Special Issue "Porous Silicon for Drug Delivery"

A special issue of Pharmaceutics (ISSN 1999-4923).

Deadline for manuscript submissions: closed (30 September 2019).

Special Issue Editor

Dr. Luis M. Bimbo
E-Mail Website
Guest Editor
Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, G4 0RE, Glasgow, United Kingdom
Interests: porous materials; pharmaceutical processing; drug nanocrystals; lung delivery

Special Issue Information

Dear Colleagues,

Porous silicon is an outstandingly versatile material due to its excellent mechanical, thermal, and photonic properties, and is currently being explored in fields so dissimilar such optoelectronics, gas sensing, energy storage, and biotechnology. Although the material was first reported in the mid-1950s, it took over 30 years to attract significant interest in the biomedical field. This newfound interest was especially due to the discovery of porous silicon’s bioactive nature and biodegradability. Porous silicon’s large pore volume, together with its large surface area, have also enabled this structure to act as a reservoir for loading a wide array of different compounds of interest, via selective tailoring of size and surface chemistries of the pores. The confinement of drugs within macro and mesopores heralded new ways to modulate the molecules’ thermodyamic arrangements and led to new insights into crystallization and amorphisation processes, which are critical for the material’s pharmaceutical processability. Many pharmaceutical applications are further expanded by porous silicon’s intrinsic luminescence, which originates from quantum confinement effects, together with the ease of labelling of its surface with radiotracers and fluorescent molecules for theranostics and imaging purposes.

This Special Issue focuses on recent developments in the area of drug delivery using porous silicon in its many aspects, covering emerging pharmaceutically acceptable routes of synthesis for the material, as well as functionalisation strategies for its surface. Challenges in its clinical translation and pharmaceutical processability will also be discussed, together with opportunities and current commercialisation efforts.

Dr. Luis M. Bimbo
Guest Editor

Manuscript Submission Information

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Keywords

  • Biogenic sources of silicon for drug delivery applications
  • Porous silicon as an imaging platform for biomedical purposes
  • Biofunctionalisation of porous silicon vectors
  • Multistage porous silicon formulations
  • Pharmaceutical processing of porous silicon particles
  • High aspect-ratio porous silicon structures for the sensing and delivery of therapeutics
  • Porous silicon-based biosensors and their therapeutic applications

Published Papers (7 papers)

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Research

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Open AccessArticle
Site-Specific 111In-Radiolabeling of Dual-PEGylated Porous Silicon Nanoparticles and Their In Vivo Evaluation in Murine 4T1 Breast Cancer Model
Pharmaceutics 2019, 11(12), 686; https://doi.org/10.3390/pharmaceutics11120686 - 17 Dec 2019
Cited by 1 | Viewed by 871
Abstract
Polyethylene glycol (PEG) has been successfully used for improving circulation time of several nanomaterials but prolonging the circulation of porous silicon nanoparticles (PSi NPs) has remained challenging. Here, we report a site specific radiolabeling of dual-PEGylated thermally oxidized porous silicon (DPEG-TOPSi) NPs and [...] Read more.
Polyethylene glycol (PEG) has been successfully used for improving circulation time of several nanomaterials but prolonging the circulation of porous silicon nanoparticles (PSi NPs) has remained challenging. Here, we report a site specific radiolabeling of dual-PEGylated thermally oxidized porous silicon (DPEG-TOPSi) NPs and investigation of influence of the PEGylation on blood circulation time of TOPSi NPs. Trans-cyclooctene conjugated DPEG-TOPSi NPs were radiolabeled through a click reaction with [111In]In-DOTA-PEG4-tetrazine (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) and the particle behavior was evaluated in vivo in Balb/c mice bearing 4T1 murine breast cancer allografts. The dual-PEGylation significantly prolonged circulation of [111In]In-DPEG-TOPSi particles when compared to non-PEGylated control particles, yielding 10.8 ± 1.7% of the injected activity/g in blood at 15 min for [111In]In-DPEG-TOPSi NPs. The improved circulation time will be beneficial for the accumulation of targeted DPEG-TOPSi to tumors. Full article
(This article belongs to the Special Issue Porous Silicon for Drug Delivery)
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Open AccessArticle
Controlling and Predicting the Dissolution Kinetics of Thermally Oxidised Mesoporous Silicon Particles: Towards Improved Drug Delivery
Pharmaceutics 2019, 11(12), 634; https://doi.org/10.3390/pharmaceutics11120634 - 28 Nov 2019
Cited by 1 | Viewed by 804
Abstract
Porous silicon (pSi) continues to receive considerable interest for use in applications ranging from sensors, biological scaffolds, therapeutic delivery systems to theranostics. Critical to all of these applications is pSi degradation and stabilization in biological media. Here we report on progress towards the [...] Read more.
Porous silicon (pSi) continues to receive considerable interest for use in applications ranging from sensors, biological scaffolds, therapeutic delivery systems to theranostics. Critical to all of these applications is pSi degradation and stabilization in biological media. Here we report on progress towards the development of a mechanistic understanding for the dissolution behavior of native (unoxidized) and thermally oxidized (200–600 °C) pSi microparticles. Fourier transform infrared (FTIR) spectroscopy was used to characterize the pSi surface chemistry after thermal oxidation. PSi dissolution was assessed using a USP method II apparatus by monitoring the production of orthosilicic acid, and the influence of gastro-intestinal (GI) fluids were examined. Fitting pSi dissolution kinetics with a sum of the exponential model demonstrated that the dissolution process strongly correlates with the three surface hydride species and their relative reactivity, and was supported by the observed FTIR spectral changes of pSi during dissolution. Finally, the presence of GI proteins was shown to hamper pSi dissolution by adsorption to the pSi surface acting as a barrier preventing water attack. These findings are significant in the optimal design of pSi particles for oral delivery and other controlled drug delivery applications. Full article
(This article belongs to the Special Issue Porous Silicon for Drug Delivery)
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Open AccessArticle
Bone Morphogenic Protein 2-Loaded Porous Silicon Carriers for Osteoinductive Implants
Pharmaceutics 2019, 11(11), 602; https://doi.org/10.3390/pharmaceutics11110602 - 12 Nov 2019
Cited by 5 | Viewed by 1211
Abstract
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. [...] Read more.
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. Full article
(This article belongs to the Special Issue Porous Silicon for Drug Delivery)
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Open AccessArticle
Folic Acid and PEI Modified Mesoporous Silica for Targeted Delivery of Curcumin
Pharmaceutics 2019, 11(9), 430; https://doi.org/10.3390/pharmaceutics11090430 - 23 Aug 2019
Cited by 15 | Viewed by 1623
Abstract
Nano anti-cancer drug carriers loaded with antineoplastic drugs can achieve targeted drug delivery, which enriches drugs at tumor sites and reduces the toxic side effects in normal tissues. Mesoporous silica nanoparticles (MSN) are good nano drug carriers, as they have large specific surface [...] Read more.
Nano anti-cancer drug carriers loaded with antineoplastic drugs can achieve targeted drug delivery, which enriches drugs at tumor sites and reduces the toxic side effects in normal tissues. Mesoporous silica nanoparticles (MSN) are good nano drug carriers, as they have large specific surface areas, adjustable pore sizes, easily modifiable surfaces, and good biocompatibility. In this work, polyethyleneimine (PEI) grafted MSN were modified with folic acid (FA) as an active target molecule using chemical methods. The product was characterized by SEM, TEM, Zetasizer nano, FTIR, and an N2 adsorption and desorption test. MSN-PEI-FA are porous nano particles with an average particle size of approximately 100 nm. In addition, the loading rate and release behavior of MSN-PEI-FA were studied with curcumin as a model drug. The results show that when loading curcumin to MSN-PEI-FA at 7 mg and 0.1 g, respectively, the encapsulation efficiency was 90% and the cumulative release rate reached more than 50% within 120 h at pH = 5. This drug delivery system is suitable for loading fat-soluble antineoplastic drugs for sustained release and pH sensitive delivery. Full article
(This article belongs to the Special Issue Porous Silicon for Drug Delivery)
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Review

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Open AccessReview
Crystallisation Behaviour of Pharmaceutical Compounds Confined within Mesoporous Silicon
Pharmaceutics 2020, 12(3), 214; https://doi.org/10.3390/pharmaceutics12030214 - 02 Mar 2020
Cited by 7 | Viewed by 929
Abstract
The poor aqueous solubility of new and existing drug compounds represents a significant challenge in pharmaceutical development, with numerous strategies currently being pursued to address this issue. Amorphous solids lack the repeating array of atoms in the structure and present greater free energy [...] Read more.
The poor aqueous solubility of new and existing drug compounds represents a significant challenge in pharmaceutical development, with numerous strategies currently being pursued to address this issue. Amorphous solids lack the repeating array of atoms in the structure and present greater free energy than their crystalline counterparts, which in turn enhances the solubility of the compound. The loading of drug compounds into porous materials has been described as a promising approach for the stabilisation of the amorphous state but is dependent on many factors, including pore size and surface chemistry of the substrate material. This review looks at the applications of mesoporous materials in the confinement of pharmaceutical compounds to increase their dissolution rate or modify their release and the influence of varying pore size to crystallise metastable polymorphs. We focus our attention on mesoporous silicon, due to the ability of its surface to be easily modified, enabling it to be stabilised and functionalised for the loading of various drug compounds. The use of neutron and synchrotron X-ray to examine compounds and the mesoporous materials in which they are confined is also discussed, moving away from the conventional analysis methods. Full article
(This article belongs to the Special Issue Porous Silicon for Drug Delivery)
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Open AccessReview
Silicon Nanotubes as Potential Therapeutic Platforms
Pharmaceutics 2019, 11(11), 571; https://doi.org/10.3390/pharmaceutics11110571 - 01 Nov 2019
Cited by 2 | Viewed by 871
Abstract
Silicon nanotubes (SiNTs) with unique well-defined structural morphologies have been successfully fabricated and recognized as a novel architecture in the nanoscale Si family. While the typical dendritic microstructure of mesoporous silicon prepared anodically has been exploited previously for therapeutics and biosensing, our status [...] Read more.
Silicon nanotubes (SiNTs) with unique well-defined structural morphologies have been successfully fabricated and recognized as a novel architecture in the nanoscale Si family. While the typical dendritic microstructure of mesoporous silicon prepared anodically has been exploited previously for therapeutics and biosensing, our status of utilizing SiNTs in this regard is still in its infancy. In this review, we focus on the fundamental properties of such nanotubes relevant to therapeutic applications, beginning with a description of our ability to sensitively tune the structure of a given SiNT through synthetic control and the associated detailed in vitro dissolution behavior (reflecting biodegradability). Emphasis is also placed here on the range of functional moieties available to attach to the surface of SiNTs through a summary of current studies involving surface functionalization and strategies that facilitate conjugation with molecules of interest for multiple purposes, including cell labeling, nucleotide attachment, and scaffolding of therapeutic metallic nanoparticles. Experiments addressing our ability to load the interior of a given nanotube with species capable of providing magnetic field-assisted drug delivery are also briefly described. Given the range of diverse properties demonstrated to date, we believe the future to be quite promising for employing SiNTs as therapeutic platforms. Full article
(This article belongs to the Special Issue Porous Silicon for Drug Delivery)
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Other

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Open AccessErratum
Erratum: Sun, X.; et al. Folic Acid and PEI Modified Mesoporous Silica for Targeted Delivery of Curcumin. Pharmaceutics, 2019, 11, 430
Pharmaceutics 2020, 12(7), 623; https://doi.org/10.3390/pharmaceutics12070623 - 03 Jul 2020
Viewed by 551
Abstract
The authors wish to make the following corrections to this paper [1]: [...] Full article
(This article belongs to the Special Issue Porous Silicon for Drug Delivery)
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