Porous Silicon Microparticles Research Articles

Dynamic magnesiothermic reduction of various silica to porous silicon structures for lithium battery anodes

A dynamic magnesiothermic reduction (DMR) of various silica having different size and porosity is conducted to study the effects of silica properties on the ⅰ) DMR reaction kinetics, ⅱ) properties of resulting porous silicon (pSi) microparticles, and ⅲ) performances of pSi/C composites as anodes in lithium batteries. A DMR kinetic study using the Ginstling–Brounstein diffusion model shows that the smaller the silica particle size, the higher the reduction rate and the lower the apparent activation energy. Irrespective of silica properties, all the resulting pSi particles have mesoporous structures. The pSi particles comprise interconnected small primary silicon nanoparticles (approximately 30–40 nm in diameter) to render similar particle morphologies to those of the parent silica. Owing to these appealing features of pSi particles, pSi/C composites exhibit excellent cycling performance for over 200 cycles and high rate capabilities, whereas SiMP/C (prepared with a non-porous silicon microparticles) loses most of its capacity in early cycles owing to high resistance build-up during cycling. Overall, the DMR of silica precursors of several micrometers or less in size (preferably porous precursors) are desirable for the production of high-purity pSi microparticles for use in high-capacity and stable anodes for advanced lithium batteries.

Porous silicon microparticles as efficient carriers for immunologic adjuvants

In this work we report a first-time combination of porous silicon (pSi) particles with the immunologic adjuvant Pam3CSK4, a TLR 1/2 agonist, as a tool for immunotherapy. pSi is a sponge-like biocompatible and biodegradable nanomaterial with high porosity, large surface-to-volume ratio and tunable surface, suitable for drug delivery applications. This study provides, by means of live-cell confocal microscopy, an insight about the time course of the interaction of free Pam3CSK4 vs vectorized by pSi microparticles with human dendritic cells (DCs). We found a delay in the ingestion of the agonist when carried by pSi microparticles. These findings were supported by the observation of the morphological changes related to the activation of DCs that occurred with a 5 h difference when treated with the vectorized ligand.These results provide the first demonstration of pSi as a conceivable candidate to deliver Pam3CSK4 to DCs paving the way towards immunotherapy practice.

Biolistic Delivery of Photosensitizer‐Loaded Porous Si Carriers for Localized Photodynamic Therapy

AbstractAmong numerous approaches for treating cancer, clinically approved photodynamic therapy (PDT) is considered a promising non‐invasive therapeutic strategy for solid tumors. While PDT has distinct advantages over conventional cancer treatments, systemic exposure to the photosensitizer and its stability are some of the limitations of clinical PDT. Herein, a therapeutic strategy for highly localized focal PDT is introduced based on direct biolistic delivery of photosensitizer‐loaded carriers to cancerous tumors. Degradable porous silicon microparticles (PSiMPs) are used as efficient carriers for the photosensitizer, meso‐tetrahydroxy‐phenylchlorin (mTHPC), and its conjugates with gold nanoparticles (AuNP‐mTHPC conjugates). The loaded PSiMP carriers are successfully bombarded using a pneumatic gene gun to breast cancer cells in vitro and into tumor xenografts in vivo, and subsequent uptake of the released photosensitizer payload is demonstrated. PDT irradiation is commenced after 24 h based on the release profile, resulting in complete cell death in vitro and substantial inhibition of tumor growth in vivo. Notably, using empty PSiMP carriers also leads to some tumor growth inhibition, ascribing to its intrinsic photosensitizing activity. Treatment with AuNP‐mTHPC‐loaded PSiMPs exhibits a superior therapeutic effect in comparison to bombarded mTHPC‐loaded carriers and administration of free mTHPC. This biolistic delivery scheme may be advantageous for precision photodynamic therapy.

Reduction kinetics of porous silicon synthesis for lithium battery anodes

Porous silicon (pSi) microparticles can be favorably employed as the high-capacity and stable anode materials in all formats of lithium-based batteries. Magnesiothermic reduction reaction (MRR) of low-cost silica produces pSi structures at relatively low temperatures; however, yield and reduction selectivity are currently limited. Herein, we conduct MRR kinetic studies using the Ginstling–Brounstein (GB) and Jander diffusion models under dynamic (via reactor rotation) and static conditions (D-MRR and S-MRR, respectively) at various reduction temperatures and times. The reduction rate and nominal kinetic constants for the d-MRR are found to be more than three times greater than those for the S-MRR, possibly because of the enhanced mass transfer rate in the d-MRR. d-MRR results in superior precursor conversion and pSi yield than S-MRR. The apparent activation energy for d-MRR is approximately 180 kJ mol–1 by GB model. The pSi microparticles are mesoporous (pore size = 23.7 nm, pore volume = 0.30 cm3 g–1) and comprise interconnected primary silicon nanoparticles (SiNPs) (diameter = 30 nm). Therefore, a pSi/C composite anode demonstrates significantly enhanced cycling stability compared with conventional solid SiNP/C composites. Overall, d-MRR is a highly efficient and scalable production process for pSi microparticles for use in high-capacity anodes for advanced lithium-based batteries.

Integration of metabolomics and peptidomics reveals distinct molecular landscape of human diabetic kidney disease.

Diabetic kidney disease (DKD) is the most common microvascular complication of diabetes, and there is an urgent need to discover reliable biomarkers for early diagnosis. Here, we established an effective urine multi-omics platform and integrated metabolomics and peptidomics to investigate the biological changes during DKD pathogenesis. Methods: Totally 766 volunteers (221 HC, 198 T2DM, 175 early DKD, 125 overt DKD, and 47 grey-zone T2DM patients with abnormal urinary mALB concentration) were included in this study. Non-targeted metabolic fingerprints of urine samples were acquired on matrix-free LDI-MS platform by the tip-contact extraction method using fluorinated ethylene propylene coated silicon nanowires chips (FEP@SiNWs), while peptide profiles hidden in urine samples were uncovered by MALDI-TOF MS after capturing urine peptides by porous silicon microparticles. Results: After multivariate analysis, ten metabolites and six peptides were verified to be stepwise regulated in different DKD stages. The altered metabolic pathways and biological processes associated with the DKD pathogenesis were concentrated in amino acid metabolism and cellular protein metabolic process, which were supported by renal transcriptomics. Interestingly, multi-omics significantly increased the diagnostic accuracy for both early DKD diagnosis and DKD status discrimination. Combined with machine learning, a stepwise prediction model was constructed and 89.9% of HC, 75.5% of T2DM, 69.6% of early DKD and 75.7% of overt DKD subjects in the external validation cohort were correctly classified. In addition, 87.5% of grey-zone patients were successfully distinguished from T2DM patients. Conclusion: This multi-omics platform displayed a satisfactory ability to explore molecular information and provided a new insight for establishing effective DKD management.

Breast cancer vaccines: New insights into immunomodulatory and nano-therapeutic approaches.

Breast cancer (BC) is known to be a highly heterogeneous disease that is clinically subdivided into four primary molecular subtypes, each having distinct morphology and clinical implications. These subtypes are principally defined by hormone receptors and other proteins involved (or not involved) in BC development. BC therapeutic vaccines [including peptide-based vaccines, protein-based vaccines, nucleic acid-based vaccines (DNA/RNA vaccines), bacterial/viral-based vaccines, and different immune cell-based vaccines] have emerged as an appealing class of cancer immunotherapeutics when used alone or combined with other immunotherapies. Employing the immune system to eliminate BC cells is a novel therapeutic modality. The benefit of active immunotherapies is that they develop protection against neoplastic tissue and readjust the immune system to an anti-tumor monitoring state. Such immunovaccines have not yet shown effectiveness for BC treatment in clinical trials. In recent years, nanomedicines have opened new windows to increase the effectiveness of vaccinations to treat BC. In this context, some nanoplatforms have been designed to efficiently deliver molecular, cellular, or subcellular vaccines to BC cells, increasing the efficacy and persistence of anti-tumor immunity while minimizing undesirable side effects. Immunostimulatory nano-adjuvants, liposomal-based vaccines, polymeric vaccines, virus-like particles, lipid/calcium/phosphate nanoparticles, chitosan-derived nanostructures, porous silicon microparticles, and selenium nanoparticles are among the newly designed nanostructures that have been used to facilitate antigen internalization and presentation by antigen-presenting cells, increase antigen stability, enhance vaccine antigenicity and remedial effectivity, promote antigen escape from the endosome, improve cytotoxic T lymphocyte responses, and produce humoral immune responses in BC cells. Here, we summarized the existing subtypes of BC and shed light on immunomodulatory and nano-therapeutic strategies for BC vaccination. Finally, we reviewed ongoing clinical trials on BC vaccination and highlighted near-term opportunities for moving forward.

Trans-Cinnamaldehyde Eluting Porous Silicon Microparticles Mitigate Cariogenic Biofilms

Dental caries, a preventable disease, is caused by highly-adherent, acid-producing biofilms composed of bacteria and yeasts. Current caries-preventive approaches are ineffective in controlling biofilm development. Recent studies demonstrate definite advantages in using natural compounds such as trans-cinnamaldehyde in thwarting biofilm assembly, and yet, the remarkable difficulty in delivering such hydrophobic bioactive molecules prevents further development. To address this critical challenge, we have developed an innovative platform composed of components with a proven track record of safety. We fabricated and thoroughly characterised porous silicon (pSi) microparticles to carry and deliver the natural phenyl propanoid trans-cinnamaldehyde (TC). We investigated its effects on preventing the development of cross-kingdom biofilms (Streptococcus mutans and Candida albicans), typical of dental caries found in children. The prepared pSi microparticles were roughly cubic in structure with 70–75% porosity, to which the TC (pSi-TC) was loaded with about 45% efficiency. The pSi-TC particles exhibited a controlled release of the cargo over a 14-day period. Notably, pSi-TC significantly inhibited biofilms, specifically downregulating the glucan synthesis pathways, leading to reduced adhesion to the substrate. Acid production, a vital virulent trait for caries development, was also hindered by pSi-TC. This pioneering study highlights the potential to develop the novel pSi-TC as a dental caries-preventive material.

Synthesis of carbon nanotubes-supported porous silicon microparticles in low-temperature molten salt for high-performance Li-ion battery anodes

Synthesis of carbon nanotubes-supported porous silicon microparticles in low-temperature molten salt for high-performance Li-ion battery anodes

Development of self-microemulsifying tablets containing dutasteride for enhanced dissolution and pharmacokinetic profile

This study aimed to develop self-microemulsifying tablets containing the hydrophobic drug dutasteride for easy administration and high in vivo absorption. The candidate lipids and surfactants were formulated into a self-microemulsifying drug delivery system (SMEDDS), and their mean droplet size upon dilution was evaluated. The SMEDDS containing Capmul® MCM, Captex® 355, and Cremophor® EL showed improved dissolution in the gastric medium when compared to the dissolution of the conventional product (Avodart®) and the raw drug. Among the various porous silicon microparticles for solidifying SMEDDS, Neusilin® US2 showed favorable properties in terms of maximum adsorption capacity, powder flow, and compaction. However, the amount of drug released from the solidified SMEDDS after the adsorption process was lower than that of liquid SMEDDS, indicating incomplete desorption. After observing the effect of the solid-to-liquid ratio and pre-filling the pores with blank SMEDDS, complete desorption was obtained when the pores were first adsorbed with polyvinylpyrrolidone. The self-microemulsifying tablets exhibited improved bioavailability (29.9% and 15.2%) compared to the conventional soft gelatin product. Therefore, the proposed system could successfully solubilize the hydrophobic drug while maintaining rapid and complete desorption from the solid carrier, resulting in enhanced in vivo performance.

Rad51 Silencing with siRNA Delivered by Porous Silicon-Based Microparticle Enhances the Anti-Cancer Effect of Doxorubicin in Triple-Negative Breast Cancer

Due to its high heterogeneity and aggressiveness, cytotoxic chemotherapy is still a mainstay treatment for triple negative breast cancer. Unfortunately, the above mentioned has not significantly ameliorated TNBC patients and induces drug resistance. Exploring the mechanisms underlying the chemotherapy sensitivity of TNBC and developing novel sensitization strategies are promising approaches for improving the prognosis of patients. Rad51, a key regulator of DNA damage response pathway, repairs DNA damage caused by genotoxic agents through "homologous recombination repair." Therefore, Rad51 inhibition may increase TNBC cell sensitivity to anticancer agents. Based on these findings, we first designed Rad51 siRNA to inhibit the Rad51 protein expression in vitro and evaluated the sensitivity of TNBC cells to doxorubicin. Subsequently, we constructed discoidal porous silicon microparticles (pSi) and encapsulated discoidal 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes/siRad51 (PS-DOPC/siRad51) to explore the synergistic antitumor effects of siRad51 and doxorubicin on two mouse models of TNBC in vivo. Our in vitro studies indicated that siRad51 enhanced the efficacy of DOX chemotherapy and significantly suppressed TNBC cell proliferation and metastasis. This effect was related to apoptosis induction and epithelial to mesenchymal transition (EMT) inhibition. siRad51 altered the expression of apoptosis- and EMT-related proteins. In orthotopic and lung metastasis xenograft models, the administration of PS-DOPC/siRad51 in combination with DOX significantly alleviated the primary tumor burden and lung metastasis, respectively. Our current studies present an efficient strategy to surmount chemotherapy resistance in TNBC through microvector delivery of siRad51.

Synergistic and On-Demand Release of Ag-AMPs Loaded on Porous Silicon Nanocarriers for Antibacteria and Wound Healing.

Due to the abuse of antibiotics, antimicrobial resistance is rapidly emerging and becoming a major global risk for public health. Thus, there is an urgent need for reducing the use of antibiotics, finding novel treatment approaches, and developing controllable release systems. In this work, a dual synergistic antibacterial platform with on-demand release ability based on silver nanoparticles (AgNPs) and antimicrobial peptide (AMP) coloaded porous silicon (PSi) was developed. The combination of AgNPs and AMPs (Tet-213, KRWWKWWRRC) exhibited an excellent synergistic antibacterial effect. As a carrier, porous silicon can efficiently load AgNPs and AMP under mild conditions and give the platform an on-demand release ability and a synergistic release effect. The AgNPs and AMP coloaded porous silicon microparticles (AgNPs-AMP@PSiMPs) exhibited an acid pH and reactive oxygen species (ROS)-stimulated release of silver ions (Ag+) and AMPs under bacterial infection conditions because of oxidation and desorption effects. Moreover, the release of the bactericide could be promoted by each other due to the interplay between AgNPs and Tet-213. In vitro antibacterial tests demonstrated that AgNPs-AMP@PSiMPs inherited the intrinsic properties and synergistic antibacterial efficiency of both bactericides. In addition, wound dressing loaded with AgNPs-AMP@PSiMPs showed outstanding in vivo bacteria-killing activity, accelerating wound-healing, and low biotoxicity in aStaphylococcus aureus-infected rat wound model. The present work demonstrated that PSiMPS might be an efficient platform for loading the antibiotic-free bactericide, which could synergistically and on-demand release to fight wound infection and promote wound healing.

A co-delivery platform for synergistic promotion of angiogenesis based on biodegradable, therapeutic and self-reporting luminescent porous silicon microparticles

Insufficient angiogenesis happened in body defects such as ulceration, coronary heart disease, and chronic wounds constitutes a major challenge in tissue regeneration engineering. Owing to the poor bioactivity and maintenance of pro-angiogenic cells and factors during transplantation, new bioactive materials to tackle the barrier are highly desirable. Herein, we demonstrate a co-delivery platform for synergistic promotion of angiogenesis based on biodegradable, therapeutic, and self-reporting luminescent porous silicon (PSi) microparticles. The biodegradable and biocompatible PSi microparticles could quickly release therapeutic Si ions, which is bioactive to promote cell migration, tube formation, and angiogenic gene expression in vitro. To construct a highly efficient angiogenesis treatment platform, vascular endothelial growth factor (VEGF) was electrostatically adsorbed by PSi microparticles for effective drug loading and delivery. The dual therapeutic components (Si ions and VEGF) could release with the dissolution of Si skeleton, accompanying by the decay of photoluminescence (PL) intensity and blue shift of the maximum PL wavelength. Therefore, real-time drug release could be self-reported and assessed with the two-dimensional PL signal. The co-delivery of Si ions and VEGF displayed synergistic effect and highly efficient angiogenesis, which was evidenced by the enhancement of endothelial cell migration and tube formation in vitro with approximately 1.5–5 times higher than control. The blood vessel formation in vivo was also significantly improved as shown by the chick chorioallantoic membrane (CAM) model, in which the total length, size and junctions exhibited 2.1 ± 0.4, 4 ± 0.4, and 3.9 ± 0.3 times in comparison to control, respectively. The PSi and VEGF co-delivery system display great potential in tissue engineering as a biodegradable and self-reporting theranostic platform to promote angiogenesis.

Enhancement of both optical and catalytic activity of copper-decorated porous silicon micro-particles

To the best of our knowledge, this study is the first to investigate the effect of chemical vapour etching (CVE) combined with copper decoration on both the optical and catalytic activities of silicon micro-particles (SiμPs). After exposure to acid vapours emanating from a hot solution of hydrogen fluoride/nitric acid (HF/HNO3), scanning electron microscope images of the treated powder show the formation of a porous, sponge-like structure on the sidewalls of SiμPs. Fourier transmission infra-red analysis shows the appearance of hydride bonds related to the formation of the porous structure. X-ray diffraction measurements and Raman spectroscopy show the good crystallinity of the samples. The strong photoluminescence properties of the obtained porous SiμPs (pSiμPs) reveal that the vapour etching process generated silicon nanocrystals within these particles. In this work, we have investigated the catalytic activity of copper nanoparticles (CuNPs) loaded on the surface of pSiμPs, in order to reduce the toxic compound 4-nitrophenol to 4-aminophenol. The results show excellent catalytic performance in very short times (less than 1 min).

Cytotoxicity of Mitomycin C-Porous Silicon in Human Prostate Carcinoma Cells

Porous silicon (pSi) microparticles with pore diameter 15 to 20 nm were fabricated by electrochemical etching of single-crystalline silicon (Si) wafers (n-type) to be used as delivery systems for the anticancer drug mitomycin C (MMC). The in vitro toxicity of the mitomycin-loaded pSi carrier was investigated on human prostate carcinoma (DU145) cells. The cells showed a decrease in viability of ~80% over a 6 hours period, when using mitomycin. Meanwhile, a ~55% decrease in cell viability was observed, when using the pSi carrier to deliver the drug. The drug-loaded carrier showed a sustained release throughout 24 hours, with an 80% decrease in cell viability after 16 hours. This observed controlled release of mitomycin from the pSi carrier suggests a superior therapeutic effect than the direct administration of mitomycin, as it potentially minimizes the drug side effects. Results showed that the strong cytotoxic effect towards the prostate cancer cells was due to the drug and not the carrier since the mitomycin-loaded pSi carrier affected cell viability, but the pSi carrier showed no toxicity. Furthermore, it was observed that with a higher amount of drug-loaded carriers, the toxicity effect was higher, thus, allowing further control of the therapeutic effect of the carrier.

Hybrid Composite of Silver Nanoparticle-Porous Silicon Microparticles as an Image-Guided Localization Agent for Computed Tomography Scan of the Lungs.

A hybrid composite of silver nanoparticles (AgNPs) and porous silicon microparticles (pSiMPs) was developed and applied for the computed tomography (CT) scanning of the lungs as an image-guided localization agent. We confirmed the grafting of AgNPs on oxidized pSiMPs template using various analytical equipment, including a scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The hybrid composite showed a high CT contrast intensity (>1000 HU) that enabled us to produce and view images of the lungs. In addition, it showed the ability to maintain a strong CT signal at the injected area of the rabbit's lungs, up to an hour, without spreading. The lack of toxicity and immune response indicated that the composite could be fully utilized as a new image-guided localization agent of CT scans for lung cancer surgery.

Loading and Controlled Release of Poorly Water-Soluble Drug Telmisartan from Porous Silicon Microparticles

To prepare porous silicon microparticles by electrochemical etching process and study telmisartan loading and release kinetics to develop controlled drug delivery system. A 50 mA/cm2 of current density was applied for 180 s in HF:ethanol (2:4) solution for the etching of silicon wafer. The silicon film was fractured by probe sonication at 20 kHz of frequency and 750 W powers for 120 s to make the micro-sized particles. Drug-loading was carried out by taking 1 M sodium hydroxides solution and in vitro release of telmisartan was investigated using various models, such as zero order, first order, Hixson Crowell, Korsmeyer-Peppas, and Higuchi diffusion model. A telmisartan loaded native porous silicon microparticles (TEL-PSi) allowed a very high drug loading up to 58.39 micrograms as compared to telmisartan loaded thermally oxidized porous silicon (TEL-TOPSi) (28.14 micrograms). TEL-TOPSi showed controlled release as compare to TEL-PSi. The release rate of TEL-TOPSi and TEL-PSi was 47% and 77% after 5 h respectively. The Korsmeyer-Peppas model was selected based on its excellent fitting to the release data among all models and indicates diffusion-based release. Telmisartan loading and its release kinetics was studied successfully on porous silicon micro particles. TEL-TOPSi micro particles can be used for controlled drug delivery system for poorly water-soluble active pharmaceutical ingredients.

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.

Structural Analysis of Nanoparticles Formed via Laser Ablation of Porous Silicon and Silicon Microparticles in Water

Silicon nanoparticles with sizes of 50–300 nm have been formed via picosecond laser ablation of porous silicon and silicon microparticles in water using various targets. Raman spectroscopy has revealed the presence of a low amount of the amorphous phase in the obtained particles (10–12%) prepared from micro- and mesoporous silicon layers and almost a zero degree of crystallinity in the case of laser fragmentation of silicon micropowders in water. The results are promising for further application of the nanoparticles in photonics and biomedicine.

Plant-Derived Tandem Drug/Mesoporous Silicon Microcarrier Structures for Anti-Inflammatory Therapy.

The properties of nanostructured plant-derived porous silicon (pSi) microparticles as potential candidates to increase the bioavailability of plant extracts possessing anti-inflammatory activity are described in this work. pSi drug carriers were fabricated using an eco-friendly route from the silicon accumulator plant bamboo (tabasheer) powder by magnesiothermic reduction of plant-derived silica and loaded with ethanolic extracts of Equisetum arvense, another silicon accumulator plant rich in polyphenolic compounds. The anti-inflammatory properties of the active therapeutics present in this extract were measured by sensitive luciferase reporter assays; this active extract was subsequently loaded and released from the pSi matrix, with a clear inhibition of the activity of the inflammatory signaling protein NF-κB over a period of hours in a sustained manner. Our results showed that after loading the extracts of E. arvense into pSi microparticles derived from tabasheer, enhanced anti-inflammatory activity was observed owing to enhanced solubility of the extract.

Ultrasonication effect on size distribution of functionalized porous silicon microparticles

Sponge-like luminescent mesoporous silicon microparticles are produced from crystalline silicon with a simple and cheap top-down fabrication process which, however, offers scarce control of structural features such size, size distribution and pore dimensions of the final product. Herein, we report on a post-fabrication procedure based on ultrasonic treatment to get more homogeneous size distribution and much more control on the average dimension of the microparticles. We investigated the effect of variable ultrasonic treatments on the structural and optical properties of the microparticles. The structure was analysed both at micro and nano scale and for microparticles in dried state and in solution. We proved that few minutes of sonication strongly limits the heterogeneity of the sample size, without affecting the optical properties and porous structure. This simple post-fabrication step offers new opportunities for successful use of silicon microparticles in biomedicine.