Functionalized gold nanoparticle-polypyrrole nanobiocomposite with high effective surface area for electrochemical/pH dual stimuli-responsive smart release of insulin

Targeted protein delivery based on stimuli-triggered nanomedicine

Protein-based drugs have shown unique advantages to treat various diseases in recent years. However, most protein therapeutics in clinical use are limited to extracellular targets with low delivery efficiency. To realize targeted protein delivery, a series of stimuli-triggered nanoparticle formulations have been developed to improve delivery efficiency and reduce off-target release. These smart nanoparticles are designed to release cargo proteins in response to either internal or external stimuli at pathological tissues. In this way, varieties of protein-based drugs including antibodies, enzymes, and pro-apoptotic proteins can be effectively delivered to desired sites for the treatment of cancer, inflammation, metabolic diseases, and so on with minimal side effects. In this review, recent advances in the design of stimuli-triggered nanomedicine for targeted protein delivery in different biomedical applications will be discussed. A deeper understanding of these emerging strategies helps develop more efficient protein delivery systems for clinical use in the future.

Drug delivery via a 3D electro-swellable conjugated polymer hydrogel

Spatiotemporal controlled drug delivery minimizes side-effects and enables therapies that require specific dosing patterns. Conjugated polymers (CP) can be used for electrically controlled drug delivery; however so far, most demonstrations were limited to molecules up to 500 Da. Larger molecules could be incorporated only during the CP polymerization and thus limited to a single delivery. This work harnesses the record volume changes of a glycolated polythiophene p(g3T2) for controlled drug delivery. p(g3T2) undergoes reversible volumetric changes of up to 300% during electrochemical doping, forming pores in the nm-size range, resulting in a conducting hydrogel. p(g3T2)-coated 3D carbon sponges enable controlled loading and release of molecules spanning molecular weights of 800-6000 Da, from simple dyes up to the hormone insulin. Molecules are loaded as a combination of electrostatic interactions with the charged polymer backbone and physical entrapment in the porous matrix. Smaller molecules leak out of the polymer while larger ones could not be loaded effectively. Finally, this work shows the temporally patterned release of molecules with molecular weight of 1300 Da and multiple reloading and release cycles without affecting the on/off ratio.

Electrochemical deposition of Ppy/Dex/ECM coatings and their regulation on cellular responses through electrical controlled drug release

Bone tissue engineering requires a material that can simultaneously promote osteogenic differentiation and anti-inflammatory effects at specific times in response to a series of problems after bone implantation. In this study, the porous network-like titanium matrix was constructed and polypyrrole/dexamethasone (Ppy/Dex) composite coatings with three-dimensional nano-network structure were prepared by electrochemical deposition. The biocompatibility of the composite coatings was further improved by the composite of the extracellular matrix (ECM). The Ppy/Dex/ECM composite coatings released Dex by changing the redox state of Ppy under the electrical stimulation of negative pulses, achieving a drug release controlled by electric field. In terms of osteogenic differentiation, the Ppy/Dex/ECM composite coatings exhibited the best osteogenic activity under electrical controlled release, indicating the synergistic effect of Dex and ECM on osteogenic differentiation. In terms of anti-inflammatory properties, ECM exhibited simultaneous inhibition of both pro- and anti-inflammatory process, while Dex demonstrated significant promotion of anti-inflammatory processes. In this work, the effect of electrical controlled drug release on osteogenic differentiation and inflammation in the ECM cell microenvironment was achieved by preparing Ppy/Dex/ECM composite coatings, which is of great significance for bone tissue engineering and regenerative medicine.

Biodegradable bioelectronics for biomedical applications

Biodegradable polymers have been widely used in tissue engineering with the potential to be replaced by regenerative tissue. While conventional bionic interfaces are designed to be implanted in living tissue and organs permanently, biocompatible and biodegradable electronic materials are now progressing a paradigm shift towards transient and regenerative bionic engineering. For example, biodegradable bioelectronics can monitor physiologies in a body, transiently rehabilitate disease symptoms, and seamlessly form regenerative interfaces from synthetic electronic devices to tissues by reducing inflammatory foreign-body responses. Conventional electronic materials have not readily been considered biodegradable. However, several strategies have been adopted for designing electroactive and biodegradable materials systems: (1) conductive materials blended with biodegradable components, (2) molecularly engineered conjugated polymers with biodegradable moieties, (3) naturally derived conjugated biopolymers, and (4) aqueously dissolvable metals with encapsulating layers. In this review, we endeavor to present the technical bridges from electrically active and biodegradable material systems to edible and biodegradable electronics as well as transient bioelectronics with pre-clinical bio-instrumental applications, including biodegradable sensors, neural and tissue engineering, and intelligent drug delivery systems.

Porous biomaterials for tissue engineering: a review

The field of biomaterials has grown rapidly over the past decades. Within this field, porous biomaterials have played a remarkable role in: (i) enabling the manufacture of complex three-dimensional structures; (ii) recreating mechanical properties close to those of the host tissues; (iii) facilitating interconnected structures for the transport of macromolecules and cells; and (iv) behaving as biocompatible inserts, tailored to either interact or not with the host body. This review outlines a brief history of the development of biomaterials, before discussing current materials proposed for use as porous biomaterials and exploring the state-of-the-art in their manufacture. The wide clinical applications of these materials are extensively discussed, drawing on specific examples of how the porous features of such biomaterials impact their behaviours, as well as the advantages and challenges faced, for each class of the materials.

Bifunctional conducting polymer matrices with antibacterial and neuroprotective effects

Current trends in the field of neural tissue engineering include the design of advanced biomaterials combining excellent electrochemical performance with versatile biological characteristics. The purpose of this work was to develop an antibacterial and neuroprotective coating based on a conducting polymer - poly(3,4-ethylenedioxypyrrole) (PEDOP), loaded with an antibiotic agent - tetracycline (Tc). Employing an electrochemical technique to immobilize Tc within a growing polymer matrix allowed to fabricate robust PEDOP/Tc coatings with a high charge storage capacity (63.65 ± 6.05 mC/cm2), drug release efficiency (629.4 µg/cm2 ± 62.7 µg/cm2), and low charge transfer resistance (2.4 ± 0.1 kΩ), able to deliver a stable electrical signal. PEDOP/Tc were found to exhibit strong antimicrobial effects against Gram-negative bacteria Escherichia coli, expressed through negligible adhesion, reduction in viability, and a characteristic elongation of bacterial cells. Cytocompatibility and neuroprotective effects were evaluated using a rat neuroblastoma B35 cell line, and were analyzed using MTT, cell cycle, and Annexin-V apoptosis assays. The presence of Tc was found to enhance neural cell viability and neurite outgrowth. The results confirmed that PEDOP/Tc can serve as an efficient neural electrode coating able to enhance charge transfer, as well as to exhibit bifunctional biological characteristics, different for eukaryotic and prokaryotic cells.

Stimulus-Responsive Nanomedicines for Disease Diagnosis and Treatment

Stimulus-responsive drug delivery systems generally aim to release the active pharmaceutical ingredient (API) in response to specific conditions and have recently been explored for disease treatments. These approaches can also be extended to molecular imaging to report on disease diagnosis and management. The stimuli used for activation are based on differences between the environment of the diseased or targeted sites, and normal tissues. Endogenous stimuli include pH, redox reactions, enzymatic activity, temperature and others. Exogenous site-specific stimuli include the use of magnetic fields, light, ultrasound and others. These endogenous or exogenous stimuli lead to structural changes or cleavage of the cargo carrier, leading to release of the API. A wide variety of stimulus-responsive systems have been developed-responsive to both a single stimulus or multiple stimuli-and represent a theranostic tool for disease treatment. In this review, stimuli commonly used in the development of theranostic nanoplatforms are enumerated. An emphasis on chemical structure and property relationships is provided, aiming to focus on insights for the design of stimulus-responsive delivery systems. Several examples of theranostic applications of these stimulus-responsive nanomedicines are discussed.

In vitro attenuation of astrocyte activation and neuroinflammation through ibuprofen-doping of poly(3,4-ethylenedioxypyrrole) formulations

Neuroinflammation is often associated with poor functional recovery and may contribute to or initiate the development of severe neurological disorders, such as epilepsy, Parkinson's disease or Alzheimer's disease. Ibuprofen (IBU), being one of the most commonly used non-steroidal anti-inflammatory drugs, is known to possess neuroprotective activity and serve as a promising therapeutic for the treatment of neuroinflammation. In this study, the potential of an IBU-loaded poly(3,4-ethylenedioxypyrrole) (PEDOP) matrix has been assessed as a neural interface material with an aim to control astrocyte activation and suppress neuroinflammation in vitro. Three types of drug immobilization protocols were investigated, leading to the fabrication of IBU-loaded PEDOP matrices exhibiting a broad spectrum of electrical characteristics, drug release profiles, as well as biological responses. Among all investigated PEDOP formulations, PEDOP matrices formed through a three-step immobilization protocol exhibited the highest charge storage capacity (30 ± 1 mC/cm²) as well as a double layer capacitance of 645.0 ± 51.1 µF, associated with a relatively enlarged surface area. Demonstrating a total drug loading capacity of 150 µg/ml and a release rate constant of 0.15 1/h, this coating formulation may be employed as a safe electrical conducting drug eluting system.

Chitosan-Coated Alginate Nanoparticles Enhanced Absorption Profile of Insulin Via Oral Administration

BACKGROUND

In this study, four nanoparticle formulations (F1 to F4) comprising varying ratios of alginate, Pluronic F-68 and calcium chloride with a constant amount of insulin and chitosan as a coating material were prepared using polyelectrolyte complexation and ionotropic gelation methods to protect insulin against enzymatic degradation.

METHODS

This study describes the formulation design, optimisation, characterisation and evaluation of insulin concentration via oral delivery in rats. A reversed-phase high-performance liquid chromatography (HPLC) method was developed and validated to quantify insulin concentration in rat plasma. The proposed method produced a linear response over the concentration range of 0.39 to 50 µg/ml.

RESULTS

In vitro release study showed that dissolution of insulin in simulated gastric juice of pH 1.2 was prevented by alginate core and chitosan coating but rapidly released in simulated intestinal fluid (pH 6.8). Additionally, Formulation 3 (F3) has a particle size of 340.40 ± 2.39 nm with narrow uniformity exhibiting encapsulation efficiency (EE) of 72.78 ± 1.25 % produced highest absorption profile of insulin with a bioavailability of 40.23 ±1.29% and reduced blood glucose after its oral administration in rats.

CONCLUSION

In conclusion, insulin oral delivery system containing alginate and chitosan as a coating material has the ability to protect the insulin from enzymatic degradation thus enhance its absorption in the intestine. However, more work should be done for instance to involve human study to materialise this delivery system for human use.

Nanoengineering of Gold Nanoparticles: Green Synthesis, Characterization, and Applications

The fundamental aspects of the manufacturing of gold nanoparticles (AuNPs) are discussed in this review. In particular, attention is devoted to the development of a simple and versatile method for the preparation of these nanoparticles. Eco-friendly synthetic routes, such as wet chemistry and biosynthesis with the aid of polymers, are of particular interest. Polymers can act as reducing and/or capping agents, or as soft templates leading to hybrid nanomaterials. This methodology allows control of the synthesis and stability of nanomaterials with novel properties. Thus, this review focus on a fundamental study of AuNPs properties and different techniques to characterize them, e.g., Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), UV-Visible spectroscopy, Dynamic Light Scattering (DLS), X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy, Small-angle X-Ray Scattering (SAXS), and rheology. Recently, AuNPs obtained by “green” synthesis have been applied in catalysis, in medicine, and as antibacterials, sensors, among others.

Ultra-low voltage triggered release of an anti-cancer drug from polypyrrole nanoparticles

We have synthesized polypyrrole nanoparticles using three different oxidizing agents (hydrogen peroxide, chloroauric acid and ferric chloride) and shown that films assembled from these nanoparticles have significantly different drug release profiles. When ferric chloride is used as the oxidizing agent, it is possible to release drugs at voltages as low as -0.05 V, almost an order of magnitude lower than typically used voltages. These ultra-low voltage responsive nanoparticles widen the window of operation of conducting polymers and enable delivery of redox active drugs. As an example, we have shown pulsed release of the chemotherapeutic methotrexate at voltages as low as -0.075 V, demonstrating the potential application of these nanoparticles in cancer treatment. We have also verified the anti-tumor efficacy of the released drug using PC12 cell cultures.

Electroactive biomaterials: Vehicles for controlled delivery of therapeutic agents for drug delivery and tissue regeneration

Electrical stimulation for delivery of biochemical agents such as genes, proteins and RNA molecules amongst others, holds great potential for controlled therapeutic delivery and in promoting tissue regeneration. Electroactive biomaterials have the capability of delivering these agents in a localized, controlled, responsive and efficient manner. These systems have also been combined for the delivery of both physical and biochemical cues and can be programmed to achieve enhanced effects on healing by establishing control over the microenvironment. This review focuses on current state-of-the-art research in electroactive-based materials towards the delivery of drugs and other therapeutic signalling agents for wound care treatment. Future directions and current challenges for developing effective electroactive approach based therapies for wound care are discussed.

Electrically controlled release of insulin using polypyrrole nanoparticles

Conducting polymers present an opportunity for developing programmable, adjustable, spatially, and temporally controllable drug delivery systems. While several small molecule drugs have been released from thin conductive polymeric films successfully, delivering large molecule therapeutics, such as polypeptides and nucleic acids, has remained a significant challenge. Poor drug loading (∼ng cm-2) of thin films coupled with film instability has, in many cases, made conducting polymer films refractory to clinical development. To address these limitations, we have utilized conductive polymer nanoparticulate backbones to controllably release insulin, a high molecular weight, clinically relevant polypeptide. We find that the interaction between insulin and the polymer scaffold can be described by a simple Langmuir-type adsorption model. By modifying the ratio of the amount of nanoparticles to the amount of insulin, we have obtained drug loading percentages estimated to be as high as 51 wt% percent. In vivo experiments in mice confirmed retained bioactivity of the released insulin after electrical stimulation.

Online Spectroscopic Monitoring of Drug Release Kinetics from Nanostructured Dual-Stimuli-Responsive Conducting Polymer

PURPOSE

The potential of electrochemical/temperature dual stimuli-responsive conducting polymer to be used as general drug delivery systems. It allows on-demand release of incorporated drug is kinetically investigated in real time.

METHODS

Online spectroscopic monitoring was used to investigate the electrochemically/thermally controlled release behavior of a model drug (naproxen) from drug-doped polypyrrole (DDPPy) film. Avrami's equation has been used to study the kinetics and further analyzing has been carried out using the Arrhenius and the Eyring equations. Furthermore, drug release behavior, with two other electrochemical techniques was investigated.

RESULTS

It was observed both temperature and electrical stimuli increase the rate of release while electrical potential has a greater effect as revealed in the values of release rate constant (from 0.0068 to 0.018 min^-1 at 37°C). It was also shown that a linear relationship exists between the applied electrical potentials and release activation parameters.

CONCLUSION

The electronic properties of the conducting polymer has an important role in release kinetics, there might be a single mechanism with the same limiting step. In addition, it was demonstrated the rate of drug release from DDPPy dramatically depends on the amounts as well as modes of applying potential which provides enhanced control of drug-release kinetics which can be accelerated or even sustained.

Stimuli-Responsive Delivery of Therapeutics for Diabetes Treatment

Diabetic therapeutics, including insulin and glucagon-like peptide 1 (GLP-1), are essential for diabetic patients to regulate blood glucose levels. However, conventional treatments that are based on subcutaneous injections are often associated with poor glucose control and a lack of patient compliance. In this review, we focus on the different stimuli-responsive systems to deliver therapeutics for diabetes treatment to improve patient comfort and prevent complications. Specifically, the pH-responsive systems for oral drug delivery are introduced first. Then, the closed-loop glucose-responsive systems are summarized based on different glucose-responsive moieties, including glucose oxidase (GOx), glucose binding protein (GBP), and phenylboronic acid (PBA). Finally, the on-demand delivery systems activated by external remote triggers are also discussed. We conclude by discussing advantages and limitations of current strategies, as well as future opportunities and challenges in this area.

Amoxicillin functionalized gold nanoparticles reverts MRSA resistance

In this study, we have described the biosynthesis of biocompatible gold nanoparticles (GNPs) from aqueous extract of the aerial parts of a pteridophyte, "Adiantum philippense" by microwave irradiation and its surface functionalization with broad spectrum beta lactam antibiotic, amoxicillin (Amox). The functionalization of amoxicillin on GNPs (GNP-Amox) was carried out via electrostatic interaction of protonated amino group and thioether moiety mediated attractive forces. The synthesized GNPs and GNP-Amox were physicochemically characterized. UV-Vis spectroscopy, Zeta potential, XRD, FTIR and SERS (surface enhanced raman spectra) results confirmed the loading of Amox into GNPs. Loading of Amox to GNPs reduce amoxicillin cytotoxicity, whereas GNPs were found to be nontoxic to mouse fibroblast cell line (L929) as evident from MTT and acridine orange/ethidium bromide (AO/EtBr) live/dead cell assays. The GNP-Amox conjugates demonstrated enhanced broad-spectrum bactericidal activity against both Gram-positive and Gram-negative bacteria. Furthermore, in-vitro and in-vivo assays of GNP-Amox revealed potent anti-MRSA activity and improved the survival rate. This indicates the subversion of antibiotic resistance mechanism by overcoming the effect of high levels of β-lactamase produced by methicillin resistant Staphylococcus aureus (MRSA). Taken together, this study demonstrates the positive attributes from GNP-Amox conjugates as a promising antibacterial therapeutic agent against MRSA as well as other pathogens.

Peripheral Nerve Regeneration Strategies: Electrically Stimulating Polymer Based Nerve Growth Conduits

Treatment of large peripheral nerve damages ranges from the use of an autologous nerve graft to a synthetic nerve growth conduit. Biological grafts, in spite of many merits, show several limitations in terms of availability and donor site morbidity, and outcomes are suboptimal due to fascicle mismatch, scarring, and fibrosis. Tissue engineered nerve graft substitutes utilize polymeric conduits in conjunction with cues both chemical and physical, cells alone and or in combination. The chemical and physical cues delivered through polymeric conduits play an important role and drive tissue regeneration. Electrical stimulation (ES) has been applied toward the repair and regeneration of various tissues such as muscle, tendon, nerve, and articular tissue both in laboratory and clinical settings. The underlying mechanisms that regulate cellular activities such as cell adhesion, proliferation, cell migration, protein production, and tissue regeneration following ES is not fully understood. Polymeric constructs that can carry the electrical stimulation along the length of the scaffold have been developed and characterized for possible nerve regeneration applications. We discuss the use of electrically conductive polymers and associated cell interaction, biocompatibility, tissue regeneration, and recent basic research for nerve regeneration. In conclusion, a multifunctional combinatorial device comprised of biomaterial, structural, functional, cellular, and molecular aspects may be the best way forward for effective peripheral nerve regeneration.