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Rational design for the controlled aggregation of gold nanorods via phospholipid encapsulation for enhanced Raman scattering.

This study describes a procedure that found a balance between the ability of polymer-stabilized nanorods (NRs) to self-assemble and the creation of narrow gaps to make reproducibly bright surface-enhanced Raman scattering (SERS) nanorod dimers. NRs were end-functionalized with polymers, which enabled end-to-end self-assembly of NR chains and control over inter-rod separation through polymer molecular weight (MW). We found a way to quench the self-assembly, by phospholipid encapsulation, reducing the polydispersity of the aggregates while rendering them water-soluble. This reduction in polydispersity and preferential isolation of short-chain nanorod species is important for maximizing SERS enhancement from nanorod chains. We prepared NR aggregates that exhibit ∼5-50 times greater SERS intensity than isolated rods (and ∼750× greater than bare dye) depending on inter-rod separation, when using Oxazine 725 reporter molecules. Colloidal stability of NR aggregates and temporal stability of the SERS signal in water were observed for 110 days. With enhanced SERS intensity, water solubility, and stability, these NR aggregates are promising optical probes for future biological applications.

The effect of periodicity on the extraordinary optical transmission of annular aperture arrays

This work systematically evaluates the effect of array periodicity on the near infrared transmission characteristics of annular aperture arrays (AAAs) in gold films. Both the experimental and theoretical transmission spectra of AAAs are shown to be sensitive to the period and the arrangement of the apertures within the array. The spectra of square arrays with periods ranging from 1400 to 600 nm show a strong correlation with surface plasmon polariton (SPP)-Bloch modes of the metal/dielectric interfaces. For rectangular AAAs the transmission spectra are significantly attenuated and reveal a polarization sensitivity that arises from the breaking of the symmetry and degeneracy of the SPP-Bloch modes.

Phospholipid Membrane Encapsulation of Nanoparticles for Surface-Enhanced Raman Scattering

Lipid-encapsulated surface-enhanced Raman scattering (SERS) nanoparticles, with promising applications in biomedical diagnostics, were produced. Gold nanoparticles, 60 nm in diameter, were coated with a ternary mixture of DOPC, sphingomyelin, and cholesterol. The lipid layer is versatile for engineering the chemical and optical properties of the particles. The stability of the lipid-encapsulated particles is demonstrated over a period of weeks. The versatility of the layer is demonstrated by the incorporation of three different Raman-active species using three different strategies. The lipid layer was directly observed by TEM, and the SERS spectrum of the three dye species was confirmed by Raman spectroscopy. UV-vis absorption and dynamic light scattering provide additional evidence of lipid encapsulation. The encapsulation is achieved in aqueous solution, avoiding phase transfer and possible contamination from organic solvents. Furthermore, when fluorescent dye-labeled lipids were employed in the encapsulant, the fluorescence and SERS activity of the particles were controlled by the use of dissolved ions in the preparation solution.

Phase segregation of untethered zwitterionic model lipid bilayers observed on mercaptoundecanoic-acid-modified gold by AFM imaging and force mapping.

Planar supported lipid bilayers (SLBs) are often studied as model cell membranes because they are accessible to a variety of surface-analytic techniques. Specifically, recent studies of lipid phase coexistence in model systems suggest that membrane lateral organization is important to a range of cellular functions and diseases. We report the formation of phase-segregated dioleoylphosphatidylcholine (DOPC)/sphingomyelin/cholesterol bilayers on mercaptoundecanoic-acid-modified (111) gold by spontaneous fusion of unilamellar vesicles, without the use of charged or chemically modified headgroups. The liquid-ordered (l(o)) and liquid-disordered (l(d)) domains are observed by atomic force microscopy (AFM) height and phase imaging. Furthermore, the mechanical properties of the bilayer were characterized by force-indentation maps. Fits of force indentation to Sneddon mechanics yields average apparent Youngs moduli of the l(o) and l(d) phases of 100 +/- 2 and 59.8 +/- 0.9 MPa, respectively. The results were compared to the same lipid membrane system formed on mica with good agreement, though modulus values on mica appeared higher. Semiquantitative comparisons suggest that the mechanical properties of the l(o) phase are dominated by intermolecular van der Waals forces, while those of the fluid l(d) phase, with relatively weak van der Waals forces, are influenced appreciably by differences in surface charge density between the two substrates, which manifests as a difference in apparent Poisson ratios.

Microfluidics: a transformational tool for nanomedicine development and production

Abstract Microfluidic devices are mircoscale fluidic circuits used to manipulate liquids at the nanoliter scale. The ability to control the mixing of fluids and the continuous nature of the process make it apt for solvent/antisolvent precipitation of drug-delivery nanoparticles. This review describes the use of numerous microfluidic designs for the formulation and production of lipid nanoparticles, liposomes and polymer nanoparticles to encapsulate and deliver small molecule or genetic payloads. The advantages of microfluidics are illustrated through examples from literature comparing conventional processes such as beaker and T-tube mixing to microfluidic approaches. Particular emphasis is placed on examples of microfluidic nanoparticle formulations that have been tested in vitro and in vivo. Fine control of process parameters afforded by microfluidics, allows unprecedented optimization of nanoparticle quality and encapsulation efficiency. Automation improves the reproducibility and optimization of formulations. Furthermore, the continuous nature of the microfluidic process is inherently scalable, allowing optimization at low volumes, which is advantageous with scarce or costly materials, as well as scale-up through process parallelization. Given these advantages, microfluidics is poised to become the new paradigm for nanomedicine formulation and production.

Field localization in very small aperture lasers studied by apertureless near-field microscopy.

Localized surface plasmon polaritons (SSPs) have been observed on very small aperture lasers using apertureless near-field microscopy. Fields around multiple apertures are shown to result from interferences of SPP point sources at each aperture and optical fields. The near-field optical pattern around a single aperture indicates the interference of SPPs with their scattered counterparts. Near-field measurements also confirmed a preferred orientation of the rectangular aperture waveguide for the signal localization in very small aperture lasers.

Lipid-encapsulation of surface enhanced Raman scattering (SERS) nanoparticles and targeting to chronic lymphocytic leukemia (CLL) cells

60 nm diameter gold nanoparticles (AuNP) were coated with a ternary mixture of lipids and targeted to human lymphocytes. Previously, the versatility, stability and ease of application of the lipid coating was demonstrated by the incorporation of three classes of Raman-active species. In the present study, lipid encapsulated AuNPs were conjugated to two targeting species, namely whole antibodies and antibody fragments (Fab), by two methods. Furthermore, in vitro targeting of lipid-encapsulated Au nanoparticles to patient-derived chronic lymphocytic leukemia (CLL) cells was demonstrated by Raman spectroscopy, Raman mapping, and darkfield microscopy. These results further demonstrate the versatility of the lipid layer for imparting stability, SERS activity, and targeting capability, which make these particles promising candidates for biodiagnostics.

Microfluidic Assembly To Synthesize Dual Enzyme/Oxidation-Responsive Polyester-Based Nanoparticulates with Controlled Sizes for Drug Delivery

Controlling the size and narrow size distribution of polymer-based nanocarriers for targeted drug delivery is an important parameter that significantly influences their colloidal stability, biodistribution, and targeting ability. Herein, we report a high-throughput microfluidic process to fabricate colloidally stable aqueous nanoparticulate colloids with tunable sizes at 50-150 nm and narrow size distribution. The nanoparticulates are designed with different molecular weight polyesters having both ester bonds (responsive to esterase) and sulfide linkages (to oxidative reaction) on the backbones, thus exhibiting dual esterase/oxidation responses, causing the destabilization of the nanoparticulates to lead to the controlled release of encapsulated therapeutics. The systematic investigation on both microfluidic and formulation parameters enables to control their properties as allowing for decreasing nanoparticulate sizes as well as improving colloidal stability and cytotoxicity. Further to such control over smaller size and narrow size distribution, dual stimuli-responsive degradation and excellent cellular uptake could suggest that the microfluidic nanoparticulates stabilized with polymeric stabilizers could offer the versatility toward dual smart drug delivery exhibiting enhanced release kinetics.

Photonic Nanoparticles for Cellular and Tissular Labeling

Nanotechnology has made significant contributions to biomedical sciences, and an important example is the pervasive use of colloidal nanoparticles, whose tunable optical properties and surface chemistries have contributed largely to their versatility. Prominent among these applications is their use as targeted optical probes in cellular and tissular investigations both in vivo and in vitro. This chapter focuses on metallic and semiconductor nanoparticles, summarizing their physical and optical properties, highlighting their advantage as fluorescence, colorimetric, Raman, and optoacoustic probes, and reviewing surface chemical modifications and particle targeting strategies. Current trends in research are illustrated through numerous examples from primary literature. The growing interest in pursuing medical applications has raised questions about their toxicity, biocompatibility, and long-term accumulation, and hence this chapter also examines current studies of cellular and animal toxicity and biodistribution of metallic and semiconductor nanoparticles. Growing trends and future perspectives in the field are highlighted.

A Scalable Microfluidic Platform for the Development of LipidNanoparticles for Gene Delivery

Extended Abstract Microfluidic devices have been broadly used to produce nucleic acid-delivery nanoparticles for genetic medicine because they offer control, reproducibility and scalability of the nanoparticle precipitation process to overcome a significant challenge in the translation of these therapeutics [1-5]. Control over process parameters afforded by microfluidics, allows optimization of nanoparticle quality and encapsulation efficiency [2]. Automation improves the reproducibility and optimization of formulations. The continuous nature of the microfluidic process is inherently scalable, allowing optimization at low volumes to conserve scarce or costly materials, and seamless scale-up of optimized formulations by employing multiple microfluidic mixers performing identical unit operations in parallel. In this study, we present a scalable microfluidic platform for producing nanomedicines. The platform includes a system designed for production under cGMP conditions employing 8 parallel microfluidic mixers capable of producing a 25 L formulation of RNA lipid nanoparticles (LNP) in ~4 h. Seamless scale up of production was demonstrated by producing test batches of siRNA-LNPs against the blood clotting protein Factor VII (FVII) on each of 3 systems designed for different stages of nanomedicine development. The physico-chemical characteristics were determined by DLS, and HPLC, and in vivo efficacy was measured by assaying serum FVII levels in murine models. With a system designed for bench-scale formulation development we produced 10 mL batches of siRNA LNPs of avg. diameter ~60 nm (PDI <0.1) with encapsulation efficiency >95 %. No differences were observed in physicochemical properties of these particles when batch sizes were scaled-up by 10x on a pre-clinical scale-up system or by 100x with a system employing 8 microfluidic chips arrayed in parallel. The particles exhibited consistent lipid composition and N/P ratio within the target specifications. In addition, nanoparticles manufactured across the microfluidic platform showed a similar dose-dependent gene knockdown achieving >90 % reduction in protein levels at a dose of 1 mg/kg. These studies demonstrated the seamless scale-up of nanoparticle formulations across the platform with the potential for producing large scale, clinically relevant volumes, of lipid nanoparticles. The system employing 8 parallel mixers can prepare up to 25 L of product under 4.5 hours at 12 mL/min per mixer and incorporates a disposable fluid path that eliminates the need for costly and time consuming cleaning validation.