Augmented physical, mechanical, and cellular responsiveness of gelatin-aldehyde modified xanthan hydrogel through incorporation of silicon nanoparticles for bone tissue engineering

Bioactive scaffolds fabricated from a combination of organic and inorganic biomaterials are a promising approach for addressing defects in bone tissue engineering. In the present study, a self-crosslinked nanocomposite hydrogel, composed of gelatin/aldehyde-modified xanthan (Gel-AXG) is successfully developed by varying concentrations of porous silicon nanoparticles (PSiNPs). The effect of PSiNPs incorporation on physical, mechanical, and biological performance of the nanocomposite hydrogel is evaluated. Morphological analysis reveals formation of highly porous 3D microstructures with interconnected pores in all nanocomposite hydrogels. Increased content of PSiNPs results in a lower swelling ratio, reduced porosity and pore size, which in turn impeded media penetration and slowed down the degradation process. In addition, remarkable enhancements in dynamic mechanical properties are observed in Gel-AXG-8%Si (compressive strength: 0.6223 MPa at 90 % strain and compressive modulus: 0.054 MPa), along with improved biomineralization ability via hydroxyapatite formation after immersion in simulated body fluid (SBF). This optimized nanocomposite hydrogel provides a sustained release of Si ions at safe dose levels. Furthermore, in-vitro cytocompatibility studies using MG-63 cells exhibited remarkable performance in terms of cell attachment, proliferation, and ALP activity for Gel-AXG-8%Si. These findings suggest that the prepared nanocomposite hydrogel holds promising potential as a scaffold for bone tissue engineering.

Dissolving microneedle-assisted long-acting Liraglutide delivery to control type 2 diabetes and obesity

Integrating nanoparticles (NPs) as a smart and targeted tool for drug delivery with dissolving microneedle (DMN) patch, the non-invasive device for drug delivery, is a promising for future therapeutic delivery applications. Liraglutide (Lira) encapsulation in poly (lactic-co-glycolic acid) (PLGA) NPs provides a sustained release of Lira to 15 days in a biphasic profile which 80% of released content happens in the first 8 days. Embedding such sustained release NPs in the DMN comprising poly vinyl pyrrolidone (PVP) 50% w/v, eliminates the need for Lira subcutaneous injection. Additionally, NPs containing DMN enhance mechanical strength of needles to 5.31 N compared to DMN with pure Lira content which was 4.32 N. The flexible backing layer of the DMN was obtained via blending of PVP and poly vinyl alcohol (PVA) in 10% w/v. Circular dichroism (CD) analysis showed that Lira encapsulated in NPs maintained its native secondary structure even after solidification in DMN. In this study, the capacity of 2 kinds of 500 μm and 1000 μm needles to deliver the desired dose of drug was obtained based on experimental and mathematical methods.

Characteristics of SARS-CoV2 that may be useful for nanoparticle pulmonary drug delivery

As a non-invasive method of local and systemic drug delivery, the administration of active pharmaceutical ingredients (APIs) via the pulmonary route represents an ideal approach for the therapeutic treatment of pulmonary diseases. The pulmonary route provides a number of advantages, including the rapid absorption which results from a high level of vascularisation over a large surface area and the successful avoidance of first-pass metabolism. Aerosolization of nanoparticles (NPs) is presently under extensive investigation and exhibits a high potential for targeted delivery of therapeutic agents for the treatment of a wide range of diseases. NPs need to possess specific characteristics to facilitate their transport along the pulmonary tract and appropriately overcome the barriers presented by the pulmonary system. The most challenging aspect of delivering NP-based drugs via the pulmonary route is developing colloidal systems with the optimal physicochemical parameters for inhalation. The physiochemical properties of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) have been investigated as a template for the synthesis of NPs to assist in the formulation of virus-like particles (VLPs) for pharmaceutical delivery, vaccine production and diagnosis assays.

Impact of resveratrol-mediated increase in uterine artery blood flow on fetal haemodynamics, blood pressure and oxygenation in sheep

NEW FINDINGS

What is the central question of this study? Uterine artery blood flow helps to maintain fetal oxygen and nutrient delivery. We investigated the effects of increased uterine artery blood flow mediated by resveratrol on fetal growth, haemodynamics, blood pressure regulation and oxygenation in pregnant sheep. What is the main finding and its importance? Fetuses from resveratrol-treated ewes were significantly larger and exhibited a haemodynamic profile that might promote peripheral growth. Absolute uterine artery blood flow was positively correlated with umbilical vein oxygen saturation, absolute fetal oxygen delivery and fetal growth. Increasing uterine artery blood flow with compounds such as resveratrol might have clinical significance for pregnancy conditions in which fetal growth and oxygenation are compromised.

ABSTRACT

High placental vascular resistance hinders uterine artery (UtA) blood flow and fetal substrate delivery. In the same group of animals as the present study, we have previously shown that resveratrol (RSV) increases UtA blood flow, fetal weight and oxygenation in an ovine model of human pregnancy. However, the mechanisms behind changes in growth and the effects of increases in UtA blood flow on fetal circulatory physiology have yet to be investigated. Twin-bearing ewes received s.c. vehicle (VEH, n = 5) or RSV (n = 6) delivery systems at 113 days of gestation (term = 150 days). Magnetic resonance imaging was performed at 123-124 days to quantify fetal volume, blood flow and oxygen saturation of major fetal vessels. At 128 days, i.v. infusions of sodium nitroprusside and phenylephrine were administered to study the vascular tone of the fetal descending aorta. Maternal RSV increased fetal body volume (P = 0.0075) and weight (P = 0.0358), with no change in brain volume or brain weight. There was a positive relationship between absolute UtA blood flow and umbilical vein oxygen saturation, absolute fetal oxygen delivery and combined fetal twin volume (all P ≤ 0.05). There were no differences between groups in fetal haemodynamics or blood pressure regulation except for higher blood flow to the lower body in RSV fetuses (P = 0.0170). The observed increase in fetal weight might be helpful in pregnancy conditions in which fetal growth and oxygen delivery are compromised. Further preclinical investigations on the mechanism(s) accounting for these changes and the potential to improve growth in complicated pregnancies are warranted.

Subcutaneous maternal resveratrol treatment increases uterine artery blood flow in the pregnant ewe and increases fetal but not cardiac growth

KEY POINTS

Substrate restriction during critical developmental windows of gestation programmes offspring for a predisposition towards cardiovascular disease in adult life. This study aimed to determine the effect of maternal resveratrol (RSV) treatment in an animal model in which chronic fetal catheterisation is possible and the timing of organ maturation reflects that of the human. Maternal RSV treatment increased uterine artery blood flow, fetal oxygenation and fetal weight. RSV was not detectable in the fetal circulation, indicating that it may not cross the sheep placenta. This study highlights RSV as a possible intervention to restore fetal substrate supply in pregnancies affected by placental insufficiency.

ABSTRACT

Suboptimal in utero environments with reduced substrate supply during critical developmental windows of gestation predispose offspring to non-communicable diseases such as cardiovascular disease (CVD). Improving fetal substrate supply in these pregnancies may ameliorate the predisposition these offspring have toward adult-onset CVD. This study aimed to determine the effect of maternal resveratrol (RSV) supplementation on uterine artery blood flow and the direct effects of RSV on the fetal heart in a chronically catheterised sheep model of human pregnancy. Maternal RSV treatment significantly increased uterine artery blood flow as measured by phase contrast magnetic resonance imaging, mean gestational fetal P a O 2 and S a O 2 as well as fetal weight. RSV was not detectable in the fetal circulation, and mRNA and protein expression of the histone/protein deacetylase SIRT1 did not differ between treatment groups. No effect of maternal RSV supplementation on AKT/mTOR or CAMKII signalling in the fetal left ventricle was observed. Maternal RSV supplementation is capable of increasing fetal oxygenation and growth in an animal model in which cardiac development parallels that of the human.

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.

Manipulating human dendritic cell phenotype and function with targeted porous silicon nanoparticles

Dendritic cells (DC) are the most potent antigen-presenting cells and are fundamental for the establishment of transplant tolerance. The Dendritic Cell-Specific Intracellular adhesion molecule-3-Grabbing Non-integrin (DC-SIGN; CD209) receptor provides a target for dendritic cell therapy. Biodegradable and high-surface area porous silicon (pSi) nanoparticles displaying anti-DC-SIGN antibodies and loaded with the immunosuppressant rapamycin (Sirolimus) serve as a fit-for-purpose platform to target and modify DC. Here, we describe the fabrication of rapamycin-loaded DC-SIGN displaying pSi nanoparticles, the uptake efficiency into DC and the extent of nanoparticle-induced modulation of phenotype and function. DC-SIGN antibody displaying pSi nanoparticles favourably targeted and were phagocytosed by monocyte-derived and myeloid DC in whole human blood in a time- and dose-dependent manner. DC preconditioning with rapamycin-loaded nanoparticles, resulted in a maturation resistant phenotype and significantly suppressed allogeneic T-cell proliferation.

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.

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.

Nanostructured Silicon-Based Fingerprint Dusting Powders for Enhanced Visualization and Detection by Mass Spectrometry

Porous silicon microparticles (pSi MPs) functionalized with fluorescent dyes (lissamine and carboxy-5-fluorescein) and intrinsically luminescent pSi MPs were explored as novel fingerprint dusting powders. The versatility of luminescent pSi MPs is demonstrated through time-gated imaging of their long-lived (lifetime>28 μs) near-IR emission, and mass spectrometry analysis of fingerprints dusted with luminescent pSi MPs to provide further information on exogenous small molecules present in latent fingerprints.

"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.

Fabrication and Characterization of a Porous Silicon Drug Delivery System with an Initiated Chemical Vapor Deposition Temperature-Responsive Coating

This paper reports on the fabrication of a pSi-based drug delivery system, functionalized with an initiated chemical vapor deposition (iCVD) polymer film, for the sustainable and temperature-dependent delivery of drugs. The devices were prepared by loading biodegradable porous silicon (pSi) with a fluorescent anticancer drug camptothecin (CPT) and coating the surface with temperature-responsive poly(N-isopropylacrylamide-co-diethylene glycol divinyl ether) (pNIPAM-co-DEGDVE) or non-stimulus-responsive poly(aminostyrene) (pAS) via iCVD. CPT released from the uncoated oxidized pSi control with a burst release fashion (∼21 nmol/(cm(2) h)), and this was almost identical at temperatures both above (37 °C) and below (25 °C) the lower critical solution temperature (LCST) of the switchable polymer used, pNIPAM-co-DEGDVE (28.5 °C). In comparison, the burst release rate from the pSi-pNIPAM-co-DEGDVE sample was substantially slower at 6.12 and 9.19 nmol/(cm(2) h) at 25 and 37 °C, respectively. The final amount of CPT released over 16 h was 10% higher at 37 °C compared to 25 °C for pSi coated with pNIPAM-co-DEGDVE (46.29% vs 35.67%), indicating that this material can be used to deliver drugs on-demand at elevated temperatures. pSi coated with pAS also displayed sustainable drug delivery profiles, but these were independent of the release temperature. These data show that sustainable and temperature-responsive delivery systems can be produced by functionalization of pSi with iCVD polymer films. Benefits of the iCVD approach include the application of the iCVD coating after drug loading without causing degradation of the drug commonly caused by exposure to factors such as solvents or high temperatures. Importantly, the iCVD process is applicable to a wide array of surfaces as the process is independent of the surface chemistry and pore size of the nanoporous matrix being coated.

Controlled Delivery of Levothyroxine Using Porous Silicon as a Drug Nanocontainer

Porous silicon (pSi) materials are regarded as promising drug delivery vehicles due to their biocompatibility, in vivo degradation, and resorption. We examine pSi films as a platform for the controlled delivery of levothyroxine, as a means to overcome problems with consistent dosage of this drug by oral administration. Oxidized pSi films were modified with 3-(aminopropyl)triethoxysilane (APTES), creating a surface chemistry that increased levothyroxine drug loading capacity by 50 % and sustained drug release under physiological conditions for 14 days. Release kinetics from APTES-functionalized films initially followed a zero-order release profile, which is highly desirable for drug delivery. The loading and release profiles of levothyroxine suggest that the film size required to deliver a therapeutic dose is feasible for further consideration as an implantable delivery system.

Rapid, metal-free hydrosilanisation chemistry for porous silicon surface modification

Here, we report a novel surface modification for porous silicon (pSi). Hydroxyl-terminated pSi surfaces are modified with a hydrosilane via Si-H activation using the Lewis acid catalyst tris(pentafluorophenyl) borane. This surface reaction is fast and efficient at room temperature, and leads to a surface stabilised against hydrolytic attack in aqueous media. The resulting surface shows promise as a substrate for surface-assisted laser desorption/ionisation mass spectrometry.

Surface engineering of porous silicon to optimise therapeutic antibody loading and release

Infliximab antibodies released from porous silicon microparticles can sequester the proinflammatory cytokine, tumor necrosis factor-α (TNF-α), which is elevated in uveitis and non-healing chronic wounds.

Porous silicon nanoparticles as a nanophotocathode for photoelectrochemical water splitting

An investigation on the nanophotocathode fabrication using electrochemically anodised pSi NPs for photoelectrochemical water splitting.

Biomolecule detection in porous silicon based microcavitiesviaeuropium luminescence enhancement

The ability of a porous silicon microcavity (pSiMC) to act as a luminescence enhancing sensor was confirmed using Eu(iii) complex labelled streptavidin as a model analyte on a biotin-modified pSiMC.

Combination of iCVD and porous silicon for the development of a controlled drug delivery system

We describe a pH responsive drug delivery system which was fabricated using a novel approach to functionalize biodegradeable porous silicon (pSi) by initiated chemical vapor deposition (iCVD). The assembly involved first loading a model drug (camptothecin, CPT) into the pores of the pSi matrix followed by capping the pores with a thin pH responsive copolymer film of poly(methacrylic acid-co-ethylene dimethacrylate) (p(MAA-co-EDMA)) via iCVD. Release of CPT from uncoated pSi was identical in two buffers at pH 1.8 and pH 7.4. In contrast, the linear release rate of CPT from the pSi matrix with the p(MAA-co-EDMA) coating was dependent on the pH; release of CPT was more than four times faster at pH 7.4 (13.1 nmol/(cm(2) h)) than at pH 1.8 (3.0 nmol/(cm(2) h)). The key advantage of this drug delivery approach over existing ones based on pSi is that the iCVD coating can be applied to the pSi matrix after drug loading without degradation of the drug because the process does not expose the drug to harmful solvents or high temperatures and is independent of the surface chemistry and pore size of the nanoporous matrix.

Polymerization-Amplified Optical DNA Detection on Porous Silicon Templates

A porous silicon-based optical DNA sensor is described herein, which enables rapid DNA detection. The DNA sensor relies on the specificity of the DNA base pairing in conjunction with an interferometric optical signal amplification step based on polymer formation within the porous silicon layer to detect the DNA targets in a highly selective fashion. We demonstrate that it is possible to discriminate between DNA strands exhibiting even a single nucleotide mismatch using this sensor.

Porous silicon-based nanostructured microparticles as degradable supports for solid-phase synthesis and release of oligonucleotides

We describe the preparation of several types of porous silicon (pSi) microparticles as supports for the solid-phase synthesis of oligonucleotides. The first of these supports facilitates oligonucleotide release from the nanostructured support during the oligonucleotide deprotection step, while the second type of support is able to withstand the cleavage and deprotection of the oligonucleotides post synthesis and subsequently dissolve at physiological conditions (pH = 7.4, 37°C), slowly releasing the oligonucleotides. Our approach involves the fabrication of pSi microparticles and their functionalisation via hydrosilylation reactions to generate a dimethoxytrityl-protected alcohol on the pSi surface as an initiation point for the synthesis of short oligonucleotides.

Controlled drug delivery from composites of nanostructured porous silicon and poly(L-lactide)

AIMS

Porous silicon (pSi) and poly(L-lactide) (PLLA) both display good biocompatibility and tunable degradation behavior, suggesting that composites of both materials are suitable candidates as biomaterials for localized drug delivery into the human body. The combination of a pliable and soft polymeric material with a hard inorganic porous material of high drug loading capacity may engender improved control over degradation and drug release profiles and be beneficial for the preparation of advanced drug delivery devices and biodegradable implants or scaffolds.

MATERIALS & METHODS

In this work, three different pSi and PLLA composite formats were prepared. The first format involved grafting PLLA from pSi films via surface-initiated ring-opening polymerization (pSi-PLLA [grafted]). The second format involved spin coating a PLLA solution onto oxidized pSi films (pSi-PLLA [spin-coated]) and the third format consisted of a melt-cast PLLA monolith containing dispersed pSi microparticles (pSi-PLLA [monoliths]). The surface characterization of these composites was performed via infrared spectroscopy, scanning electron microscopy, atomic force microscopy and water contact angle measurements. The composite materials were loaded with a model cytotoxic drug, camptothecin (CPT). Drug release from the composites was monitored via fluorimetry and the release profiles of CPT showed distinct characteristics for each of the composites studied.

RESULTS

In some cases, controlled CPT release was observed for more than 5 days. The PLLA spin coat on pSi and the PLLA monolith containing pSi microparticles both released a CPT payload in accordance with the Higuchi and Ritger-Peppas release models. Composite materials were also brought into contact with human lens epithelial cells to determine the extent of cytotoxicity.

CONCLUSION

We observed that all the CPT containing materials were highly efficient at releasing bioactive CPT, based on the cytotoxicity data.

Stimulus-responsiveness and drug release from porous silicon films ATRP-grafted with poly(N-isopropylacrylamide)

In this report, we employ surface-initiated atom transfer radical polymerization (SI-ATRP) to graft a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM), of controlled thickness from porous silicon (pSi) films to produce a stimulus-responsive inorganic-organic composite material. The optical properties of this material are studied using interferometric reflectance spectroscopy (IRS) above and below the lower critical solution temperature (LCST) of the PNIPAM graft polymer with regard to variation of pore sizes and thickness of the pSi layer (using discrete samples and pSi gradients) and also the thickness of the PNIPAM coatings. Our investigations of the composite's thermal switching properties show that pore size, pSi layer thickness, and PNIPAM coating thickness critically influence the material's thermoresponsiveness. This composite material has considerable potential for a range of applications including temperature sensors and feedback controlled drug release. Indeed, we demonstrate that modulation of the temperature around the LCST significantly alters the rate of release of the fluorescent anticancer drug camptothecin from the pSi-PNIPAM composite films.