Parallel microfluidic synthesis of size-tunable polymeric nanoparticles using 3D flow focusing towards in vivo study.

Microfluidic synthesis of nanoparticles (NPs) can enhance the controllability and reproducibility in physicochemical properties of NPs compared to bulk synthesis methods. However, applications of microfluidic synthesis are typically limited to in vitro studies due to low production rates. Herein, we report the parallelization of NP synthesis by 3D hydrodynamic flow focusing (HFF) using a multilayer microfluidic system to enhance the production rate without losing the advantages of reproducibility, controllability, and robustness. Using parallel 3D HFF, polymeric poly(lactide-co-glycolide)-b-polyethyleneglycol (PLGA-PEG) NPs with sizes tunable in the range of 13-150 nm could be synthesized reproducibly with high production rate. As a proof of concept, we used this system to perform in vivo pharmacokinetic and biodistribution study of small (20 nm diameter) PLGA-PEG NPs that are otherwise difficult to synthesize. Microfluidic parallelization thus enables synthesis of NPs with tunable properties with production rates suitable for both in vitro and in vivo studies. FROM THE CLINICAL EDITOR: Applications of nanoparticle synthesis with microfluidic methods are typically limited to in vitro studies due to low production rates. The team of authors of this proof-of-principle study reports on the successful parallelization of NP synthesis by 3D hydrodynamic flow focusing using a multilayer microfluidic system to enhance production rate without losing the advantages of reproducibility, controllability, and robustness.

Spontaneous formation of heterogeneous patches on polymer-lipid core-shell particle surfaces during self-assembly.

Spontaneous formation of heterogeneous patches on the surface of lipid-based nanoparticles (NPs) and microparticles (MPs) due to the segregation of two different functional groups. Patch formation is observed when tracing the functional groups with quantum dots, gold nanoparticles, and fluorescent dyes. This discovery could have important implications for the future design of self-assembled NPs and MPs for different biomedical applications.

Engineering of self-assembled nanoparticle platform for precisely controlled combination drug therapy.

The genomic revolution has identified therapeutic targets for a plethora of diseases, creating a need to develop robust technologies for combination drug therapy. In the present work, we describe a self-assembled polymeric nanoparticle (NP) platform to target and control precisely the codelivery of drugs with varying physicochemical properties to cancer cells. As proof of concept, we codelivered cisplatin and docetaxel (Dtxl) to prostate cancer cells with synergistic cytotoxicity. A polylactide (PLA) derivative with pendant hydroxyl groups was prepared and conjugated to a platinum(IV) [Pt(IV)] prodrug, c,t,c-[Pt(NH(3))(2)(O(2)CCH(2)CH(2)COOH)(OH)Cl(2)] [PLA-Pt(IV)]. A blend of PLA-Pt(IV) functionalized polymer and carboxyl-terminated poly(D,L-lactic-co-glycolic acid)-block-poly(ethylene glycol) copolymer in the presence or absence of Dtxl, was converted, in microfluidic channels, to NPs with a diameter of ∼100 nm. This process resulted in excellent encapsulation efficiency (EE) and high loading of both hydrophilic platinum prodrug and hydrophobic Dtxl with reproducible EEs and loadings. The surface of the NPs was derivatized with the A10 aptamer, which binds to the prostate-specific membrane antigen (PSMA) on prostate cancer cells. These NPs undergo controlled release of both drugs over a period of 48-72 h. Targeted NPs were internalized by the PSMA-expressing LNCaP cells via endocytosis, and formation of cisplatin 1,2-d(GpG) intrastrand cross-links on nuclear DNA was verified. In vitro toxicities demonstrated superiority of the targeted dual-drug combination NPs over NPs with single drug or nontargeted NPs. This work reveals the potential of a single, programmable nanoparticle to blend and deliver a combination of drugs for cancer treatment.

Targeted polymeric therapeutic nanoparticles: design, development and clinical translation.

Polymeric materials have been used in a range of pharmaceutical and biotechnology products for more than 40 years. These materials have evolved from their earlier use as biodegradable products such as resorbable sutures, orthopaedic implants, macroscale and microscale drug delivery systems such as microparticles and wafers used as controlled drug release depots, to multifunctional nanoparticles (NPs) capable of targeting, and controlled release of therapeutic and diagnostic agents. These newer generations of targeted and controlled release polymeric NPs are now engineered to navigate the complex in vivo environment, and incorporate functionalities for achieving target specificity, control of drug concentration and exposure kinetics at the tissue, cell, and subcellular levels. Indeed this optimization of drug pharmacology as aided by careful design of multifunctional NPs can lead to improved drug safety and efficacy, and may be complimentary to drug enhancements that are traditionally achieved by medicinal chemistry. In this regard, polymeric NPs have the potential to result in a highly differentiated new class of therapeutics, distinct from the original active drugs used in their composition, and distinct from first generation NPs that largely facilitated drug formulation. A greater flexibility in the design of drug molecules themselves may also be facilitated following their incorporation into NPs, as drug properties (solubility, metabolism, plasma binding, biodistribution, target tissue accumulation) will no longer be constrained to the same extent by drug chemical composition, but also become in-part the function of the physicochemical properties of the NP. The combination of optimally designed drugs with optimally engineered polymeric NPs opens up the possibility of improved clinical outcomes that may not be achievable with the administration of drugs in their conventional form. In this critical review, we aim to provide insights into the design and development of targeted polymeric NPs and to highlight the challenges associated with the engineering of this novel class of therapeutics, including considerations of NP design optimization, development and biophysicochemical properties. Additionally, we highlight some recent examples from the literature, which demonstrate current trends and novel concepts in both the design and utility of targeted polymeric NPs (444 references).

Microfluidic platform for combinatorial synthesis and optimization of targeted nanoparticles for cancer therapy.

Taking a nanoparticle (NP) from discovery to clinical translation has been slow compared to small molecules, in part by the lack of systems that enable their precise engineering and rapid optimization. In this work we have developed a microfluidic platform for the rapid, combinatorial synthesis and optimization of NPs. The system takes in a number of NP precursors from which a library of NPs with varying size, surface charge, target ligand density, and drug load is produced in a reproducible manner. We rapidly synthesized 45 different formulations of poly(lactic-co-glycolic acid)-b-poly(ethylene glycol) NPs of different size and surface composition and screened and ranked the NPs for their ability to evade macrophage uptake in vitro. Comparison of the results to pharmacokinetic studies in vivo in mice revealed a correlation between in vitro screen and in vivo behavior. Next, we selected NP synthesis parameters that resulted in longer blood half-life and used the microfluidic platform to synthesize targeted NPs with varying targeting ligand density (using a model targeting ligand against cancer cells). We screened NPs in vitro against prostate cancer cells as well as macrophages, identifying one formulation that exhibited high uptake by cancer cells yet similar macrophage uptake compared to nontargeted NPs. In vivo, the selected targeted NPs showed a 3.5-fold increase in tumor accumulation in mice compared to nontargeted NPs. The developed microfluidic platform in this work represents a tool that could potentially accelerate the discovery and clinical translation of NPs.

Synergistic cytotoxicity of irinotecan and cisplatin in dual-drug targeted polymeric nanoparticles.

AIM: Two unexplored aspects for irinotecan and cisplatin (I&C) combination chemotherapy are: actively targeting both drugs to a specific diseased cell type, and delivering both drugs on the same vehicle to ensure their synchronized entry into the cell at a well-defined ratio. In this work, the authors report the use of targeted polymeric nanoparticles (NPs) to coencapsulate and deliver I&C to cancer cells expressing the prostate-specific membrane antigen. MATERIALS & METHODS: Targeted NPs were prepared in a single step by mixing four different precursors inside microfluidic devices. RESULTS: I&C were encapsulated in 55-nm NPs and showed an eightfold increase in internalization by prostate-specific membrane antigen-expressing LNCaP cells compared with nontargeted NPs. NPs coencapsulating both drugs exhibited strong synergism in LNCaP cells with a combination index of 0.2. CONCLUSION: The strategy of coencapsulating both I&C in a single NP targeted to a specific cell type could potentially be used to treat different types of cancer.

Microfluidic technologies for accelerating the clinical translation of nanoparticles.

Using nanoparticles for therapy and imaging holds tremendous promise for the treatment of major diseases such as cancer. However, their translation into the clinic has been slow because it remains difficult to produce nanoparticles that are consistent 'batch-to-batch', and in sufficient quantities for clinical research. Moreover, platforms for rapid screening of nanoparticles are still lacking. Recent microfluidic technologies can tackle some of these issues, and offer a way to accelerate the clinical translation of nanoparticles. In this Progress Article, we highlight the advances in microfluidic systems that can synthesize libraries of nanoparticles in a well-controlled, reproducible and high-throughput manner. We also discuss the use of microfluidics for rapidly evaluating nanoparticles in vitro under microenvironments that mimic the in vivo conditions. Furthermore, we highlight some systems that can manipulate small organisms, which could be used for evaluating the in vivo toxicity of nanoparticles or for drug screening. We conclude with a critical assessment of the near- and long-term impact of microfluidics in the field of nanomedicine.

Recent developments in multifunctional hybrid nanoparticles: opportunities and challenges in cancer therapy.

Multifunctional hybrid nanoparticles combine some of the unique physical and chemical characteristics of two or more classes of materials, such as polymers, liposomes, metals, quantum dots and mesoporous silica among others, to create a versatile and robust new class of nanoparticles. Here we discuss the most recent synthetic strategies to create these hybrid systems and analyze four key design aspects: stability, encapsulation of therapeutic and imaging agents, controlled release of encapsulated agents, and biocompatibility. Through the combination of multiple nanomaterials, hybrid nanoparticles aim to expand the functionality of single-component systems, using the strengths of one material to improve on weaknesses of another. We then examine how hybrid nanoparticle platforms provide unique opportunities in cancer therapy, specifically in the treatment of multidrug resistant cancer. Finally, we discuss some of the challenges hybrid nanoparticles systems might face in their large scale synthesis and commercialization in the biopharmaceutical industry.

Effects of ligands with different water solubilities on self-assembly and properties of targeted nanoparticles.

The engineering of drug-encapsulated targeted nanoparticles (NPs) has the potential to revolutionize drug therapy. A major challenge for the smooth translation of targeted NPs to the clinic has been developing methods for the prediction and optimization of the NP surface composition, especially when targeting ligands (TL) of different chemical properties are involved in the NP self-assembly process. Here we investigated the self-assembly and properties of two different targeted NPs decorated with two widely used TLs that have different water solubilities, and developed methods to characterize and optimize NP surface composition. We synthesized two different biofunctional polymers composed of poly(lactide-co-glycolide)-b-polyethyleneglycol-RGD (PLGA-PEG-RGD, high water solubility TL) and PLGA-PEG-Folate (low water solubility TL). Targeted NPs with different ligand densities were prepared by mixing TL-conjugated polymers with non-conjugated PLGA-PEG at different ratios through nanoprecipitation. The NP surface composition was quantified and the results revealed two distinct nanoparticle assembly behaviors: for the case of PLGA-PEG-RGD, nearly all RGD molecules conjugated to the polymer were found to be on the surface of the NPs. In contrast, only ∼20% of the folate from PLGA-PEG-Folate was present on the NP surface while the rest remained presumably buried in the PLGA NP core due to hydrophobic interactions of PLGA and folate. Finally, in vitro phagocytosis and cell targeting of NPs were investigated, from which a window of NP formulations exhibiting minimum uptake by macrophages and maximum uptake by targeted cells was determined. These results underscore the impact that the ligand chemical properties have on the targeting capabilities of self-assembled targeted nanoparticles and provide an engineering strategy for improving their targeting specificity.

Single-step assembly of homogenous lipid-polymeric and lipid-quantum dot nanoparticles enabled by microfluidic rapid mixing.

A key challenge in the synthesis of multicomponent nanoparticles (NPs) for therapy or diagnosis is obtaining reproducible monodisperse NPs with a minimum number of preparation steps. Here we report the use of microfluidic rapid mixing using hydrodynamic flow focusing in combination with passive mixing structures to realize the self-assembly of monodisperse lipid-polymer and lipid-quantum dot (QD) NPs in a single mixing step. These NPs are composed of a polymeric core for drug encapsulation or a QD core for imaging purposes, a hydrophilic polymeric shell, and a lipid monolayer at the interface of the core and the shell. In contrast to slow mixing of lipid and polymeric solutions, rapid mixing directly results in formation of homogeneous NPs with relatively narrow size distribution that obviates the need for subsequent thermal or mechanical agitation for homogenization. We identify rapid mixing conditions that result in formation of homogeneous NPs and show that self-assembly of polymeric core occurs independent of the lipid component, which only provides stability against aggregation over time and in the presence of high salt concentrations. Physicochemical properties of the NPs including size (35-180 nm) and zeta potential (-10 to +20 mV in PBS) are controlled by simply varying the composition and concentration of precursors. This method for preparation of hybrid NPs in a single mixing step may be useful for combinatorial synthesis of NPs with different properties for imaging and drug delivery applications.

Polymeric nanoparticles for drug delivery.

The use of biodegradable polymeric nanoparticles (NPs) for controlled drug delivery has shown significant therapeutic potential. Concurrently, targeted delivery technologies are becoming increasingly important as a scientific area of investigation. In cancer, targeted polymeric NPs can be used to deliver chemotherapies to tumor cells with greater efficacy and reduced cytotoxicity on peripheral healthy tissues. In this chapter, we describe the methods of (1) preparation and characterization of drug-encapsulated polymeric NPs formulated with biocompatible and biodegradable poly(D,L-lactic-co-glycolic acid)-poly(ethylene glycol) (PLGA-b-PEG) copolymers; (2) surface functionalization of the polymeric NPs with the A10 2'-fluoropyrimidine ribonucleic acid (RNA) aptamers that recognize the prostate-specific membrane antigen (PSMA) on prostate cancer cells; and (3) evaluation of the binding properties of these targeted polymeric NPs to PSMA-expressing prostate cancer cells in vitro and in vivo. These methods may contribute to the development of other useful polymeric NPs to deliver a spectrum of chemotherapeutic, diagnostic, and imaging agents for various applications.