String-like micellar nanoparticles formed by complexation of PEG-b-PPA and plasmid DNA and their transfection efficiency

Biomimetic Anisotropic-Functionalized Platelet-Membrane-Coated Polymeric Particles for Targeted Drug Delivery to Human Breast Cancer Cells

Biomimetic particles that can replicate aspects of natural biological cell function are useful for advanced biological engineering applications. Engineering such particles requires mimicking the chemical complexity of the surface of biological cells, and this can be achieved by coating synthetic particles with naturally derived cell membranes. Past research has demonstrated the feasibility of utilizing cell membrane coatings from a variety of cell types to achieve extended blood circulation half-life. A particle's shape can also be designed to mimic a biological cell or virus, and this physical attribute can cause particular transport and biodistribution properties. However, the potential synergy between engineering a biomimetic particle's core shape in combination with functionalizing its surface with cell membranes to achieve targeted drug delivery has not been well-investigated. Here, anisotropic poly(lactic-co-glycolic acid) (PLGA) particles are coated with platelet membranes to engineer particles with enhanced stealth properties that are biomimetic in size, shape, and surface composition to natural platelets. The natural ability of platelets to target tumor cells was harnessed to develop a particulate system for targeted dual delivery of a small molecule and protein to cancer cells. The particles had targeted binding to metastatic human breast cancer cells, leading to enhanced killing of these cells in a mouse model through codelivery of TRAIL and doxorubicin. This system can be used for cancer cell killing and could potentially be utilized in preventing breast cancer metastasis. By engineering both the physical and chemical properties of the particles, biomimicry and therapeutic promise can be best achieved.

Features of Anisotropic Drug Delivery Systems

Natural materials are anisotropic. Delivery systems occurring in nature, such as viruses, blood cells, pollen, and many others, do have anisotropy, while delivery systems made artificially are mostly isotropic. There is apparent complexity in engineering anisotropic particles or capsules with micron and submicron sizes. Nevertheless, some promising examples of how to fabricate particles with anisotropic shapes or having anisotropic chemical and/or physical properties are developed. Anisotropy of particles, once they face biological systems, influences their behavior. Internalization by the cells, flow in the bloodstream, biodistribution over organs and tissues, directed release, and toxicity of particles regardless of the same chemistry are all reported to be factors of anisotropy of delivery systems. Here, the current methods are reviewed to introduce anisotropy to particles or capsules, including loading with various therapeutic cargo, variable physical properties primarily by anisotropic magnetic properties, controlling directional motion, and making Janus particles. The advantages of combining different anisotropy in one entity for delivery and common problems and limitations for fabrication are under discussion.

Polymeric Nanoparticles in Gene Therapy: New Avenues of Design and Optimization for Delivery Applications

The field of polymeric nanoparticles is quickly expanding and playing a pivotal role in a wide spectrum of areas ranging from electronics, photonics, conducting materials, and sensors to medicine, pollution control, and environmental technology. Among the applications of polymers in medicine, gene therapy has emerged as one of the most advanced, with the capability to tackle disorders from the modern era. However, there are several barriers associated with the delivery of genes in the living system that need to be mitigated by polymer engineering. One of the most crucial challenges is the effectiveness of the delivery vehicle or vector. In last few decades, non-viral delivery systems have gained attention because of their low toxicity, potential for targeted delivery, long-term stability, lack of immunogenicity, and relatively low production cost. In 1987, Felgner et al. used the cationic lipid based non-viral gene delivery system for the very first time. This breakthrough opened the opportunity for other non-viral vectors, such as polymers. Cationic polymers have emerged as promising candidates for non-viral gene delivery systems because of their facile synthesis and flexible properties. These polymers can be conjugated with genetic material via electrostatic attraction at physiological pH, thereby facilitating gene delivery. Many factors influence the gene transfection efficiency of cationic polymers, including their structure, molecular weight, and surface charge. Outstanding representatives of polymers that have emerged over the last decade to be used in gene therapy are synthetic polymers such as poly(l-lysine), poly(l-ornithine), linear and branched polyethyleneimine, diethylaminoethyl-dextran, poly(amidoamine) dendrimers, and poly(dimethylaminoethyl methacrylate). Natural polymers, such as chitosan, dextran, gelatin, pullulan, and synthetic analogs, with sophisticated features like guanidinylated bio-reducible polymers were also explored. This review outlines the introduction of polymers in medicine, discusses the methods of polymer synthesis, addressing top down and bottom up techniques. Evaluation of functionalization strategies for therapeutic and formulation stability are also highlighted. The overview of the properties, challenges, and functionalization approaches and, finally, the applications of the polymeric delivery systems in gene therapy marks this review as a unique one-stop summary of developments in this field.

Anisotropic biodegradable lipid coated particles for spatially dynamic protein presentation

There has been growing interest in the use of particles coated with lipids for applications ranging from drug delivery, gene delivery, and diagnostic imaging to immunoengineering. To date, almost all particles with lipid coatings have been spherical despite emerging evidence that non-spherical shapes can provide important advantages including reduced non-specific elimination and increased target-specific binding. We combine control of core particle geometry with control of particle surface functionality by developing anisotropic, biodegradable ellipsoidal particles with lipid coatings. We demonstrate that these lipid coated ellipsoidal particles maintain advantageous properties of lipid polymer hybrid particles, such as the ability for modular protein conjugation to the particle surface using versatile bioorthogonal ligation reactions. In addition, they exhibit biomimetic membrane fluidity and demonstrate lateral diffusive properties characteristic of natural membrane proteins. These ellipsoidal particles simultaneously provide benefits of non-spherical particles in terms of stability and resistance to non-specific phagocytosis by macrophages as well as enhanced targeted binding. These biomaterials provide a novel and flexible platform for numerous biomedical applications.

STATEMENT OF SIGNIFICANCE

The research reported here documents the ability of non-spherical polymeric particles to be coated with lipids to form anisotropic biomimetic particles. In addition, we demonstrate that these lipid-coated biodegradable polymeric particles can be conjugated to a wide variety of biological molecules in a "click-like" fashion. This is of interest due to the multiple types of cellular mimicry enabled by this biomaterial based technology. These features include mimicry of the highly anisotropic shape exhibited by cells, surface presentation of membrane bound protein mimetics, and lateral diffusivity of membrane bound substrates comparable to that of a plasma membrane. This platform is demonstrated to facilitate targeted cell binding while being resistant to non-specific cellular uptake. Such a platform could allow for investigations into how physical parameters of a particle and its surface affect the interface between biomaterials and cells, as well as provide biomimetic technology platforms for drug delivery and cellular engineering.

Shaping the future of nanomedicine: anisotropy in polymeric nanoparticle design

Nanofabrication and biomedical applications of polymeric nanoparticles have become important areas of research. Biocompatible polymeric nanoparticles have been investigated for their use as delivery vehicles for therapeutic and diagnostic agents. Although polymeric nanoconstructs have traditionally been fabricated as isotropic spheres, anisotropic, nonspherical nanoparticles have gained interest in the biomaterials community owing to their unique interactions with biological systems. Polymeric nanoparticles with different forms of anisotropy have been manufactured using a variety of novel methods in recent years. In addition, they have enhanced physical, chemical, and biological properties compared with spherical nanoparticles, including increased targeting avidity and decreased nonspecific in vivo clearance. With these desirable properties, anisotropic nanoparticles have been successfully utilized in many biomedical settings and have performed superiorly to analogous spherical nanoparticles. We summarize the current state-of-the-art fabrication methods for anisotropic polymeric nanoparticles including top-down, bottom-up, and microfluidic design approaches. We also summarize the current and potential future applications of these nanoparticles, including drug delivery, biological targeting, immunoengineering, and tissue engineering. Ongoing research into the properties and utility of anisotropic polymeric nanoparticles will prove critical to realizing their potential in nanomedicine.

Biomimetic particles as therapeutics

In recent years, there have been major advances in the development of novel nanoparticle- and microparticle-based therapeutics. An emerging paradigm is the incorporation of biomimetic features into these synthetic therapeutic constructs to enable them to better interface with biological systems. Through the control of size, shape, and material consistency, particle cores have been generated that better mimic natural cells and viruses. In addition, there have been significant advances in biomimetic surface functionalization of particles through the integration of bio-inspired artificial cell membranes and naturally derived cell membranes. Biomimetic technologies enable therapeutic particles to have increased potency to benefit human health.

Simulation and Experimental Assembly of DNA-Graft Copolymer Micelles with Controlled Morphology

Nanoparticles formed through complexation of plasmid DNA and copolymers are promising gene-delivery vectors, offering a wide range of advantages over alternative delivery strategies. Notably, recent research has shown that the shape of these particles can be tuned, which makes it possible to gain understanding of their shape-dependent transfection properties. Whereas earlier methods achieved shape tuning through the use of block copolymers and variation of solvent polarity, here we demonstrate through a combined experimental and computational approach that the same degree of shape control can be achieved through the use of graft copolymers that are easier to synthesize and provide a wider range of parameters for shape control. Moreover, the approach presented here does not require the use of organic solvents. The simulation work provides insight into the mechanism governing the shape variation as well as an effective model to guide further design of non-viral gene-delivery vectors. Our experimental findings offer important opportunities for the facile and large-scale synthesis of biocompatible gene-delivery vectors with well-controlled shape and tunable transfection properties. The in vitro study shows that both micelle shape and transfection efficiency are strongly correlated with the key structural parameters of the graft copolymer carriers.

An automated multidimensional thin film stretching device for the generation of anisotropic polymeric micro- and nanoparticles

Anisotropic polymeric particles are of growing interest for biomaterials applications due to their unique properties. These include the ability for these particles to evade nonspecific cellular uptake and to have enhanced targeted cellular uptake and interaction. One of the most widely used methods for generating anisotropic polymeric particles is the thin film stretching procedure. Despite its theoretical simplicity, this procedure, as it has been implemented to date, can be difficult due to the inconsistent nature of the manual operation of machinery used to stretch the film. We have constructed an automated thin film stretcher for control over biomaterials via thin film stretching in 1D and 2D and as a result, have enabled precise generation of anisotropic polymeric particles. We demonstrate that this device can be utilized to produce anisotropic biodegradable particles of different size, shape, and material consistency. Furthermore, we show that this machine has enabled the scaled up and rapid production of anisotropic polymeric particles, including polymeric microparticles that mimic the shape of red blood cells. Further application of this automated thin film stretching device could allow for significant impact to diverse biomaterial and biomedical applications such as biomimetic particles for immunoengineering and long-circulating particles for controlled release of drugs.

Modified dipeptide-based nanoparticles: vehicles for targeted tumor drug delivery

Aim: Different nanoparticles have been investigated to deliver chemotherapeutic agents, but complex synthesis procedures and biocompatibility issues raise concerns in developing them for safe human usage. The aim of this work is to develop α,β-dehydrophenylalanine-containing, self-assembled, amphipathic dipeptide nanoparticles for tumor-targeted drug delivery and therapy. Material & methods: Solution-phase peptide synthesis was used to synthesize dipeptides. Nanoparticles were prepared by molecular self-assembly. A tumor distribution study was carried out using a radiolabeling method. Tumor regression studies were carried out in murine ascitic tumors in BALB/c mice and breast tumor xenografts in in nonobese diabetic/severe combined immuno¬deficiency mice. Results: Arg–α,β-dehydrophenylalanine formed self-assembled nanoparticles that could be easily derivatized with folic acid. Folic acid-derivatized nanoparticles showed enhanced cellular uptake and, when loaded with doxorubicin, showed enhanced tumor regression compared with underivatized nanoparticles or native drug, without any adverse side effects, both in vitro and in vivo.

Original submitted 20 April 2012; Revised submitted 9 November 2012

Probing in vivo trafficking of polymer/DNA micellar nanoparticles using SPECT/CT imaging

Successful translation of nonviral gene delivery to therapeutic applications requires detailed understanding of in vivo trafficking of the vehicles. This report compares the pharmacokinetic and biodistribution profiles of polyethylene glycol-b-polyphosphoramidate (PEG-b-PPA)/DNA micellar nanoparticles after administration through intravenous infusion, intrabiliary infusion, and hydrodynamic injection using single photon emission computed tomography/computed tomography (SPECT/CT) imaging. Nanoparticles were labeled with (111)In using an optimized protocol to retain their favorable physicochemical properties. Quantitative imaging analysis revealed different in vivo trafficking kinetics for PEG-b-PPA/DNA nanoparticles after different routes of administration. The intrabiliary infusion resulted in the highest liver uptake of micelles compared with the other two routes. Analysis of intrabiliary infusion by the two-compartment pharmacokinetic modeling revealed efficient retention of micelles in the liver and minimal micelle leakage from the liver to the blood stream. This study demonstrates the utility of SPECT/CT as an effective noninvasive imaging modality for the characterization of nanoparticle trafficking in vivo and confirms that intrabiliary infusion is an effective route for liver-targeted delivery of DNA-containing nanoparticles.