Silk Fibroin Matrix Research Articles

Preparation of SF/SF-nHA double-layer scaffolds for periodental tissue regeneration

Silk fibroin (SF) film/porous SF-nanohydroxyapatite (nHA) double-layer composite scaffolds were fabricated by a combination of electrospinning, casting and freeze-drying. The results showed that the tensile strength and elongation of the SF film layer were significantly improved through the bridging effect of SF/(ε-caprolactone) fibers in the SF matrix. The pore size in SF-nHA porous scaffold layer was approximately 213 μm, and nHA enhanced the compressive strength of the scaffold. CCK-8 assay showed that the SF/SF-nHA scaffold not only had no obvious cytotoxicity but also significantly promoted cell proliferation. The scaffold has the potential to be used for periodontal tissue regeneration.

Binary ethosomes-based transdermal patches assisted by metal microneedles significantly improve the bioavailability of carvedilol

This study aimed to develop a strategy combining binary ethsomes (BES) and microneedles (MNs) to improve the bioavailability of drugs that are poorly bioavailable by oral administration, such as carvedilol (CL). The formula of BES was optimized by Box-Benhnken Designes from four aspects: particle size, zeta potential, encapsulation efficiency and cumulative release in vitro. The optimized BES was then mixed with polyvinylpyrrolidone and sprayed onto the silk fibroin matrix by electrospray to obtain transdermal drug delivery patches (TDDP). In vitro skin penetration test showed that, TDDP has much better transdermal drug release performance compared with free drugs, and MNs-assisted TDDP (MNs-TDDP) can deliver more drugs to the receiving chamber. In vivo studies indicate that MNs-TDDP can significantly reduce the fluctuation of CL concentration in plasma and increase serum level of NO, thereby lower blood pressure for a longer time. These results suggest that the bioavailability of CL can be greatly improved via administration of MNs-TDDP, compared with the oral route. Considering its advantages of non-invasiveness, convenience and good biosafety, MNs-TDDP has a promising prospect in improving the bioavailability of drugs for treating chronic diseases such as hypertension.

Developing a novel calcium magnesium silicate/graphene oxide incorporated silk fibroin porous scaffold with enhanced osteogenesis, angiogenesis and inhibited osteoclastogenesis

Recently, biofunctional ions (Mg2+, Si4+, etc) and graphene derivatives are proved to be promising in stimulating bone formation. In this study, a novel inorganic/organic composite porous scaffold based on silk fibroin (SF), graphene oxide (GO), and calcium magnesium silicate (CMS) was developed for bone repair. The porous scaffolds obtained by lyophilization showed a little difference in pore structure while GO and CMS displayed a good interaction with SF matrix. The addition of CMS with good mineralization potential and sustainedly release ability of biofunctional ions (Ca2+, Mg2+ and Si4+) increased the strength of SF scaffolds a little and facilitated the osteogenic differentiation of bone mesenchymal stem cells (BMSCs) by upregulating bone formation-related genes (ALP, COL1, OC and Runx2). The further incorporation of GO in SF scaffolds enhanced the compressive strength and water retention, and also remarkably promoted the osteogenic differentiation of BMSCs. Besides, the angiogenesis of human umbilical vein endothelial cells was significantly promoted by CMS/GO/SF scaffold extract through the upregulation of angiogenesis genes (eNOs and bFGF). Moreover, the osteoclastic formation ability of RAW264.7 cells was suppressed by the released ions from CMS/GO/SF scaffold through the down-regulation of CAK, MMP9 and TRAP. The promoted osteogenesis, angiogenesis and inhibited osteoclastogenesis functions of CMS/GO/SF composite scaffold may enable it as a novel therapy for bone repair and regeneration.

Rhein incorporated silk fibroin hydrogels with antibacterial and anti-inflammatory efficacy to promote healing of bacteria-infected burn wounds

Advanced dressings that can simultaneously prevent bacterial colonization/infection and reduce inflammation are highly desired. A simple strategy was developed to incorporate an anti-inflammatory and antibacterial drug rhein into the structure of silk fibroin (SF) matrix to fabricate a hydrogel dressing. The SF/Rhein hydrogels showed fibrous network nanostructure, high water content (~90%), high water adsorption ability (>2 folds of its own weight), acceptable mechanical strength, biocompatibility and antibacterial properties, suitable as dressings for the treatment of bacterial infected wounds. The SF/Rhein hydrogels enhanced the healing rate of burn wounds by reducing inflammation, expediting angiogenesis, and promoting skin appendages formation, being a promising candidate as wound dressings.

Enabling Selectively Tunable Mechanical Properties of Graphene Oxide/Silk Fibroin/Cellulose Nanocrystal Bionanofilms.

Enhancing and manipulating the mechanical properties of graphene oxide (GO)-based structures are challenging because the GO assembly is easily delaminated. We develop nacre-like bionanofilms whose in-plane mechanical properties can be manipulated through water vapor annealing without influencing their mechanical properties in the thickness direction. These bionanofilms are prepared from GO, silk fibroin (SF), and cellulose nanocrystals (CNCs) via a spin-assisted layer-by-layer assembly. The postannealing mechanical properties of the films are determined with atomic force microscopy (AFM) bending and nanoindentation, and it is confirmed that the mechanical properties of the bionanofilms are altered only in the in-plane direction. While AFM bending shows Young's moduli of 26.9, 36.3, 24.3, and 41.4 GPa for 15, 15 annealed, 30, and 30 annealed GO/SF/CNC trilayers, nanoindentation shows reduced moduli of 19.5 ± 2.6 and 19.5 ± 2.5 GPa before and after annealing, respectively. The unaltered mechanical properties of the bionanofilms along the thickness direction after annealing can be attributed to the CNC frame in the SF matrix acting as a support against stress in the thickness direction, while annealing reorganizes the bionanofilm structure. The tunability of the bionanofilms' mechanical properties in only one direction through structure manipulation can lead to various applications, such as e-skin, wearable sensors, and human-machine interaction devices.

Sequential growth factor exposure of human Ad-MSCs improves chondrogenic differentiation in an osteochondral biphasic implant.

Joint cartilage damage affects 10-12% of the world's population. Medical treatments improve the short-term quality of life of affected individuals but lack a long-term effect due to injury progression into fibrocartilage. The use of mesenchymal stem cells (MSCs) is one of the most promising strategies for tissue regeneration due to their ability to be isolated, expanded and differentiated into metabolically active chondrocytes to achieve long-term restoration. For this purpose, human adipose-derived MSCs (Ad-MSCs) were isolated from lipectomy and grown in xeno-free conditions. To establish the best differentiation potential towards a stable chondrocyte phenotype, isolated Ad-MSCs were sequentially exposed to five differentiation schemes of growth factors in previously designed three-dimensional biphasic scaffolds with incorporation of a decellularized cartilage matrix as a bioactive ingredient, silk fibroin and bone matrix, to generate a system capable of being loaded with pre-differentiated Ad-MSCs, to be used as a clinical implant in cartilage lesions for tissue regeneration. Chondrogenic and osteogenic markers were analyzed by reverse transcription-quantitative PCR and cartilage matrix generation by histology techniques at different time points over 40 days. All groups had an increased expression of chondrogenic markers; however, the use of fibroblast growth factor 2 (10 ng/ml) followed by a combination of insulin-like growth factor 1 (100 ng/ml)/TGFβ1 (10 ng/ml) and a final step of exposure to TGFβ1 alone (10 ng/ml) resulted in the most optimal chondrogenic signature towards chondrocyte differentiation and the lowest levels of osteogenic expression, while maintaining stable collagen matrix deposition until day 33. This encourages their possible use in osteochondral lesions, with appropriate properties for use in clinical patients.

N‐type silk fibroin/TiO2 nanocomposite transparent films: electrical and optical properties

AbstractThis paper highlights the effect of different concentrations of titanium dioxide (TiO2) nanoparticles on the electrical and optical properties of silk fibroin (SF). TiO2 based SF nanocomposite films were prepared using the solvent casting method. Uniform dispersion and agglomeration of nanoparticles, in nanocomposite films, were observed by field emission SEM. The conductivity of pure SF and nanocomposite films was determined by a four‐point probe and the TiO2 nanoparticles were found to bring high conductivity to the nanocomposite films. Dielectric strength improved with the addition of nanoparticles to the SF matrix. Dielectric constant and capacitance of the pure SF and nanocomposite films were measured using an LCR meter, which showed a 10‐fold enhancement on the addition of nanoparticles in SF. A very unusual property, i.e. negative resistance, was observed during LCR meter analysis for the nanocomposite films for a particular range of frequency (200–550 kHz), voltage (1 V) and current (0.5–1.5 μA). TiO2 nanoparticles changed the semiconducting behavior of the SF films from p‐type to n‐type as measured by the Hall effect experiment. The optical properties of pure SF and nanocomposite films were measured using a UV–visible spectrophotometer. The increased concentration of nanoparticles in the SF has effectively enhanced the absorbing coefficient, refractive index and percentage transmittance and reduced the bandgap energy. These SF/TiO2 nanocomposite films have shown the potential to be used as dielectric and high refractive index material for optoelectronics applications. © 2021 Society of Industrial Chemistry.

Facile fabrication of silk fibroin/graphene oxide composite films and real‐time morphological observation in stretching

AbstractLayer‐structured regenerated silk fibroin (SF)/graphene oxide (GO) composite films were fabricated by a facile solution casting method. Fourier transform infrared spectroscopy, X‐ray diffraction, and thermal gravity analysis confirmed the successful incorporation and uniform dispersion of graphene oxides in the SF matrix. To visualize GO's effect on the morphological evolution, atomic force microscopic images were recorded in real‐time during the composite elongation to establish a correlation between microscopic structural characters and macroscopic mechanical properties. The result showed that the incorporation of graphene oxide into the SF matrix resulted in chain conformational transition, film surface flattening, and mechanical reinforcement. Surface roughness dramatically decreased from 65 to 10 nm, while tensile modulus increased substantially from 8.61 to 22.37 MPa by adding well‐dispersed graphene oxide up to 1 wt% into the SF matrix. Through the real‐time AFM observation under the horizontal stretching mode, the surface topography of original SF films varied from tori‐spherical aggregations to rod‐like ones resulting from GO's incorporation. In the meantime, SF's hydrophobicity was also increased, as manifested by contact angle increase from 30.81° to 45.09°.

Broadband dielectric response of silk Fibroin/BaTiO3 composites: Influence of nanoparticle size and concentration

In order to advance towards more sustainable electronics generation, natural polymers with tailored dielectric response are essential. In this search, the combination of bio-based materials with active fillers in composite form, suppose one of the most viable alternatives. To achieve it, this work has explored the ability to control dielectric response of Silk Fibroin, a protein polymer by its combination with ceramic barium titanate (BaTiO3) nanoparticles. Both the effect of filler concentration (0, 5, 10, 20 and 40 wt%) and size (100 and 200 nm) has been studied in composites processed by easily scalable techniques. Samples with a homogeneous distribution of nanoparticles have been obtained. Dielectric relaxation processes assessed by broadband dielectric relaxation spectroscopy (BDS) in wide frequency (0.1 Hz–1 MHz) and temperature ranges (- 40 to 220 °C), revealed a dielectric constant increasing with filler content and decreasing with filler size, ranging from 4.4 for SF up to 142 for the SF/BaTiO3 composite with 40 wt %, at room temperature and 1 kHz. Two relaxations processes are observed, the β-relaxation and the conductivity relaxation, both with temperature-dependent behaviour. The activation energy of the conductivity process decreases with increasing nanoparticle content and decreasing size. A Maxwell-Wagner-Sillar process related to the interface between the silk fibroin matrix and the BaTiO3 nanoparticles was also identified.

Enzymatic degradability and release properties of graphene oxide/silk fibroin nanocomposite films

AbstractThe structure evolution of silk fibroin (SF) in the nanocomposite films with graphene oxide (GO) was investigated and related to the enzymatic degradability and release property. The interaction with GO was found to induce conformation transition of SF from random coil to β‐sheet. However, the surface binding constrained the rearrangement of the silk chains, leading to a decrease of β‐sheet when GO content was more than 1.0%. The crystal structure of SF played a key role in the degradation of GO/SF composites. The preferential degradation of the hydrophilic blocks resulted in a faster degradation of SF films with higher β‐sheet content. The addition of GO to SF matrix led to a slower release and a reduction of the burst release of RhB, the model compound. The release profile was well fitted to the Rigter–Peppas equation, from which the characteristic constant decreased and the diffusional exponent increased with increasing GO content but quickly leveled off when GO content was more than 1.0%. Degradation of the composites had little influence on the characteristic constant of RhB release, however, led to an increased diffusional exponent, which was more evident for the composites with higher β‐sheet content.

A facile strategy to construct flexible and conductive silk fibroin aerogel for pressure sensors using bifunctional PEG

Silk fibroin (SF) has excellent biocompatibility and can be regenerated to obtain diverse materials. However, high brittleness and poor elasticity limit its applications in flexible devices, mainly due to high amounts of β-sheet structures in SF. Herein, a flexible SF aerogel is prepared by coupling polyethylene glycol (PEG) containing double-carboxyl end group with fibroin chains. This is followed by ammonium persulfate (APS)-initiated deposition of polypyrrole (PPy) units onto the scaffold. The bifunctional PEG not only improves the elasticity of SF aerogel, but it also promotes the accumulation of pyrrole cations on the fibroin surface and guides the formation of PPy. Meanwhile, PPy distributed in the SF matrix forms an electrically conductive pathway with an encouraging static conductivity, which is responsive to environmental humidity and external pressure. The sensitivity of the prepared SF-based conductive aerogel as a pressure sensor is much better than those reported in literature. Meanwhile, the stress and resistance show good synchronization during cyclic compressions. The present work provides a promising alternative for the fabrication of fibroin-based flexible and conductive aerogels as highly sensitive pressure sensors.

Silk Fiber-Reinforced Hyaluronic Acid-Based Hydrogel for Cartilage Tissue Engineering.

A continuing challenge in cartilage tissue engineering for cartilage regeneration is the creation of a suitable synthetic microenvironment for chondrocytes and tissue regeneration. The aim of this study was to develop a highly tunable hybrid scaffold based on a silk fibroin matrix (SM) and a hyaluronic acid (HA) hydrogel. Human articular chondrocytes were embedded in a porous 3-dimensional SM, before infiltration with tyramine modified HA hydrogel. Scaffolds were cultured in chondropermissive medium with and without TGF-β1. Cell viability and cell distribution were assessed using CellTiter-Blue assay and Live/Dead staining. Chondrogenic marker expression was detected using qPCR. Biosynthesis of matrix compounds was analyzed by dimethylmethylene blue assay and immuno-histology. Differences in biomaterial stiffness and stress relaxation were characterized using a one-step unconfined compression test. Cell morphology was investigated by scanning electron microscopy. Hybrid scaffold revealed superior chondro-inductive and biomechanical properties compared to sole SM. The presence of HA and TGF-β1 increased chondrogenic marker gene expression and matrix deposition. Hybrid scaffolds offer cytocompatible and highly tunable properties as cell-carrier systems, as well as favorable biomechanical properties.

전기방사 키틴 나노섬유로 강화된 실크피브로인 기반 투명 복합 필름

본 연구에서는 전기방사 공정을 이용해 제작한 키틴 멤브레인에 실크 피브로인 수용액을 함침하여 투명한 키틴-실크피브로인 복합체 필름을 제작하였다. 키틴과 실크 피브로인의 복합화에 따라 화학 및 결정구조, 광학적 특성, 기계적 특성이 어떻게 달라지는지 알아보았다. 키틴-실크 피브로인 복합체 필름에서는 키틴 멤브레인과 실크 피브로인 필름의 특징적인 peak들이 복합화되어 나타나는 것을 확인하였다. 키틴 멤브레인은 0%(파장: 550 nm)의 투과도를 나타내지만, 키틴과 유사한 굴절률을 갖는 실크 피브로인을 키틴 멤브레인 내부에 고르게 함침함으로써 89%(파장: 550 nm)의 투과도를 갖는 투명한 복합체 필름을 형성할 수 있었다. 또한 키틴-실크 피브로인 복합체는 키틴과 실크 피브로인 사이의 상호작용과 실크 피브로인의 β-sheet 형성에 의해 단일 실크 피브로인 필름보다 높은 강도와 연신율을 가지는 것을 확인하였다.

Generation of Nano-pores in Silk Fibroin Films Using Silk Nanoparticles for Full-Thickness Wound Healing.

Silk fibroin films are used in tissue engineering due to their biocompatibility, optical clarity, and slow biodegradability. However, the relatively smooth surface and low permeability of these systems may limit some applications; thus, here, a method was developed to generate nano-pores in methanol or ethanol-treated silk fibroin films. The first step was to induce the formation of nanoparticles (50-300 nm diam.) in silk fibroin solutions by autoclaving. After drying in air, the films formed were treated to induce silk β-sheet structures, which condense the bulk silk phase and nanoparticles and phase separation and enlarge the space of bulk silk phase and nanoparticles. These films were then extracted with water to allow the condensed nanoparticles to escape, leaving homogeneous nano-pores (50-300 nm) in the silk fibroin matrix. The introduction of nano-pores resulted in enhanced permeability and minimized loss of the mechanical properties of the nano-porous silk fibroin films (NSFs) when compared to the un-autoclaving-treated silk fibroin films. NSFs promoted cell (human fibroblasts) proliferation and oxygen/nutrition perfusion and significantly enhanced the complete skin-thickness wound healing in a rat model, suggesting the potential use in tissue regeneration or as wound dressing biomaterials for clinical applications.

Encapsulation of fragrances in micron-size silk fibroin carriers via coaxial electrohydrodynamic techniques

Herein, we present the successful application of coaxial electrostatic atomization technology for encapsulation of volatile fragrances in silk fibroin (SF) matrices with l-menthol (MenOH) as a model compound. The fragrance-loaded core-shell fibers and capsules of a mean diameter of 1–2 μm were fabricated on the same apparatus, and their structural characteristics could be tuned by changing the ratio of a component in core and shell and matching with process parameters. By decreasing the concentration of the core solution, the loading capacity (LC) of electrospun fibers was up to 12 wt% with an encapsulation efficiency (EE) of ~46%. The fragrance content of capsules was 4% since a limited amount of MenOH incorporated in the case of electrospray. Impregnation with alcohol was effective in hardening SF shell and thus significantly decreasing the diffusion of aroma molecules. The fragrance release profile and rate of the composites were controlled by the degree of crystallinity of SF matrix and the shell thickness. Also, the fragrance microcapsules could be directly deposited on the fabric surface during electrospray and showed good washing durability.

Porous Silk Fibroin/Cellulose Hydrogels for Bone Tissue Engineering via a Novel Combined Process Based on Sequential Regeneration and Porogen Leaching.

Scaffolds used for bone tissue engineering need to have a variety of features to accommodate bone cells. The scaffold should mimic natural bone, it should have appropriate mechanical strength, support cell differentiation to the osteogenic lineage, and offer adequate porosity to allow vascularization and bone in-growth. In this work, we aim at developing a new process to fabricate such materials by creating a porous composite material made of silk fibroin and cellulose as a suitable scaffold of bone tissue engineering. Silk fibroin and cellulose are both dissolved together in N,N-dimethylacetamide/LiCl and molded to a porous structure using NaCl powder. The hydrogels are prepared by a sequential regeneration process: cellulose is solidified by water vapor treatment, while the remaining silk fibroin in the hydrogel is insolubilized by methanol, which leads to a cellulose framework structure embedded in a silk fibroin matrix. Finally, the hydrogels are soaked in water to dissolve the NaCl for making a porous structure. The cellulose composition results in improving the mechanical properties for the hydrogels in comparison to the silk fibroin control material. The pore size and porosity are estimated at around 350 µm and 70%, respectively. The hydrogels support the differentiation of MC3T3 cells to osteoblasts and are expected to be a good scaffold for bone tissue engineering.

Tailoring of electrical and optical properties of regenerated silk fibroin films with metal oxides

In this study, silk fibroin was used as a matrix to incorporate the metal oxide nanoparticles i.e. zinc oxide (ZnO) and copper oxide (CuO) to form transparent nanocomposite films by solvent casting method. The effect of metal oxide nanoparticles and their concentrations on the conductivity of silk fibroin film were detected by a four-point probe instrument. As the thickness of the films was reduced, the conductivity increased. Hall Effect experiment was carried out to determine the carrier (electron or holes) concentration and identification of the semiconducting behaviour of nanocomposite films. Pure silk fibroin (SF) film showed p-type semiconducting behaviour. Incorporation of zinc oxide and copper oxide nanoparticles in the silk fibroin matrix makes it n-type and p-type semiconductor, respectively. Uniform dispersion of metal oxide nanoparticles in the silk fibroin matrix was observed through field emission scanning electron microscopy. The UV–Vis spectra of nanocomposite films showed 82–84% transmittance and reduction in refractive index. Addition of metal oxide nanoparticles reduced the β sheet content and percentage crystallinity of silk fibroin as observed by FTIR and XRD, respectively. The structural alterations at the molecular level reveal their relationship with electrical and optical properties.

Luminescent sensor based on the lanthanide-fibroin composite

Abstract This work aims to produce luminescent sensors based on lanthanide ions and silk fibroin composite films. Associating the physicochemical properties of fibroin with the spectroscopic properties of lanthanide ions can be a strategy to develop a new generation of biocompatible and biodegradable sensors with high transparency in the visible region. The results presented herein are a natural consequence of a previous study that used europium ions as structural probes in the composite fibroin matrix and investigated their potential application as photonic devices. Here, highly transparent thin films containing the silk fibroin matrix and an Eu3+ complex were produced by dip-coating under controlled conditions. Europium thenoyltrifluoroacetonate was employed as the luminescent component of the proposed sensor. The films were characterized by electronic spectroscopy in the UV–Vis region and photoluminescence. The effect of complex insertion on the refraction index of the silk fibroin film was studied. The results showed a high-intensity emission that is characteristic of europium β-diketone chelates, and the intensity of the 5D0 → 7F2 transition depended on the ammonia vapor concentration. To understand the whole process, different composite films were prepared, and the results corroborated the potential use of this system as a photonic sensor of vapors.

An all-silk-derived functional nanosphere matrix for sequential biomolecule delivery and in situ osteochondral regeneration

Endogenous repair of osteochondral defect is usually limited by the insufficient number of cells in the early stage and incomplete cell differentiation in the later stage. The development of drug delivery systems for sequential release of pro-migratory and pro-chondrogenic molecules to induce endogenous bone marrow-derived mesenchymal stem cells (BMSCs) recruitment and chondrogenic differentiation is highly desirable for in situ osteochondral regeneration. In this study, a novel, all-silk-derived sequential delivery system was fabricated by incorporating the tunable drug-loaded silk fibroin (SF) nanospheres into a SF porous matrix. The loading efficiency and release kinetics of biomolecules depended on the initial SF/polyvinyl alcohol (PVA) concentrations (0.2%, 1% and 5%) of the nanospheres, as well as the hydrophobicity of the loaded molecules, resulting in controllable and programmed delivery profiles. Our findings indicated that the 5% nanosphere-incorporated matrix showed a rapid release of E7 peptide during the first 120 h, whereas the 0.2% nanosphere-incorporated matrix provided a slow and sustained release of Kartogenin (KGN) longer than 30 days. During in vitro culture of BMSCs, this functional SF matrix incorporated with E7/KGN nanospheres showed good biocompatibility, as well as enhanced BMSCs migration and chondrogenic differentiation through the release of E7 and KGN. Furthermore, when implanted into rabbit osteochondral defect, the SF nanosphere matrix with sequential E7/KGN release promoted the regeneration of both cartilage and subchondral bone. This work not only provided a novel all-silk-derived drug delivery system for sequential release of molecules, but also a functional tissue-engineered scaffold for osteochondral regeneration.

Electroactive Silk Fibroin Films for Electrochemically Enhanced Delivery of Drugs

AbstractBiomaterials capable of controlling the delivery of drugs have the potential to treat a variety of conditions. Herein, the preparation of electrically conductive silk fibroin film‐based drug delivery devices is described. Casting aqueous solutions of Bombyx mori silk fibroin, followed by drying and annealing to impart β‐sheets to the silk fibroin, assure that the materials are stable for further processing in water; and the silk fibroin films are rendered conductive by generating an interpenetrating network of a copolymer of pyrrole and 3‐amino‐4‐hydroxybenzenesulfonic acid in the silk fibroin matrix (characterized by a variety of techniques including circular dichroism, Fourier‐transform infrared spectroscopy, nuclear magnetic resonance, Raman spectroscopy, resistance measurements, scanning electron microscopy‐energy dispersive X‐ray spectroscopy, thermogravimetric analysis, X‐ray diffraction, and X‐ray photoelectron spectroscopy). Fibroblasts adhere on the surface of the biomaterials (viability assessed using an (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay and visualized using a confocal microscope), and a fluorescently labeled drug (Texas‐Red Gentamicin) can be loaded electrochemically and released (µg cm−2 quantities) in response to the application of an electrical stimulus.