High‐Resolution Label‐Free Detection of Biocompatible Polymeric Nanoparticles in Cells

The design of efficient drug nanocarriers necessitates a deep understanding of their interaction with targeted cells. Polymeric poly(lactic acid) (PLA) or poly(d ,l ‐lactic‐co‐glycolic acid) nanoparticles (NPs) with sizes lower than 200 nm are among the most employed nanocarriers in drug delivery. Their detection inside cells requires appropriate labeling for high‐resolution imaging techniques, which unfortunately often alter their physicochemical properties and biological fate. Moreover, nowadays no high‐resolution method allows precise detection simultaneously to the identification of NPs chemical composition in cells, which is of outmost interest to gain insights on their fate. Here, this challenge is addressed by using an innovative atomic force microscope coupled with a tunable infrared laser source (nanoIR). NanoIR is used to unambiguously identify PLA NPs of around 170 nm with high resolution. A reliable, nondestructive, and direct method able to precisely locate and chemically characterize PLA NPs within a cell without the need of labeling is presented.     

Biocompatible Lipid‐Coated Persistent Luminescent Nanoparticles for In Vivo Imaging of Dendritic Cell Migration

Dendritic cell (DC)‐based vaccines for immunotherapy have already achieved promising results in the last decade. To further improve current treatment protocols and enhance the therapeutic outcome, noninvasive in vivo tracking of DCs remains of crucial importance. Persistent luminescent nanoparticles (PLNPs) are inorganic materials which show an afterglow for hours after the optical excitation has ceased. If the afterglow is in the near‐infrared, the emission of injected particles can be tracked in vivo. However, stability and toxicity issues limit the use of bare PLNPs for biological applications. Therefore, appropriate surface functionalization is needed to improve their biocompatibility. In this study, it is demonstrated that near‐infrared light emitting LiGa₅O₈:Cr³⁺ nanoparticles can be functionalized with a biocompatible lipid coating which provides them with outstanding stability in biological media. In vitro experiments show efficient uptake, absence of cytotoxicity even at very high particle concentrations, and no adverse effects on the maturation potential of DCs. DCs labeled with lipid‐coated LiGa₅O₈:Cr³⁺ nanoparticles injected in mice can be imaged over days, confirming efficient in vivo migration to the popliteal lymph node. Together the results show that lipid coated LiGa₅O₈:Cr³⁺ nanoparticles possess excellent possibilities for further use in research and development of DC based vaccines.     

Colloidal Nanoparticles: Formation of Large 2D Arrays of Shape‐Controlled Colloidal Nanoparticles at Variable Interparticle Distances (Part. Part. Syst. Charact. 1/2013)

A method for the production of homogeneous layers of nanoparticles of arbitrary shape is presented. The method relies on a ligand exchange with a functionalized polymer and a subsequent self‐assembly of a thin film on the substrates. The interparticle distances in the layer can be adjusted by the length of the polymer. In the case of spherical particles, the approach yields quasi‐hexagonal structures; in the case of anisotropic particles, the minimum distance between adjacent particles is controlled. Regular arrangements of the nanoparticles covering areas of several square centimeters are achieved.     

Red Emissive Biocompatible Nanoparticles from Tetraphenylethene‐Decorated BODIPY Luminogens for Two‐Photon Excited Fluorescence Cellular Imaging and Mouse Brain Blood Vascular Visualization

BODIPY (4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene) is an emissive chromophore in solutions but suffers from fluorescence quenching when aggregated due to its flat molecular conformation and small Stokes shift. To create aggregate‐state emissive BODIPY luminogens, tetraphenylethene (TPE), which is a popular luminogen with intriguing aggregation‐induced emission (AIE) characteristic, is introduced as periphery to a methylated BODIPY core. Three TPE‐BODIPY adducts are synthesized and characterized, and their photophysical properties and electronic structures are investigated. The incorporation of AIE‐active TPE units alleviates aggregation‐caused quenching of BODIPY core, furnishing emissive nanoparticles based on TPE‐BODIPY adducts. Significantly, the two‐photon absorption (TPA) and two‐photon excited fluorescence (TPEF) properties are improved as more TPE units are attached. The luminogens with 3TPE units (3TPE‐BODIPY) shows the strongest TPA and TPEF in the wavelength range of 750–830 nm, with cross‐section values of 264 and 116 GM at 810 nm, respectively. Red emissive nanoparticles with a Stokes shift of 60 nm and a fluorescence quantum yield of 16% are attained by encapsulating 3TPE‐BODIPY with 1,2‐sistearoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐[methoxy(polyethylene glycol)‐2000]. The nanoparticles are biocompatible and function well in TPEF cellular imaging and mouse brain blood vascular visualization.     

Inkjet-Based Technology for Microencapsulation of Gold Nanoparticles within Biocompatible Hydrogels

Herein, an inkjet-based technology as a versatile high throughput methodology for the microencapsulation of gold nanoparticles (AuNPs) inside a biocompatible chitosan hydrogel is described. This continuous automated inkjet production approach generates 30 µm diameter polymeric microcapsules and offers a high rate of production and nanoparticle encapsulation efficiency of 14 nm diameter AuNPs, precise control of the microcapsule size, and ease of scale-up. The hybrid microcapsules demonstrate biocompatible cell-adhesion properties and resist degradation over a large range of pH, making them particularly relevant for a variety of potential health applications.     

Microwave‐Assisted Synthesis of Biocompatible Silk Fibroin‐Based Carbon Quantum Dots

A biocompatible silk fibroin‐based carbon quantum dot (SF‐CQD) is first synthesized under microwave irradiation for a short time. This fast and environmentally safe technique produce well‐defined nanosized SF‐CQDs. The SF‐CQDs have good crystallinity, a strong emission peak in the blue‐color region, high quantum yield, and the potential for modification with various functional groups on the surface. These SF‐CQDs demonstrate stable emission, good water dispersity, low toxicity, and good biocompatibility. These properties show the great potential of these SF‐CQDs for use in biomedical applications including bioimaging, biosensing, and drug delivery systems.