and flowcytometry confirmed the cellular uptake of particles and targeted drug delivery. The morphology analysis of the NPs proved that the particles were smooth and spherical in shape with a size ranging from 60 to 110 nm. Drug-loading studies indicated that under the same drug loading, the aptamer-targeted NPs show enhanced cancer killing effect compared to the corresponding non-targeted NPs. In addition, the PLGA-lecithin-PEG NPs exhibited high encapsulation efficiency and superior sustained drug release than the drug loaded in plain PLGA NPs. The results confirmed that AS1411 aptamer-PLGA-lecithin-PEG NPs are potential carrier candidates for differential targeted drug delivery.

Quantitative control of targeting effect of anticancer drugs formulated by ligand-conjugated nanoparticles of biodegradable copolymer blend

There have been two strategies developed in the recent literature for quantitative control of the targeting effects for drug delivery by ligand-conjugated nanoparticles of biodegradable copolymer blend such as PLGA/PLGA-PEG, i.e. the pre-conjugation strategy and the post-conjugation strategy, in which the ligand conjugation was made before and after the nanoparticle formulation respectively. This research developed another drug delivery system of the PLA-TPGS/TPGS-COOH copolymer blend and further improved the post-conjugation strategy to precisely control the targeting effects by two ways: one is to adjust the PLA-TPGS:TPGS-COOH copolymer blend ratio in the nanoparticle formulation process, which provides a way for coarse control, and another is to control the feeding concentration of the ligand in the herceptin conjugation process, which further provides a fine control. Herceptin conjugation was visualized by the FETEM with immumogold labeling and further quantified by the two techniques, i.e. the Bradford assay and the flow cytometry to confirm each other. The positive correlation between the surface density of the ligand and the cellular internalization as well as the cytotoxicity of the nanoparticle formulations was assessed, which demonstrated that the strategy developed in this research is simple and feasible, which can precisely control the targeting effects of the nanoparticles of biodegradable polymers as well as other nanocarriers such as micelles and liposomes.

Folate-targeted polymeric nanoparticle formulation of docetaxel is an effective molecularly targeted radiosensitizer with efficacy dependent on the timing of radiotherapy

Nanoparticle (NP) chemotherapeutics hold great potential as radiosensitizers. Their unique properties, such as preferential accumulation in tumors and their ability to target tumors through molecular targeting ligands, are ideally suited for radiosensitization. We aimed to develop a molecularly targeted nanoparticle formulation of docetaxel (Dtxl) and evaluate its property as a radiosensitizer. Using a biodegradable and biocompatible lipid-polymer NP platform and folate as a molecular targeting ligand, we engineered a folate-targeted nanoparticle (FT-NP) formulation of Dtxl. These NPs have sizes of 72 ± 4 nm and surface charges of -42 ± 8 mV. Using folate receptor overexpressing KB cells and folate receptor low HTB-43 cells, we showed folate-mediated intracellular uptake of NPs. In vitro radiosensitization studies initially showed FT-NP is less effective than Dtxl as a radiosensitizer. However, the radiosensitization efficacy is dependent on the timing of radiotherapy. In vitro radiosensitization conducted with irradiation given at the optimal time (24 h) showed FT-NP Dtxl is as effective as Dtxl. When FT-NP Dtxl is compared to Dtxl and nontargeted nanoparticle (NT-NP) Dtxl in vivo, FT-NP was found to be significantly more effective than Dtxl or NT-NP Dtxl as a radiosensitizer. We also confirmed that radiosensitization is dependent on timing of irradiation in vivo. In summary, FT-NP Dtxl is an effective radiosensitizer in folate-receptor overexpressing tumor cells. Time of irradiation is critical in achieving maximal efficacy with this nanoparticle platform. To the best of our knowledge, our report is the first to demonstrate the potential of molecularly targeted NPs as a promising new class of radiosensitizers.

A strategy for precision engineering of nanoparticles of biodegradable copolymers for quantitative control of targeted drug delivery

Research on quantitative control of targeting effect for the drug delivery system of ligand-conjugated nanoparticles of biodegradable polymers is at the cutting edge in the design of drug delivery device. In this work, we developed a post-conjugation strategy, which makes the ligand conjugation after the preparation of the drug-loaded nanoparticles of two copolymers blend. We synthesized the PLGA-PEG copolymer with PEG functioning as the linker molecule needed for herceptin conjugation. Docetaxel-loaded nanoparticles of the PLGA-PEG/PLGA copolymer blend were prepared by the nanoprecipitation method. Anti-HER2 antibody (heceptin), which targets the breast cancer cells of HER2 receptor overexpression, was conjugated on the drug-loaded PLGA-PEG/PLGA nanoparticles for sustained, controlled and targeted delivery of docetaxel. We demonstrated that the targeting effect can be quantitatively controlled by two ways, i.e. (1) adjusting the copolymer blend ratio of the nanoparticle matrix, which showed within the range of 20% PLGA/PEG in the copolymer blend a linear relation with the ligand density on the nanoparticle surface, and (2) adjusting the herceptin feed molar ratio to NH2 in the linker molecules appearing on the nanoparticle surface, which also showed a linear relation. Compared with the pre-conjugation strategy developed recently in the literature, in which the ligand was firstly conjugated onto the PLGA-PEG copolymer before preparation of the nanoparticles of the PLGA-PEG/PLGA copolymer blend, the post-conjugation strategy provides more efficient use of the ligand and protects its bioactivity in the nanoparticle preparation process, thus resulting in much better performance in drug targeting, which was assessed in vitro with SK-BR-3 breast cancer cells of HER2 receptor overexpression and MCF7 breast cancer cells of HER2 receptors moderate expression.