Structurally engineered anodic alumina nanotubes as nano-carriers for delivery of anticancer therapeutics

Enhanced anticancer effect of lysozyme-functionalized metformin-loaded shellac nanoparticles on a 3D cell model: role of the nanoparticle and payload concentrations

Here we used a 3D human hepatic tumour cell culture model to assess the in vitro efficacy of "active" metformin-loaded nanoparticles (NPs) as anticancer therapeutics. The metformin nanocarrier design was repurposed from previous studies targeting bacterial and fungal biofilms with antimicrobials loaded in protease-coated nanoparticles. These active nanocarriers were constructed with shellac cores loaded with metformin as the anticancer agent and featured a surface coating of the cationic protease lysozyme. The lysozyme's role as a nanocarrier surface coating is to partially digest the extracellular matrix (ECM) of the 3D tumour cell culture which increases its porosity and the nanocarrier penetration. Hep-G2 hepatic 3D clusteroids were formed using a water-in-water (w/w) Pickering emulsion based on an aqueous two-phase system (ATPS). Our specific metformin nano-formulation, comprising 0.25 wt% lysozyme-coated, 0.4 wt% metformin-loaded, 0.2 wt% shellac NPs sterically stabilized with 0.25 wt% Poloxamer 407, demonstrated significantly enhanced anticancer efficiency on 3D hepatic tumour cell clusteroids. We examined the role of the lysozyme surface functionality of the metformin nanocarriers in their ability to kill both 2D and 3D hepatic tumour cell cultures. The anticancer efficiency at high metformin payloads was compared with that at a high concentration of nanocarriers with a lower metformin payload. It was discovered that the high metformin payload NPs were more efficient than the lower metformin payload NPs with a higher nanocarrier concentration. This study introduces a reliable in vitro model for potential targeting of solid tumours with smart nano-therapeutics, presenting a viable alternative to animal testing for evaluating anticancer nanotechnologies.

The Role of TRAIL Signaling in Cancer: Searching for New Therapeutic Strategies

Cancer continues to pose a significant threat to global health, with its status as a leading cause of death remaining unchallenged. Within the realm of cancer research, the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) stands out as a critical player, having been identified in the 1990s as the tenth member of the TNF family. This review examines the pivotal role of TRAIL in cancer biology, focusing on its ability to induce apoptosis in malignant cells through both endogenous and exogenous pathways. We provide an in-depth analysis of TRAIL's intracellular signaling and intercellular communication, underscoring its potential as a selective anticancer agent. Additionally, the review explores TRAIL's capacity to reshape the tumor microenvironment, thereby influencing cancer progression and response to therapy. With an eye towards future developments, we discuss the prospects of harnessing TRAIL's capabilities for the creation of tailored, precision-based cancer treatments, aiming to enhance efficacy and improve patient survival rates.

[12]aneN3-modified camptothecin and PEGylated AIEgens co-assembly into core-shell nanoparticles with ROS/NTR dual-response for enhanced cancer therapy

A novel dual-responsive nanoparticle (NP) system was aimed to be developed for the co-delivery of camptothecin (CPT) and plasmid encoding TNF-related apoptosis-inducing ligand (pTRAIL) DNA in cancer therapy. The combination of the prodrug CPT and the nucleic acid condensing di-(triazole-[12]aneN3) unit with 4-nitrobenzyl ester through alkyl chains resulted in three nitroreductase (NTR) responsive amphiphiles, CNN1-CNN3 (with 5, 8, and 11 carbon chains, respectively). Among them, CNN2 was the most effective in inhibiting the proliferation of HeLa cells in the presence of fusogenic lipid DOPE. The NPs composed of CNN2, pDNA, and DOPE were further co-assembled with ROS-responsive thioketal-linked amphiphilic polymer (TTP) to afford the core-shell NPs (CNN2-DT/pDNA) with an average size of 118 nm, which exhibited high drug-loading capacity, excellent serum tolerance, and good biocompatibility. In the presence of ROS, NTR, and NADH, the core-shell NPs were decomposed, leading to the efficient release of 80% CPT and abundant pDNA. The self-assembly and delivery process of CNN2-DT NPs and DNA were clearly observed through the AIE fluorescent imaging. In vitro and in vivo results demonstrated that the CNN2-DT/pTRAIL NPs synergistically promoted 68% apoptosis of tumor cells and inhibited tumor growth with negligible toxic side effects. This study showed that the combination of prodrug and nucleic acid through dual-responsive core-shell NPs provide a spatially and temporally-controlled strategy for cancer therapy.

Structural Engineering of the Barrier Oxide Layer of Nanoporous Anodic Alumina for Iontronic Sensing

The hemispherical barrier oxide layer (BOL) closing the bottom tips of hexagonally distributed arrays of cylindrical nanochannels in nanoporous anodic alumina (NAA) membranes is structurally engineered by anodizing aluminum substrates in three distinct acid electrolytes at their corresponding self-ordering anodizing potentials. These nanochannels display a characteristic ionic current rectification (ICR) signal between high and low ionic conduction states, which is determined by the thickness and chemical composition of the BOL and the pH of the ionic electrolyte solution. The rectification efficiency of the ionic current associated with the flow of ions across the anodic BOL increases with its thickness, under optimal pH conditions. The inner surface of the nanopores in NAA membranes was chemically modified with thiol-terminated functional molecules. The resultant NAA-based iontronic system provides a model platform to selectively detect gold metal ions (Au³⁺) by harnessing dynamic ICR signal shifts as the core sensing principle. The sensitivity of the system is proportional to the thickness of the barrier oxide layer, where NAA membranes produced in phosphoric acid at 195 V with a BOL thickness of 232 ± 6 nm achieve the highest sensitivity and low limit of detection in the sub-picomolar range. This study provides exciting opportunities to engineer NAA structures with tailorable ICR signals for specific applications across iontronic sensing and other nanofluidic disciplines.

Pegylated Eu-enabled submicron alumina spheres as potential theranostics agent RD cell line as model

Objectives

This study is aimed to synthesis and evaluate PEGylated Eu enabled spherical alumina submicron particles (s-Al₂O₃:Eu) for potential theranostic applications.

Methods

This study is bisected into two parts, a) synthesis of PEGylated Eu enabled spherical alumina submicron particles (s-Al₂O₃:Eu), and b) characterization of the synthesized particles to determine their efficacy for potential theranostic applications.

The synthesis of the particles involved the following steps. In the first step, s-Al₂O₃:Eu is synthesized using solvothermal synthesis. In the next step, the particles undergo post synthesis water–ethanol treatment and calcination. The surface of the synthesized s-Al₂O₃:Eu particles is then coated by PEG to increase its biocompatibility.

Once the particles are prepared, they are characterized using different techniques. The microstructure, composition and structure of the particles is characterized using SEM, EDX and XRD techniques. The detection of the functional groups is done using FTIR analysis. The photoluminescence emission spectrum of s-Al₂O₃:Eu is studied using Photoluminescence spectroscopy. And, finally, the biocompatibility is studied using MTT assay on RD cell lines.

Results

The microstructure analysis, from the micrographs obtained from SEM, shows that the spherical alumina particles have a submicron size with narrow size distribution. The compositional analysis, as per EDX, confirms the presence of Oxygen, Aluminum and Europium in the particles. While, XRD analysis of s-Al₂O₃:Eu confirms the formation of alpha alumina phase after calcination at 700 °C. Emission peaks, obtained by Photoluminescence emission spectroscopy, show that the optimum emission intensities correspond to the transition from ⁵D₀ to ⁷F_j orbital of Eu⁺³. FTIR analysis confirms the successful coating of PEG. Finally, a cell viability of more than 86% is observed when the biocompatibility of the particles is studied, using MTT assay on RD cell lines.

Conclusions

s-Al₂O₃:Eu with narrow distribution are successfully synthesized. Structural and functional characterizations support the suitability of s-Al₂O₃:Eu as potential theranostic agent.

Synthesis and characterization of chitosan/polyvinylpyrrolidone coated nanoporous γ-Alumina as a pH-sensitive carrier for controlled release of quercetin

pH-sensitive drug delivery systems based on amphiphilic copolymers constitute a promising strategy to overcome some challenges to cancer treatment. In the present study, quercetin-loaded chitosan/polyvinylpyrrolidone/γ-Alumina nanocomposite was fabricated through a double oil in water emulsification method for the first time. γ-Alumina was incorporated to improve the drug loading efficiency and release behavior of polyvinylpyrrolidone and chitosan copolymeric hydrogel. γ-Alumina nanoparticles were obtained by the sol-gel method with a nanoporous structure, high surface area, and hydroxyl-rich surface. Quercetin, a natural anticancer agent, was loaded into the nanocomposite as a drug model. XRD and FTIR analyses confirmed the crystalline properties and chemical bonding of the prepared nanocomposite. The size of drug-loaded nanocomposites was 141 nm with monodisperse particle distribution, having a spherical shape approved by DLS analysis and FE-SEM, respectively. Incorporating γ-Alumina nanoparticles improved the encapsulation efficiency up to 95%. Besides, swelling study and the quercetin release profile demonstrated that γ-Alumina ameliorated pH sensitivity of nanocomposite and a targeted controlled release was obtained. Various release kinetic models were applied to the experimental release data to study the mechanism of drug release. Through MTT assay and flow cytometry, the quercetin-loaded nanocomposite showed significant cytotoxicity on MCF-7 breast cancer cells. Also, the enhanced apoptotic cell death confirmed the anticancer activity of γ-Alumina. These results suggest that the chitosan/polyvinylpyrrolidone/γ-Alumina nanocomposite is a novel pH-sensitive drug delivery system for anticancer applications.

Recent Advances in Nanoporous Anodic Alumina: Principles, Engineering, and Applications

The development of aluminum anodization technology features many stages. With the story stretching for almost a century, rather straightforward-from current perspective-technology, raised into an iconic nanofabrication technique. The intrinsic properties of alumina porous structures constitute the vast utility in distinct fields. Nanoporous anodic alumina can be a starting point for: Templates, photonic structures, membranes, drug delivery platforms or nanoparticles, and more. Current state of the art would not be possible without decades of consecutive findings, during which, step by step, the technique was more understood. This review aims at providing an update regarding recent discoveries-improvements in the fabrication technology, a deeper understanding of the process, and a practical application of the material-providing a narrative supported with a proper background.

In Vitro and In Vivo Models for Evaluating the Oral Toxicity of Nanomedicines

Toxicity studies for conventional oral drug formulations are standardized and well documented, as required by the guidelines of administrative agencies such as the US Food & Drug Administration (FDA), the European Medicines Agency (EMA) or European Medicines Evaluation Agency (EMEA), and the Japanese Pharmaceuticals and Medical Devices Agency (PMDA). Researchers tend to extrapolate these standardized protocols to evaluate nanoformulations (NFs) because standard nanotoxicity protocols are still lacking in nonclinical studies for testing orally delivered NFs. However, such strategies have generated many inconsistent results because they do not account for the specific physicochemical properties of nanomedicines. Due to their tiny size, accumulated surface charge and tension, sizeable surface-area-to-volume ratio, and high chemical/structural complexity, orally delivered NFs may generate severe topical toxicities to the gastrointestinal tract and metabolic organs, including the liver and kidney. Such toxicities involve immune responses that reflect different mechanisms than those triggered by conventional formulations. Herein, we briefly analyze the potential oral toxicity mechanisms of NFs and describe recently reported in vitro and in vivo models that attempt to address the specific oral toxicity of nanomedicines. We also discuss approaches that may be used to develop nontoxic NFs for oral drug delivery.

Magnetic nanoparticle decorated anodic alumina nanotubes for fluorescent detection of cathepsin B

In this work, we present the process to provide anodic alumina nanotubes with magnetic responsivity based on magnetic nanoparticles. We demonstrate the possibility to cause the motion of these composite nanotubes under magnetic field, providing them with guided mobility. The obtained magnetic anodic alumina nanotubes are completely characterized and their potential to undergo selective and effective functionalization, and stimuli-responsive load release is demonstrated. For this purpose, protease-triggered release of fluorescent molecules loaded inside the magnetic anodic alumina nanotubes (MAANTs) by selective functionalization is performed. The inner walls of the MAANTs were selectively covered with protein padding of albumin-fluorescein isothiocyanate conjugate (FITC-BSA) through means of silanization. Protein functionalization was designed to undergo proteolytic hydrolysis in presence of cathepsin B- protease highly expressed during growth and initial stages of tumor metastasis - in order to cleave peptide bond of albumin and release fluorescent fragments of the protein. Proteolytic reaction with the enzyme is performed under acidic conditions. Presented arrangement is an exemplary combination of functionalities - which are vast - and of value for applications like drug delivery and biosensing applications.

Advances in Optical Biosensors and Sensors Using Nanoporous Anodic Alumina

This review paper focuses on recent progress in optical biosensors using self-ordered nanoporous anodic alumina. We present the fabrication of self-ordered nanoporous anodic alumina, surface functionalization, and optical sensor applications. We show that self-ordered nanoporous anodic alumina has good potential for use in the fabrication of antibody-based (immunosensor), aptamer-based (aptasensor), gene-based (genosensor), peptide-based, and enzyme-based optical biosensors. The fabricated optical biosensors presented high sensitivity and selectivity. In addition, we also showed that the performance of the biosensors and the self-ordered nanoporous anodic alumina can be used for assessing biomolecules, heavy ions, and gas molecules.

Intracellular Trafficking Network and Autophagy of PHBHHx Nanoparticles and their Implications for Drug Delivery

3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBHHx), which is naturally generated by biodegradable polyhydroxyalkanoates synthesized by bacteria, is an attractive material for drug delivery due to its controllable physical properties, non-toxicity, environmental friendliness, degradable properties and good biocompatibility. However, the intracellular trafficking network pathways, especially the autophagy mechanism of PHBHHx nanoparticles (NPs), have rarely been investigated. In this paper, we successfully prepared the NPs used solvent displacement method and investigated the autophagy pathways and other intracellular trafficking mechanisms based on NPs with the assistance of Rab proteins. We found that NPs were internalized in cells mainly via clathrin endocytosis and caveolin endocytosis. Beside the classical pathways, we discovered two new pathways: the micropinocytosis early endosome (EEs)-micropinocytosis-lysosome pathway and the EEs-liposome-lysosome pathway. NPs were delivered to cells through endocytosis recycling vesicles and GLUT4 exocytosis vesicles. Similar to other nanoparticles, NPs also induced intracellular autophagy and were then degraded via endolysosomal pathways. 3-MA and CQ were used as autophagy inhibitors to avoid the degradation of NPs through lysosomes by blocking endolysosomal pathways. Tumor volumes and weights were significantly decreased when autophagy inhibitors and chemical drugs packaged in NPs were cooperatively used.

Targeted Delivery of Paclitaxel in Liver Cancer Using Hyaluronic Acid Functionalized Mesoporous Hollow Alumina Nanoparticles

Hyaluronic acid functionalized mesoporous hollow alumina nanoparticles (HMHA) were used as a tumor-targeted delivery carrier for liver cancer therapy. Paclitaxel (PAC) incorporated in the carrier by the adsorption method was analyzed by X-ray diffraction and differential scanning calorimetry. PAC was found to be in an amorphous state. The hyaluronic acid coated on the surface of mesoporous hollow alumina nanoparticles (MHA) regulated the drug release rate and the loaded samples obtained a sustained drug release. In vitro experiments demonstrated that paclitaxel-hyaluronic acid functionalized mesoporous hollow alumina nanoparticles (PAC-HMHA) had a high cellular uptake, which increased the drug level in tumor tissues and was beneficial to promote apoptosis. An in vivo tumor inhibition rate study demonstrated that PAC-HMHA (64.633 ± 4.389%) had a better antitumor effect than that of paclitaxel-mesoporous alumina nanoparticles (PAC-MHA, 56.019 ± 6.207%) and pure PAC (25.593 ± 4.115%). Therefore it can be concluded that PAC-HMHA are a prospective tumor-targeted delivery medium and can be useful for future cancer therapy.

Application of Electron Microscopes in Nanotoxicity Assessment

In this chapter, we highlight the applications of electron microscopes (EMs) in nanotoxicity assessment. EMs can provide detailed information about the size and morphology of nanomaterials (NMs), their localization in cells and tissues, the nano-bio interactions, as well as the ultrastructural changes induced by NMs exposure. Here, we share with the readers how we prepare the tissue sample, and the different types of EMs used among the nanotoxicologists. It is possible to deploy conventional EMs along or in combination with other analytical techniques, such as electron energy loss spectroscopy (EELS), energy dispersive X-ray spectroscopy (EDS or EDX), and TEM-assisted scanning transmission X-ray microscopy (STXM), toward further elemental and chemical characterization. Appropriate images are inserted to illustrate throughout this chapter.

Nanocarriers for TRAIL delivery: driving TRAIL back on track for cancer therapy

Since its initial identification, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has been shown to be capable of selectively inducing apoptosis in cancer cells. However, translation of the encouraging preclinical studies of this cytokine into the clinic has been restricted by its extremely short half-life, the presence of resistant cancer cell populations, and its inefficient in vivo delivery. Recently, there has been exceptional progress in developing novel formulations to increase the circulatory half-life of TRAIL and new combinations to treat cancers that are resistant to TRAIL. In particular, TRAIL-based nanotherapies offer the potential to improve the stability of TRAIL and prolong its half-life in plasma, to specifically deliver TRAIL to a particular target site, and to overcome resistance to TRAIL. The aim of this review is to provide an overview of the state-of-the art drug delivery systems that are currently being tested or developed to improve the biological attributes of TRAIL-based therapies.

Multiple hyperthermia-mediated release of TRAIL/SPION nanocomplex from thermosensitive polymeric hydrogels for combination cancer therapy

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) possesses strong anti-cancer potential because of its ability to specifically kill cancer cells. However, clinical use of TRAIL is impeded by its short in vivo half-life and native TRIAL-resistant cancer cell populations. To overcome these limitations, we designed a multiple magnetic hyperthermia (MHT)-mediated TRAIL release system for combination therapy using an injectable, biodegradable and thermosensitive polymeric hydrogel. In this system, positively charged TRAIL and hydrophobic superparamagnetic iron oxide nanoparticles (SPIONs) are complexed with negatively charged poly(organophosphazene) polymers via ionic and hydrophobic interactions, respectively. Transmission electron microscopy images showed a nano-sized core-shell structure of the TRAIL/SPION polymeric nanocomplex in aqueous solution that transformed into a hydrogel at body temperature. Hyperthermia can enhance the release of TRAIL from hydrogels through temperature-sensitive hydrogel dissolution. TRAIL-resistant U-87 MG cells were killed by the combination of TRAIL and multiple hyperthermia via caspase-3 and -8 active apoptosis. The hyperthermia-enhanced cytotoxicity of TRAIL was dependent on the hyperthermia cycle number and corresponding TRAIL release. Significant in vivo tumor reduction was observed by combining 2 cycles of mild MHT and TRAIL release using a single injection of TRAIL/SPION nanocomplex hydrogels without damage to main organs. Furthermore, the therapeutic outcomes can be monitored by long-term magnetic resonance imaging.

In vivo toxicological assessment of electrochemically engineered anodic alumina nanotubes: a study of biodistribution, subcutaneous implantation and intravenous injection

Electrochemically engineered anodic alumina nanotubes (AANTs) have recently shown good in vitro biocompatibility. However, in vivo toxicological and pathological studies are required to clarify the bio-safety of this novel nanomaterial. Herein, we present a pioneering pilot toxicity study on AANTs in immune-competent murine models (Balb/c mice, 8 weeks). AANTs were administered by intravenous (IV) injection and subcutaneous (SC) implantation routes considering the future toxicological implications associated with this nanomaterial for potential biomedical applications. AANTs, 736 nm long and 90 nm in outer diameter, were chosen as a nanomaterial model. We demonstrate that IV injected AANTs do not have any effect on the mortality or body weight of these animal models within 28 days at three different doses (20, 50, 100 mg kg^-1). The biodistribution of AANTs characterized by fluorescence imaging and inductively coupled plasma revealed the accumulation of AANTs in the liver and spleen after IV injection. When AANTs were injected intravenously, the highest dose of 100 mg kg^-1 caused moderate hepatotoxicity, identified by histopathological analysis. The implantation of AANTs subcutaneously and directly under the skin leads to an inflammatory response, which is a typical foreign body reaction. Taken together, this work provides new insights into the toxicity patterns of new nanomaterials such as AANTs and establishes a rationale for the design of functional AANTs for future biomedical applications.

New Frontiers in Promoting TRAIL-Mediated Cell Death: Focus on Natural Sensitizers, miRNAs, and Nanotechnological Advancements

Cancer is a multifaceted and genomically complex disease, and rapidly emerging scientific evidence is emphasizing on intra-tumor heterogeneity within subpopulations of tumor cells and rapidly developing resistance against different molecular therapeutics. There is an overwhelmingly increasing list of agents currently being tested for efficacy against cancer. In accordance with the concept that therapeutic agents must have fewer off target effects and considerable efficacy, TRAIL has emerged as one among the most deeply investigated proteins reportedly involved in differential killing of tumor cells. Considerable killing activity of TRAIL against different cancers advocated its entry into clinical trials. However, data obtained through preclinical and cell culture studies are deepening our understanding of wide-ranging mechanisms which induce resistance against TRAIL-based therapeutics. These include downregulation of death receptors, overexpression of oncogenes, inactivation of tumor suppressor genes, imbalance of pro- and anti-apoptotic proteins, and inactivation of intrinsic and extrinsic pathways. Substantial fraction of information has been added into existing pool of knowledge related to TRAIL biology and recently accumulating evidence is adding new layers to regulation of TRAIL-induced apoptosis. Certain hints have emerged underscoring miR135a-3p- and miR-143-mediated regulation of TRAIL-induced apoptosis, and natural agents have shown remarkable efficacy in improving TRAIL-based therapeutics by increasing expression of tumor suppressor miRNAs. In this review, we summarize most recent breakthroughs related to naturopathy and strategies to nanotechnologically deliver TRAIL to the target site in xenografted mice. We also set spotlight on positive and negative regulators of TRAIL-mediated signaling. Comprehensive knowledge of genetics and proteomics of TRAIL-based signaling network obtained from cancer patients of different populations will be helpful in getting a step closer to personalized medicine.

From The Mine to Cancer Therapy: Natural and Biodegradable Theranostic Silicon Nanocarriers from Diatoms for Sustained Delivery of Chemotherapeutics

Drug delivery using synthetic nanoparticles including porous silicon has been extensively used to overcome the limitations of chemotherapy. However, their synthesis has many challenges such as lack of scalability, high cost, and the use of toxic materials with concerning environmental impact. Nanoscale materials obtained from natural resources are an attractive option to address some of these disadvantages. In this paper, a new mesoporous biodegradable silicon nanoparticle (SiNP) drug carrier obtained from natural diatom silica mineral available from the mining industry is presented. Diatom silica structures are mechanically fragmented and converted into SiNPs by simple and scalable magnesiothermic reduction process. Results show that SiNPs have many desirable properties including high surface area, high drug loading capacity, strong luminescence, biodegradability, and no cytotoxicity. The in-vitro release results from SiNPs loaded with anticancer drugs (doxorubicin) demonstrate a pH-dependent and sustained drug release with enhanced cytotoxicity against cancer cells. The cells study using doxorubicin loaded SiNPs shows a significantly enhanced cytotoxicity against cancer cells compared with free drug, suggesting their considerable potential as theranostic nanocarriers for chemotherapy. Their low-cost manufacturing using abundant natural materials and outstanding chemotherapeutic performance has made them as a promising alternative to synthetic nanoparticles for drug delivery applications.

Rational engineering of nanoporous anodic alumina optical bandpass filters

Herein, we present a rationally designed advanced nanofabrication approach aiming at producing a new type of optical bandpass filters based on nanoporous anodic alumina photonic crystals. The photonic stop band of nanoporous anodic alumina (NAA) is engineered in depth by means of a pseudo-stepwise pulse anodisation (PSPA) approach consisting of pseudo-stepwise asymmetric current density pulses. This nanofabrication method makes it possible to tune the transmission bands of NAA at specific wavelengths and bandwidths, which can be broadly modified across the UV-visible-NIR spectrum through the anodisation period (i.e. time between consecutive pulses). First, we establish the effect of the anodisation period as a means of tuning the position and width of the transmission bands of NAA across the UV-visible-NIR spectrum. To this end, a set of nanoporous anodic alumina bandpass filters (NAA-BPFs) are produced with different anodisation periods, ranging from 500 to 1200 s, and their optical properties (i.e. characteristic transmission bands and interferometric colours) are systematically assessed. Then, we demonstrate that the rational combination of stacked NAA-BPFs consisting of layers of NAA produced with different PSPA periods can be readily used to create a set of unique and highly selective optical bandpass filters with characteristic transmission bands, the position, width and number of which can be precisely engineered by this rational anodisation approach. Finally, as a proof-of-concept, we demonstrate that the superposition of stacked NAA-BPFs produced with slight modifications of the anodisation period enables the fabrication of NAA-BPFs with unprecedented broad transmission bands across the UV-visible-NIR spectrum. The results obtained from our study constitute the first comprehensive rationale towards advanced NAA-BPFs with fully controllable photonic properties. These photonic crystal structures could become a promising alternative to traditional optical bandpass filters based on glass and plastic.

Bioinert Anodic Alumina Nanotubes for Targeting of Endoplasmic Reticulum Stress and Autophagic Signaling: A Combinatorial Nanotube-Based Drug Delivery System for Enhancing Cancer Therapy

Although nanoparticle-based targeted delivery systems have gained promising achievements for cancer therapy, the development of sophisticated strategies with effective combinatorial therapies remains an enduring challenge. Herein, we report the fabrication of a novel nanomaterial, so-called anodic alumina nanotubes (AANTs) for proof-of-concept cancer therapy by targeting cell signaling networks. This strategy is to target autophagic and endoplasmic reticulum (ER) stress signaling by using thapsigargin (TG)-loaded AANTs cotreated with an autophagy inhibitor 3-methyladenine (3-MA). We first show that AANTs are nontoxic and can activate autophagy in different cell types including human fibroblast cells (HFF), human monocyte cells (THP-1), and human breast cancer cells (MDA-MB 231-TXSA). Treatment with 3-MA at a nontoxic dose reduced the level of autophagy induced by AANTs, and consequently sensitized breast cancer cells to AANTs-induced cellular stresses. To target autophagic and ER stress signaling networking, breast cancer cells were treated with 3-MA together with AANTs loaded with the prototype ER stress inducer TG. We demonstrated that 3-MA enhanced the cancer cell killing effect of AANTs loaded with TG. This effect was associated with enhanced ER stress signaling due to the combination effect of TG and 3-MA. These findings not only demonstrate the excellent biocompatibility of AANTs as novel biomaterials but also provide new opportunities for developing ER- and autophagy-targeted delivery systems for future clinical cancer therapy.

In Vitro Biocompatibility of Surface-Modified Porous Alumina Particles for HepG2 Tumor Cells: Toward Early Diagnosis and Targeted Treatment

Porous alumina photoluminescence-inherent particles are produced and proposed for the development of biomarkers detectors and localized treatment of HepG2 cells. Nanoporous alumina particles (NPAPs) are amorphous, consist of hexagonally ordered nanometric pores in an alumina matrix, have high chemical stability in physiological pH, and exhibit a high inherent photoluminescence in the visible spectrum independently of their size, selectable from nanometers to tens of micrometers. The surface of NPAPs is chemically modified using two different functionalization methods, a multistep method with (3-aminopropyl)triethoxysilane (APTES) and glutaraldehyde (GLTA) and a novel simplified-step method with silane-PEG-NHS. Fourier Transform infrared spectroscopy analysis confirmed the proper surface modification of the particles for both functionalization methods. HepG2 cells were cultured during different times with growing concentrations of particles. The analysis of cytotoxicity and cell viability of HepG2 cells confirmed the good biocompatibility of NPAPs in all culture conditions. The results prove the suitability of NPAPs for developing new label-free biomarker detectors and advantageous carriers for localized drug delivery.

Charge optimized many-body (COMB) potential for Al2O3 materials, interfaces, and nanostructures

This work presents the development and applications of a new empirical, variable charge potential for Al2O3 systems within the charge optimized many-body (COMB) potential framework. The potential can describe the fundamental physical properties of Al2O3, including cohesive energy, elastic constants, defect formation energies, surface energies and phonon properties of α-Al2O3 comparable to that obtained from experiments and first-principles calculations. The potential is further employed in classical molecular dynamics (MD) simulations to validate and predict the properties of the Al (1 1 1)-Al2O3 (0 0 0 1) interface, tensile properties of Al nanowires, Al2O3 nanowires, Al2O3-covered Al nanowires, and defective Al2O3 nanowires. The results demonstrate that the potential is well-suited to model heterogeneous material systems involving Al and Al2O3. Most importantly, the parameters can be seamlessly coupled with COMB3 parameters for other materials to enable MD simulations of a wide range of heterogeneous material systems.

Nanocarbon-Coated Porous Anodic Alumina for Bionic Devices

A highly-stable and biocompatible nanoporous electrode is demonstrated herein. The electrode is based on a porous anodic alumina which is conformally coated with an ultra-thin layer of diamond-like carbon. The nanocarbon coating plays an essential role for the chemical stability and biocompatibility of the electrodes; thus, the coated electrodes are ideally suited for biomedical applications. The corrosion resistance of the proposed electrodes was tested under extreme chemical conditions, such as in boiling acidic/alkali environments. The nanostructured morphology and the surface chemistry of the electrodes were maintained after wet/dry chemical corrosion tests. The non-cytotoxicity of the electrodes was tested by standard toxicity tests using mouse fibroblasts and cortical neurons. Furthermore, the cell-electrode interaction of cortical neurons with nanocarbon coated nanoporous anodic alumina was studied in vitro. Cortical neurons were found to attach and spread to the nanocarbon coated electrodes without using additional biomolecules, whilst no cell attachment was observed on the surface of the bare anodic alumina. Neurite growth appeared to be sensitive to nanotopographical features of the electrodes. The proposed electrodes show a great promise for practical applications such as retinal prostheses and bionic implants in general.

Facile synthesis of optical microcavities by a rationally designed anodization approach: tailoring photonic signals by nanopore structure

Structural engineering of porous anodic aluminum oxide (AAO) nanostructures by anodization has been extensively studied in the past two decades. However, the transition of this technique into the fabrication of AAO-based one-dimensional photonic crystal is still challenging. Herein, we report for the first time on the fabrication of AAO optical microcavities by a rationally designed anodization approach. In our study, two feasible methods are used to fabricate microcavities with tunable resonance peak across the visible and near-infrared spectra. Distributed Bragg reflector (DBR) nanostructures are first fabricated by pulse anodization approach, in which the anodization voltage was periodically manipulated to achieve pseudosinusoidal modulation of the effective refractive index gradient along the depth of the AAO nanostructures. Microcavities were created by creating a nanoporous layer of constant porosity between two AAO-DBR nanostructures, and by introducing a shift of the phase of the porosity gradient along the depth of AAO. The position of the resonance peak in these microcavities can be linearly tuned by means of the duration of the high voltage anodization. These optical nanostructures are sensitive to alterations of the effective media inside the nanopores. The AAO microcavity shows a central wavelength shift of 2.58 ± 0.37 nm when exposed to water vapor. Our research highlights the feasibility of anodization technique to fabricate AAO-based photonic nanostructures for advanced sensing applications.

Engineered therapeutic-releasing nanoporous anodic alumina-aluminum wires with extended release of therapeutics

In this study, we present a nanoengineered therapeutic-releasing system based on aluminum wires featuring nanoporous anodic alumina layers and chitosan coatings. Nanoporous anodic alumina layers are produced on the surface of aluminum wires by electrochemical anodization. These nanoporous layers with precisely engineered nanopore geometry are used as nanocontainers for bovine serum albumin molecules labeled with fluorescein isothiocyanate (BSA-FITC), which is selected as a model drug. The surface of these therapeutic-releasing implants is coated with a biocompatible and biodegradable polymer, chitosan, in order to achieve a sustained release of protein over extended periods of time. The performance of this therapeutic-releasing device is systematically assessed through a series of experiments under static and dynamic flow conditions. In these experiments, the effect of such parameters as the number of layers of chitosan coating and the temperature and pH of the eluting medium is established. The obtained results reveal that the proposed therapeutic-releasing system based on nanoporous aluminum wires can be engineered with sustained release performance for up to 6.5 weeks, which is a critical factor for medical treatments using sensitive therapeutics such as proteins and genes when a localized delivery is desired.

An overview of nanotoxicity and nanomedicine research: principles, progress and implications for cancer therapy

The studies of nanomaterial-based drug delivery and nanotoxicity are closely interconnected.

Localized drug delivery of selenium (Se) using nanoporous anodic aluminium oxide for bone implants

Release behavior and cancer toxicity of different forms of Se loaded into nanoporous AAO were studied.

Unique AAO films with adjustable hierarchical microstructures

Anodic aluminium oxide (AAO) films with novel nano-/submicron-/micron-porous hierarchical structures have been fabricated by using a simple anodization method.

Nanoengineered drug-releasing aluminium wire implants: comparative investigation of nanopore geometry, drug release and osteoblast cell adhesion

In this study, drug-releasing aluminium (Al) wire implants featuring nanoporous alumina (NPA) layers produced by different anodization approaches are systematically investigated as potential platforms for localized drug delivery and bone therapy.

Periodically tailored titania nanotubes for enhanced drug loading and releasing performances

Structural engineering of titania nanotubes (TNTs) with periodically shaped structures was successfully demonstrated as a strategy to improve drug loading and releasing performances of TNTs/Ti implants.