Differential Surface Engineering Generates Core-Shell Porous Silicon Nanoparticles for Controlled and Targeted Delivery of an Anticancer Drug

An approach to differentially modify the internal surface of porous silicon nanoparticles (pSiNPs) with hydrophobic dodecene and the external surface with antifouling poly-N-(2-hydroxypropyl) acrylamide (polyHPAm) as well as a cell-targeting peptide was developed. Specifically, to generate these core-shell pSiNPs, the interior surface of a porous silicon (pSi) film was hydrosilylated with 1-dodecene, followed by ultrasonication to create pSiNPs. The new external surfaces were modified by silanization with a polymerization initiator, and surface-initiated atom transfer radical polymerization was performed to introduce polyHPAm brushes. Afterward, a fraction of the polymer side chain hydroxyl groups was activated to conjugate cRGDfK─a peptide with a high affinity and selectivity for the α_νβ₃ integrin receptor that is overexpressed in prostate and melanoma cancers. Finally, camptothecin, a hydrophobic anti-cancer drug, was successfully loaded into the pores. This drug delivery system showed excellent colloidal stability in a cell culture medium, and the in vitro drug release kinetics could be fine-tuned by the combination of internal and external surface modifications. In vitro studies by confocal microscopy and flow cytometry revealed improved cellular association attributed to cRGDfK. Furthermore, the cell viability results showed that the drug-loaded and peptide-functionalized nanoparticles had enhanced cytotoxicity toward a C4-2B prostate carcinoma cell line in both 2D cell culture and a 3D spheroid model.

Simultaneously Defined Semiconducting Channel Layer Using Electrohydrodynamic Jet Printing of a Passivation Layer for Oxide Thin-Film Transistors

A simple fabrication method for homojunction-structured Al-doped indium-tin oxide (ITO) thin-film transistors (TFTs) using an electrohydrodynamic (EHD) jet-printed Al₂O₃ passivation layer with specific line (W_Al2O3) is proposed. After EHD jet printing, the specific region of the ITO film below the Al₂O₃ passivation layer changes from a conducting electrode to a semiconducting channel layer simultaneously upon the formation of the passivation layer during thermal annealing. The channel length of the fabricated TFTs is defined by W_Al2O3, which can be easily changed with varying EHD jet printing conditions, i.e., no need of replacing the mask for varying patterns. Accordingly, the drain current and resistance of the fabricated TFTs can be modified by varying the W_Al2O3. Using the proposed method, a transparent n-type metal-oxide-semiconductor (NMOS) inverter with an enhancement load can be fabricated; the effective resistance of load and drive TFTs is easily tuned by varying the processing conditions using this simple method. The fabricated NMOS inverter exhibits an output voltage gain of 7.13 with a supply voltage of 10 V. Thus, the proposed approach is promising as a low-cost and flexible manufacturing system for multi-item small-lot-sized production of Internet of Things devices.

Porous Si Microparticles Infiltrated with Magnetic Nanospheres

Porous silicon (pSi) microparticles obtained by porosification of crystalline silicon wafers have unique optical properties that, together with biodegradability, biocompatibility and absence of immunogenicity, are fundamental characteristics to candidate them as tracers in optical imaging techniques and as drug carriers. In this work, we focus on the possibility to track down the pSi microparticles also by MRI (magnetic resonance imaging), thus realizing a comprehensive tool for theranostic applications, i.e., the combination of therapy and diagnostics. We have developed and tested an easy, quick and low-cost protocol to infiltrate the COOH-functionalized pSi microparticles pores (tens of nanometers about) with magnetic nanospheres (SPIONs-Super Paramagnetic Iron Oxide Nanoparticles, about 5-7 nm) and allow an electrostatic interaction. The structural properties and the elemental composition were investigated by electron microscopy techniques coupled to elemental analysis to demonstrate the effective attachment of the SPIONs along the pores' surface of the pSi microparticles. The magnetic properties were investigated under an external magnetic field to determine the relaxivity properties of the material and resulting in an alteration of the relaxivity of water due to the SPIONs presence, clearly demonstrating the effectiveness of the easy functionalization protocol proposed.

TiO2-coated luminescent porous silicon micro-particles as a promising system for nanomedicine

Porous silicon (pSi) is a sponge-like material obtained by electrochemical etching of a crystalline silicon wafer. Due to quantum confinement effects, this material is photoluminescent and this is a fundamental property from the perspective of bioimaging applications. Limitations in nanomedicine to the use of photoluminescent pSi structures are mainly due to optical quenching in an aqueous environment and to the adverse effects of reactive groups introduced by etching procedures. In this work, we exploited an inorganic TiO₂ coating of pSi microparticles by Atomic Layer Deposition (ALD) that resulted in optical stability of pSi particles in a biological buffer (e.g. PBS). The use of a rotary reactor allows deposition of a uniform coating on the particles and enables a fine tuning of its thickness. The ALD parameters were optimized and the photoluminescence (PL) of pSi-TiO₂ microparticles was stabilized for more than three months without any significant effect on their morphology. The biocompatibility of the coated microparticles was evaluated by analyzing the release of cytokines and superoxide anion (O₂ ^-) by human dendritic cells, which play an essential role in the regulation of inflammatory and immune responses. We demonstrated that the microparticles per se are unable to significantly damage or stimulate human dendritic cells and therefore are suitable candidates for nanomedicine applications. However, a synergistic effect of the microparticles with bacterial products, which are known to stimulate immune-response, was observed, indicating that a condition unfavorable to the use of inorganic nanomaterials in biological systems is the presence of infection diseases. These results, combined with the proved PL stability in biological buffers, open the way for the use of pSi-TiO₂ microparticles as promising materials in nanomedicine, but their ability to increase immune cell activation by other agonists should be considered and even exploited.