In this account, we varied PEGylation density on the surface of hydrogel PRINT nanoparticles and systematically observed the effects on protein adsorption, macrophage uptake, and circulation time. Interestingly, the density of PEGylation necessary to promote a long-circulating particle was dramatically less than what has been previously reported. Overall, our methodology provides a rapid screening technique to predict particle behavior in vivo and our results deliver further insight to what PEG density is necessary to facilitate long-circulation.

It has long been hypothesized that elastic modulus governs the biodistribution and circulation times of particles and cells in blood; however, this notion has never been rigorously tested. We synthesized hydrogel microparticles with tunable elasticity in the physiological range, which resemble red blood cells in size and shape, and tested their behavior in vivo. Decreasing the modulus of these particles altered their biodistribution properties, allowing them to bypass several organs, such as the lung, that entrapped their more rigid counterparts, resulting in increasingly longer circulation times well past those of conventional microparticles. An 8-fold decrease in hydrogel modulus correlated to a greater than 30-fold increase in the elimination phase half-life for these particles. These results demonstrate a critical design parameter for hydrogel microparticles.biomimetic | deformability | drug carriers | long circulating | red blood cell mimic

CONSPECTUS Nanotheranostics represents the next generation of medicine, fusing nanotechnology, therapeutics, and diagnostics. By integrating therapeutic and imaging agents into one nanoparticle, this new treatment strategy has the potential not only to detect and diagnose disease but also to treat and monitor the therapeutic response. This capability could have a profound impact in both the research setting as well as in a clinical setting. In the research setting, such a capability will allow research scientists to rapidly assess the performance of new therapeutics in an effort to iterate their designs for increased therapeutic index and efficacy. In the clinical setting, theranostics offers the ability to determine whether patients enrolling in clinical trials are responding, or are expected to respond, to a given therapy based on the hypothesis associated with the biological mechanisms being tested. If not, patients can be more quickly removed from the clinical trial and shifted to other therapeutic options. To be effective, these theranostic agents must be highly site specific. Optimally, they will carry relevant cargo, demonstrate controlled release of that cargo, and include imaging probes with a high signal-to-noise ratio. There are many biological barriers in the human body that challenge the efficacy of nanoparticle delivery vehicles. These barriers include, but are not limited to, the walls of blood vessels, the physical entrapment of particles in organs, and the removal of particles by phagocytic cells. The rapid clearance of circulating particles during systemic delivery is a major challenge; current research seeks to define key design parameters that govern the performance of nanocarriers, such as size, surface chemistry, elasticity, and shape. The effect of particle size and surface chemistry on in vivo biodistribution of nanocarriers has been extensively studied, and general guidelines have been established. Recently it has been documented that shape and elasticity can have a profound effect on the behavior of delivery vehicles. Thus, having the ability to independently control shape, size, matrix, surface chemistry, and modulus is crucial for designing successful delivery agents. In this Account, we describe the use of particle replication in nonwetting templates (PRINT) to fabricate shape- and size-specific microparticles and nanoparticles. A particular strength of the PRINT method is that it affords precise control over shape, size, surface chemistry, and modulus. We have demonstrated the loading of PRINT particles with chemotherapeutics, magnetic resonance contrast agents, and fluorophores. The surface properties of the PRINT particles can be easily modified with “stealth” poly(ethylene glycol) chains to increase blood circulation time, with targeting moieties for targeted delivery or with radiolabels for nuclear imaging. These particles have tremendous potential for applications in nanomedicine and diagnostics.

The search for a method to fabricate non-spherical colloidal particles from a variety of materials is of growing interest. As the commercialization of nanotechnology continues to expand, the ability to translate particle fabrication methods from a laboratory to an industrial scale is of increasing significance. In this article, we examine several of the most readily scalable top-down methods for the fabrication of such shape specific particles and compare their capabilities with respect to particle composition, size, shape and complexity as well as the scalability of the method. We offer an extensive examination of Particle Replication In Non-wetting Templates (PRINT®) with regards to the versatility and scalability of this technique. We also detail the specific methods used in PRINT particle fabrication, including harvesting, purification and surface modification techniques, with examination of both past and current methods.

This review discusses rational design of particles for use as therapeutic vectors and diagnostic imaging agent carriers. The emerging importance of both particle size and shape is considered, and the adaptation and modification of soft lithography methods to produce nanoparticles is highlighted. To this end, studies utilizing particles made via a process called Particle Replication In Non-wetting Templates (PRINT ™ ) are discussed. In addition, insights gained into therapeutic cargo and imaging agent delivery from related types of polymer-based carriers are considered. KeywordsPRINT; nanoparticles; diagnostic imaging; therapeutic drug delivery; shape With rapid development of new pharmaceuticals and contrast agents, the need for the minimization of side effects in concert with simultaneous targeted delivery to specific tissues of interest continues to expand. Overcoming barriers for effective bioavailability of therapeutic agents has been especially challenging in the fields of gene therapy[1] and oncology. [2] As an illustration, despite their potential for wide application, only a few antisense oligonucleotides or small interfering RNA's (siRNA) have entered clinical trials. The prevalence of hydrophobic drugs also necessitates the use of nanocarriers; for these systems, direct dissolution in the bloodstream is limited without the formation of a salt or use of a delivery vector. [3] One solution to this problem is the delivery of drugs, gene therapy agents, and imaging contrast agents via nano-scale vectors, and this has been an area of intense study for decades. Although multiple approaches have been explored and strides have been made in therapeutic drug delivery and diagnostic imaging agent carriers, a set of rules for the rational design of nanocarriers has not yet been fully established due to limited understanding of how all of the carrier properties (including size and shape as well as matrix Cross-References MR relaxation properties of superparamagnetic iron oxide particles Microlithographic delivery devices Nano-encapsulation technology to deliver native protein drugs NIH Public Access Author ManuscriptWiley Interdiscip Rev Nanomed Nanobiotechnol. Author manuscript; available in PMC 2010 July 1. Published in final edited form as:Wiley Interdiscip Rev Nanomed Nanobiotechnol. Rational Design of Drug and Contrast Agent CarriersSeveral critical factors that must be considered in the design of contrast agent and/or polymeric drug carriers include the chemical functionality and mechanical flexibility of the matrix, the degree of cross-linking, if any, the dispersion or encapsulation of the drug within the matrix, the permeability of the cargo through the matrix of the particle, the number and the nature of phases that comprise the particle (one phase versus two or more phases e. g. drug rich phase and matrix rich phase,) the size and shape of the particle, and the surface chemistry. Many of these factors need to be studied and controlled in particle design for the delivery of imaging contrast agent...

Scalable methods, PRINT® particle fabrication and spray-assisted Layer-by-Layer deposition, are combined to generate uniform and functional nanotechnologies with precise control over composition, size, shape, and surface functionality. A modular and tunable approach towards design of built-to-order nanoparticle systems, spray coating on PRINT® particles is demonstrated to achieve technologies capable of targeted interactions with cancer cells for applications in drug delivery.

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Micrometer-sized monodisperse anisotropic polymer particles, with disk, rod, fenestrated hexagon (hexnut), and boomerang shapes, were synthesized using the particle replication in nonwetting templates (PRINT) process, and investigations were conducted on aqueous suspensions of these particles when subjected to alternating electric fields. A coplanar electrode configuration, with 1 to 2 mm electrode gaps (20-50 V ac, 0.5-5.0 kHz) was used, and the experiments were monitored with fluorescence microscopy. For all particle suspensions, the field brought about significant changes in the packing and orientation. Extensive particle chaining and packing were observed for the disk, rod, and hexnut suspensions. Because of the size and geometry of the boomerang particles, limited chaining was observed; however, the field triggered a change from random to a more ordered packing arrangement.