Erik Pierstorff

Nanodiamond-mediated delivery of water-insoluble therapeutics.

A broad array of water-insoluble compounds has displayed therapeutically relevant properties toward a spectrum of medical and physiological disorders, including cancer and inflammation. However, the continued search for scalable, facile, and biocompatible routes toward mediating the dispersal of these compounds in water has limited their widespread application in medicine. Here we demonstrate a platform approach of water-dispersible, nanodiamond cluster-mediated interactions with several therapeutics to enhance their suspension in water with preserved functionality, thereby enabling novel treatment paradigms that were previously unrealized. These therapeutics include Purvalanol A, a highly promising compound for hepatocarcinoma (liver cancer) treatment, 4-hydroxytamoxifen (4-OHT), an emerging drug for the treatment of breast cancer, as well as dexamethasone, a clinically relevant anti-inflammatory that has addressed an entire spectrum of diseases that span complications from blood and brain cancers to rheumatic and renal disorders. Given the scalability of nanodiamond processing and functionalization, this novel approach serves as a facile, broadly impacting and significant route to translate water-insoluble compounds toward treatment-relevant scenarios.

Protein-Mediated Assembly of Nanodiamond Hydrogels into a Biocompatible and Biofunctional Multilayer Nanofilm

Aqueous dispersible detonation nanodiamonds (NDs) with a diameter of 2-8 nm were assembled into a closely packed ND multilayer nanofilm with positively charged poly-L-lysine via the layer-by-layer deposition technique. The innate biocompatibility of the NDs in both free-floating and thin-film forms was confirmed via cellular gene expression examination by real-time polymerase chain reaction as well as MTT and DNA fragmentation assays. The highly biologically amenable ND nanofilm was successfully integrated with therapeutic molecules, and the functionality of the composite drug-ND material was assessed via interrogation of the suppression of inflammatory cytokine release. Knockdown of lipopolysaccharide-mediated inflammation was observed through the potent attenuation of tumor necrosis factor-alpha, interleukin-6, and inducible nitric oxide synthase levels following ND nanofilm interfacing with RAW 264.7 murine macrophages. Furthermore, basal cytokine secretion levels were assessed to examine innate material biocompability, revealing unchanged cellular inflammatory responses which strongly supported the relevance of the NDs as effective treatment platforms for nanoscale medicine. In addition to the easy preparation, robustness, and fine controllability of the film structures, these hybrid materials possess enormous potential for biomedical applications such as localized drug delivery and anti-inflammatory implant coatings and devices, as demonstrated in vitro in this work.

Nanodiamond-Embedded Microfilm Devices for Localized Chemotherapeutic Elution

Nanodiamonds (NDs) of 2-8 nm diameters physically bound with the chemotherapeutic agent doxorubicin hydrochloride (DOX) were embedded within a parylene C polymer microfilm through a facile and scalable process. The microfilm architecture consists of DOX-ND conjugates sandwiched between a base and thin variable layer of parylene C which allows for modulation of release. Successive layers of parylene and the DOX-ND conjugates were characterized through atomic force microscopy (AFM) images and drug release assays. Elution rates were tested separately over a period of 8 days and up to one month in order to illustrate the release characteristics of the microfilms. The microfilms displayed the stable and continuous slow-release of drug for at least one month due to the powerful sequestration abilities of the DOX-ND complex and the release-modulating nature of the thin parylene layer. Since the fabrication process is devoid of any destructive steps, the DOX-ND conjugates are unaffected and unaltered. A DNA fragmentation assay was performed to illustrate this retained activity of DOX under biological conditions. Specifically, in this work we have conferred the ability to tangibly manipulate the NDs in a polymer-packaged microfilm format for directed placement over diseased areas. By harnessing the innate ND benefits in a biostable patch platform, extended targeted and controlled release, possibly relevant toward conditions such as cancer, viral infection, and inflammation, where complementary alternatives to systemic drug release enabled by the microfilm devices, can allow for enhanced treatment efficacy.

Reservoir-Based Polymer Drug Delivery Systems

The importance of drug delivery has increased over the past decades, and significant advances have been made in the development of novel technologies. This review focuses on the use of different polymer drug delivery systems and their advancement toward clinical applications.

Copolymeric nanofilm platform for controlled and localized therapeutic delivery.

Nanomaterials such as block copolymeric membranes provide a platform for both cellular interrogation and biological mimicry. Their biomimetic properties are based upon the innate possession of hydrophilic and hydrophobic units that enable their integration with a broad range of therapeutic materials. As such, they can be engineered for specific applications in nanomedicine, including controlled/localized drug delivery. Here we describe a method for the functionalization of the polymethyloxazoline-polydimethylsiloxane-polymethyloxazoline (PMOXA-PDMS-PMOXA) block copolymer with anti-inflammatory molecules to develop copolymer-therapeutic hybrids, effectively conferring biological functionality to a versatile synthetic nanomembrane matrix and creating a platform for an anti-inflammatory drug delivery system. Utilizing self-assembly and Langmuir-Blodgett deposition methods, we mixed copolymers with dexamethasone (Dex), an anti-inflammatory glucocorticoid receptor agonist. The successful mixing of the copolymer with the drug was confirmed by surface pressure isotherms and fluorescence microscopy. Furthermore, at 4 nm thick per layer, orders of magnitude thinner than conventional drug delivery coatings, these dexamethasone-copolymer mixtures (PolyDex) suppressed in vitro expression of the inflammatory cytokines/signaling elements interleukin 6 (IL-6), interleukin 12 (IL-12), tumor necrosis factor alpha (TNFalpha), inducible nitric oxide synthase (iNOS), and interferon gamma inducible protein (IP-10). Finally, PolyDex maintained its anti-inflammatory properties in vivo confirmed through punch biopsies with tissue imagery via hematoxylin/eosin and macrophage specific staining using CD11b. Thus, we demonstrated that PolyDex may be utilized as a localized, highly efficient drug-copolymer composite for active therapeutic delivery to confer anti-inflammatory protection or as a platform material for broad drug elution capabilities.

Localized therapeutic release via an amine-functionalized poly-p-xylene microfilm device.

Developing biocompatible polymeric platforms for drug delivery with enhanced localized activity represents a key facet of advanced interventional therapy. In this work, the drug-eluting potential of an amine-functionalized poly- p-xylene commonly known as Parylene A (4-amino(2,2)paracyclophane) was conducted with the microfilm device consisting of a primary base layer, drug film, and a secondary eluting layer presenting exposed amine groups which enhance the range of modifications that can be incorporated into the film. The murine macrophage cell line RAW 264.7 served as a cellular response to dexamethasone, a synthetic anti-inflammatory glucocorticoid and doxorubicin, an anticancer therapeutic. Decreased expression of NFkappa-B-mediated cytokines Interleukin-6 (IL-6) and Tumor Necrosis Factor-alpha (TNFalpha), resultant DNA fragmentation, and spectroscopic analysis revealed the efficient and localized drug-eluting properties of the Parylene A polymeric bilayer.

Nanomembrane-driven co-elution and integration of active chemotherapeutic and anti-inflammatory agents

The release of therapeutic drugs from the surface of implantable devices is instrumental for the reduction of medical costs and toxicity associated with systemic administration. In this study we demonstrate the triblock copolymer-mediated deposition and release of multiple therapeutics from a single thin film at the air-water interface via Langmuir–Blodgett deposition. The dual drug elution of dexamethasone (Dex) and doxorubicin hydrochloride (Dox) from the thin film is measured by response in the RAW 264.7 murine macrophage cell line. The integrated hydrophilic and hydrophobic components of the polymer structure allows for the creation of hybrids of the copolymer and the hydrophobic Dex and the hydrophilic Dox. Confirmation of drug release and functionality was demonstrated via suppression of the interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF α) inflammatory cytokines (Dex), as well as TUNEL staining and DNA fragmentation analysis (Dox). The inherent biocompatibility of the copolymeric material is further demonstrated by the lack of inflammation and apoptosis induction in cells grown on the copolymer films. Thus a layer-by-layer anchored deposition of an anti-inflammatory and chemotherapeutic functionalized copolymer film is able to localize drug dosage to the surface of a medical device, all with an innate material thickness of 4 nm per layer.

Attenuation of Cellular Inflammation Using Glucocorticoid-Functionalized Copolymers

This work has demonstrated the functionalization of an amphiphilic diblock copolymer, comprised of polyethylene oxide-polymethyl methacrylate (PEO-PMMA), as well as a triblock copolymer comprised of polymethyloxazoline-polydimethylsiloxane-polymethyloxazoline(PMOXA-PDMS-PM OXA) with the dexamethasone (Dex) glucocorticoid anti-inflammatory. Interfacial deposition of the copolymer and the Dex molecules and subsequent transfer of the hybrid materials to solid substrates were characterized to evaluate the potential of utilizing this composite material as a suppressor of cyto-inflammation to enhance implant biocompatibility. Given the extremely thin dimensions of the film (~4nm), this material would have negligible impact upon the size of the coated device to preclude biological stress. The composite films were interfaced with the RAW264.7 murine macrophages which served as a model cell line for the evaluation of nuclear factor-kappaB (NF-KB)-induced production of a host of inflammatory cytokines including interleukin-6, interleukin-12, tumor necrosis factor-alpha (TNFalpha), as well as the inducible nitric oxide synthase signaling factor which is known to be involved with stress-related processes such as neuronal damage. Lipopolysaccharide or LPS is a component of bacterial membranes that elicits cellular stress following application to RAW cell cultures. Following the induced stress response, significant reductions in the expression of genes associated with the aforementioned cytokines and signaling molecules indicated that macrophages in direct contact with the functionalized copolymer were able to collect Dex that was released from within the polymer network to attenuate cyto-inflammation mechanisms. This composite membrane represents a medically-relevant technology to promote chronic implant functionality and preclusion of bio-fouling.

Engineering Multifunctional Biologically-Amenable Nanomaterials for Interfacial Therapeutic Delivery and Substrate-Based Cellular Interrogation

The advent of materials that can enhance the interfaces between biological tissue and engineered devices will enable unprecedented medical capabilities in the context of prolonged implantation, and novel information gleaned from cellular interrogation, etc. This work addresses a spectrum of novel technologies that can serve a broad range of therapeutically relevant scenarios ranging from inflammation attenuation to stand-alone chemotherapeutic delivery systems. They include copolymer-based multifunctional platforms that can be applied towards dynamic cell adhesion/patterning, drug delivery, and localized manipulation of key cyto-regulatory networks for clinical applications. In addition, soluble nanodiamond platforms in free-floating or thin film platforms will be addressed as next generation therapeutic vehicles. In addition to cytokine expression knockdown studies as well as in vivo validation of their efficacy, this suite of modalities successfully addresses a key element of optimized interfacing based upon innate biocompatibility which has been verified at the genetic level, confirming their potential clinical significance.

Functionalized nanodiamonds as efficient transmembrane drug carriers

Studies of the biological relevance of nanocarbon materials have attracted much attention. While the scientific community has primarily focused on the potential biological applications of fullerenes and carbon nanotubes, another important form of nanocarbon materials, nanodiamonds (NDs), are beginning to emerge as alternative candidates for similar and other applications due to their high biocompatibility, as revealed in our recent study. In this work, we present the first utilization of nanodiamond hydrogels as efficient biocompatible drug carriers. Both anti-inflammatory and anti-cancer drugs have been successfully coated on nanodiamonds and integrated into their aggregates via electrostatic and physical interactions to form slow release and targeted drug systems. In addition, in vitro studies have indicated that the NDs can efficiently carry drugs into the cells.