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.

Advances in Laser Ablation Synthesized Silicon-Based Nanomaterials for the Prevention of Bacterial Infection

Nanomaterials have unique properties and characteristics derived from their shape and small size that are not present in bulk materials. If size and shape are decisive, the synthesis method used, which determines the above parameters, is equally important. Among the different nanomaterial’s synthesis methods, we can find chemical methods (microemulsion, sol-gel, hydrothermal treatments, etc.), physical methods (evaporation-condensation, laser treatment, etc.) and biosynthesis. Among all of them, the use of laser ablation that allows obtaining non-toxic nanomaterials (absence of foreign compounds) with a controlled 3D size, has emerged in recent years as a simple and versatile alternative for the synthesis of a wide variety of nanomaterials with numerous applications. This manuscript reviews the latest advances in the use of laser ablation for the synthesis of silicon-based nanomaterials, highlighting its usefulness in the prevention of bacterial infection.

Bone Morphogenic Protein 2-Loaded Porous Silicon Carriers for Osteoinductive Implants

Bone morphogenetic proteins (BMPs) are probably the most important growth factors in bone formation and healing. However, the utilization of BMPs in clinical applications is mainly limited due to the protein poor solubility at physiological pH, rapid clearance and relatively short biological half-life. Herein, we develop degradable porous silicon (PSi)-based carriers for sustained delivery of BMP-2. Two different loading approaches are examined, physical adsorption and covalent conjugation, and their effect on the protein loading and release rate is thoroughly studied. The entrapment of the protein within the PSi nanostructures preserved its bioactivity for inducing osteogenic differentiation of rabbit bone marrow mesenchymal stems cells (BM-MSCs). BM-MSCs cultured with the BMP-2 loaded PSi carriers exhibit a relatively high alkaline phosphatase (ALP) activity. We also demonstrate that exposure of MSCs to empty PSi (no protein) carriers generates some extent of differentiation due to the ability of the carrier's degradation products to induce osteoblast differentiation. Finally, we demonstrate the integration of these promising BMP-2 carriers within a 3D-printed patient-specific implant, constructed of poly(caprolactone) (PCL), as a potential bone graft for critical size bone defects.

Advanced drug delivery systems and artificial skin grafts for skin wound healing

Cutaneous injuries, especially chronic wounds, burns, and skin wound infection, require painstakingly long-term treatment with an immense financial burden to healthcare systems worldwide. However, clinical management of chronic wounds remains unsatisfactory in many cases. Various strategies including growth factor and gene delivery as well as cell therapy have been used to enhance the healing of non-healing wounds. Drug delivery systems across the nano, micro, and macroscales can extend half-life, improve bioavailability, optimize pharmacokinetics, and decrease dosing frequency of drugs and genes. Replacement of the damaged skin tissue with substitutes comprising cell-laden scaffold can also restore the barrier and regulatory functions of skin at the wound site. This review covers comprehensively the advanced treatment strategies to improve the quality of wound healing.

Biofunctional Nanofibrous Substrate for Local TNF-Capturing as a Strategy to Control Inflammation in Arthritic Joints

Rheumatoid arthritis (RA) is an autoimmune disease that affects the synovial cavity of joints, and its pathogenesis is associated with an increased expression of pro-inflammatory cytokines, namely tumour necrosis factor-alpha (TNF-α). It has been clinically shown to have an adequate response to systemic administration of TNF-α inhibitors, although with many shortcomings. To overcome such limitations, the immobilization of a TNF-α antibody on a nanofibrous substrate to promote a localized action is herein proposed. By using this approach, the antibody has its maximum therapeutic efficacy and a prolonged therapeutic benefit, avoiding the systemic side-effects associated with conventional biological agents' therapies. To technically achieve such a purpose, the surface of electrospun nanofibers is initially activated and functionalized, allowing TNF-α antibody immobilization at a maximum concentration of 6 µg/mL. Experimental results evidence that the biofunctionalized nanofibrous substrate is effective in achieving a sustained capture of soluble TNF-α over time. Moreover, cell biology assays demonstrate that this system has no deleterious effect over human articular chondrocytes metabolism and activity. Therefore, the developed TNF-capturing system may represent a potential therapeutic approach for the local management of severely affected joints.

Porous Silicon as a Platform for Radiation Theranostics Together with a Novel RIB-Based Radiolanthanoid

Mesoporous silicon (PSi) is biocompatible and tailorable material with high potential in drug delivery applications. Here, we report of an evaluation of PSi as a carrier platform for theranostics by delivering a radioactive ion beam- (RIB-) based radioactive lanthanoid into tumors in a mouse model of prostate carcinoma. Thermally hydrocarbonized porous silicon (THCPSi) wafers were implanted with 159Dy at the facility for radioactive ion beams ISOLDE located at CERN, and the resulting [159Dy]THCPSi was postprocessed into particles. The particles were intratumorally injected into mice bearing prostate cancer xenografts. The stability of the particles was studied in vivo, followed by ex vivo biodistribution and autoradiographic studies. We showed that the process of producing radionuclide-implanted PSi particles is feasible and that the [159Dy]THCPSi particles stay stable and local inside the tumor over seven days. Upon release of 159Dy from the particles, the main site of accumulation is in the skeleton, which is in agreement with previous studies on the biodistribution of dysprosium. We conclude that THCPSi particles are a suitable platform together with RIB-based radiolanthanoids for theranostic purposes as they are retained after administration inside the tumor and the radiolanthanoid remains embedded in the THCPSi.

Photoluminescent and biodegradable porous silicon nanoparticles for biomedical imaging

A set of unique properties including biodegradability, intrinsic photoluminescence, and mesoporous structure allows porous silicon nanoparticles to address current challenges of translational nanomedicine, especially in biomedical imaging.

Tailoring Porous Silicon for Biomedical Applications: From Drug Delivery to Cancer Immunotherapy

In the past two decades, porous silicon (PSi) has attracted increasing attention for its potential biomedical applications. With its controllable geometry, tunable nanoporous structure, large pore volume/high specific surface area, and versatile surface chemistry, PSi shows significant advantages over conventional drug carriers. Here, an overview of recent progress in the use of PSi in drug delivery and cancer immunotherapy is presented. First, an overview of the fabrication of PSi with various geometric structures is provided, with particular focus on how the unique geometry of PSi facilitates its biomedical applications, especially for drug delivery. Second, surface chemistry and modification of PSi are discussed in relation to the strengthening of its performance in drug delivery and bioimaging. Emerging technologies for engineering PSi-based composites are then summarized. Emerging PSi advances in the context of cancer immunotherapy are also highlighted. Overall, very promising research results encourage further exploration of PSi for biomedical applications, particularly in drug delivery and cancer immunotherapy, and future translation of PSi into clinical applications.

Novel Gd-Loaded Silicon Nanohybrid: A Potential Epidermal Growth Factor Receptor Expressing Cancer Cell Targeting Magnetic Resonance Imaging Contrast Agent

Continuing our research efforts in developing mesoporous silicon nanoparticle-based biomaterials for cancer therapy, we employed here porous silicon nanoparticles as a nanocarrier to deliver contrast agents to diseased cells. Nanoconfinement of small molecule Gd-chelates (L1-Gd) enhanced the T₁ contrast dramatically compared to distinct Gd-chelate (L1-Gd) by virtue of its slow tumbling rate, increased number of bound water molecules, and their occupancy time. The newly synthesized Gd-chelate (L1-Gd) was covalently grafted on silicon nanostructures and conjugated to an antibody specific for epidermal growth factor receptor (EGFR) via a hydrazone linkage. The salient feature of this nanosized contrast agent is the capability of EGFR targeted delivery to cancer cells. Mesoporous silicon nanoparticles were chosen as the nanocarrier because of their high porosity, high surface area, and excellent biodegradability. This type of nanosized contrast agent also performs well in high magnetic fields.

Oral Mucosal Epithelial Cells Grown on Porous Silicon Membrane for Transfer to the Rat Eye

Dysfunction of limbal stem cells or their niche can result in painful, potentially sight-threatening ocular surface disease. We examined the utility of surface-modified porous-silicon (pSi) membranes as a scaffold for the transfer of oral mucosal cells to the eye. Male-origin rat oral mucosal epithelial cells were grown on pSi coated with collagen-IV and vitronectin, and characterised by immunocytochemistry. Scaffolds bearing cells were implanted into normal female rats, close to the limbus, for 8 weeks. Histology, immunohistochemistry and a multiplex nested PCR for sry were performed to detect transplanted cells. Oral mucosal epithelial cells expanded on pSi scaffolds expressed the corneal epithelial cell marker CK3/12. A large percentage of cells were p63+, indicative of proliferative potential, and a small proportion expressed ABCG2+, a putative stem cell marker. Cell-bearing scaffolds transferred to the eyes of live rats, were well tolerated, as assessed by endpoint histology. Immunohistochemistry for pan-cytokeratins demonstrated that transplanted epithelial cells were retained on the pSi membranes at 8 weeks post-implant, but were not detectable on the central cornea using PCR for sry. The pSi scaffolds supported and retained transplanted rat oral mucosal epithelial cells in vitro and in vivo and recapitulate some aspects of an artificial stem cell niche.

Drug-Porous Silicon Dual Luminescent System for Monitoring and Inhibition of Wound Infection

Wound monitoring and curing is of great importance in biomedical research. This work created a smart bandage that can simultaneously monitor and inhibit wound infection. The main components of the smart bandage are luminescent porous silicon (LuPSi) particles loaded with ciprofloxacin (CIP). This dual luminescent system can undergo accelerated fluorescent color change from red to blue upon the stimulation of reactive oxygen species (ROS) and elevated pH, which are main biomarkers in the infected wound. The mechanism behind the chemical-triggered fluorescent color change was studied in detail. In vitro experiment showed that the ratiometric fluorescent intensity (I_Red/I_Blue) of CIP-LuPSi particles decreased from 10 to 0.03 at pH 7.5 after 24 h, while the value deceased from 10 to 2.15 at pH 7.0. Strong correlation can be also found between the I_Red/I_Blue value and ROS concentration ranging from 0.1 to 10 mM. In addition, the oxidation of LuPSi also simultaneously triggered the release of CIP molecules, which exhibited bacterial inhibition activity. Therefore, the ratiometric fluorescent intensity change at red and blue channels can indicate not only the wound infection status but also the release of antibiotics. In vivo test proved that the smart bandage could distinguish infected wounds from acute wounds, just relying on the naked eyes or a cell phone camera. On the basis of the Si nanotechnology established in this work, theranostic wound care will be realized in future.

Non-invasive, in vitro analysis of islet insulin production enabled by an optical porous silicon biosensor

A label-free porous silicon (pSi) based, optical biosensor, using both an antibody and aptamer bioreceptor motif has been developed for the detection of insulin. Two parallel biosensors were designed and optimised independently, based on each bioreceptor. Both bioreceptors were covalently attached to a thermally hydrosilylated pSi surface though amide coupling, with unreacted surface area rendered stable and low fouling by incorporation of PEG moieties. The insulin detection ability of each biosensor was determined using interferometric reflectance spectroscopy, using a range of different media both with and without serum. Sensing performance was compared in terms of response value, response time and limit of detection (LOD) for each platform. In order to demonstrate the capability of the best performing biosensor to detect insulin from real samples, an in vitro investigation with the aptamer-modified surface was performed. This biosensor was exposed to buffer conditioned by glucose-stimulated human islets, with the result showing a positive response and a high degree of selectivity towards insulin capture. The obtained results correlated well with the ELISA used in the clinic for assaying glucose-stimulated insulin release from donor islets. We anticipate that this type of sensor can be applied as a rapid point-of-use biosensor to assess the quality of donor islets in terms of their insulin production efficiency, prior to transplantation.

Delivery of Flightless I Neutralizing Antibody from Porous Silicon Nanoparticles Improves Wound Healing in Diabetic Mice

Flightless I (Flii) is elevated in human chronic wounds and is a negative regulator of wound repair. Decreasing its activity improves healing responses. Flii neutralizing antibodies (FnAbs) decrease Flii activity in vivo and hold significant promise as healing agents. However, to avoid the need for repeated application in a clinical setting and to protect the therapeutic antibody from the hostile environment of the wound, suitable delivery vehicles are required. In this study, the use of porous silicon nanoparticles (pSi NPs) is demonstrated for the controlled release of FnAb to diabetic wounds. We achieve FnAb loading regimens exceeding 250 µg antibody per mg of vehicle. FnAb-loaded pSi NPs increase keratinocyte proliferation and enhance migration in scratch wound assays. Release studies confirm the functionality of the FnAb in terms of Flii binding. Using a streptozotocin-induced model of diabetic wound healing, a significant improvement in healing is observed for mice treated with FnAb-loaded pSi NPs compared to controls, including FnAb alone. FnAb-loaded pSi NPs treated with proteases show intact and functional antibody for up to 7 d post-treatment, suggesting protection of the antibodies from proteolytic degradation in wound fluid. pSi NPs may therefore enable new therapeutic approaches for the treatment of diabetic ulcers.

Porous Silicon-Based Cell Microarrays: Optimizing Human Endothelial Cell-Material Surface Interactions and Bioactive Release

Porous silicon (pSi) substrates are a promising platform for cell expansion, since pore size and chemistry can be tuned to control cell behavior. In addition, a variety of bioactives can be loaded into the pores and subsequently released to act on cells adherent to the substrate. Here, we construct a cell microarray on a plasma polymer coated pSi substrate that enables the simultaneous culture of human endothelial cells on printed immobilized protein factors, while a second soluble growth factor is released from the same substrate. This allows three elements of candidate pSi scaffold materials-topography, surface functionalization, and controlled factor release-to be assessed simultaneously in high throughput. We show that protein conjugation within printed microarray spots is more uniform on the pSi substrate than on flat glass or silicon surfaces. Active growth factors are released from the pSi surface over a period of several days. Using an endothelial progenitor cell line, we investigate changes in cell behavior in response to the microenvironment. This platform facilitates the design of advanced functional biomaterials, including scaffolds, and carriers for regenerative medicine and cell therapy.

"Thunderstruck": Plasma-Polymer-Coated Porous Silicon Microparticles As a Controlled Drug Delivery System

Controlling the release kinetics from a drug carrier is crucial to maintain a drug's therapeutic window. We report the use of biodegradable porous silicon microparticles (pSi MPs) loaded with the anticancer drug camphothecin, followed by a plasma polymer overcoating using a loudspeaker plasma reactor. Homogenous "Teflon-like" coatings were achieved by tumbling the particles by playing AC/DC's song "Thunderstruck". The overcoating resulted in a markedly slower release of the cytotoxic drug, and this effect correlated positively with the plasma polymer coating times, ranging from 2-fold up to more than 100-fold. Ultimately, upon characterizing and verifying pSi MP production, loading, and coating with analytical methods such as time-of-flight secondary ion mass spectrometry, scanning electron microscopy, thermal gravimetry, water contact angle measurements, and fluorescence microscopy, human neuroblastoma cells were challenged with pSi MPs in an in vitro assay, revealing a significant time delay in cell death onset.

Multi-dimensional on-particle detection technology for multi-category disease classification

Multidimensional on-particle detection technology expands the capacity of serum peptide information and reveals disease biomarkers for future clinical diagnosis.