Multifunctional Dopamine-Based Hydrogel Microneedle Electrode for Continuous Ketone Sensing.

Diabetic ketoacidosis (DKA), a severe complication of type 1 diabetes (T1D), is triggered by production of large quantities of ketone bodies, requiring patients with T1D to constantly monitor their ketone levels. Here, a skin-compatible hydrogel microneedle (HMN)-continuous ketone monitoring (HMN-CKM) device is reported. The sensing mechanism relies on the catechol-quinone chemistry inherent to the dopamine (DA) molecules that are covalently linked to the polymer structure of the HMN patch. The DA serves the dual-purpose of acting as a redox mediator for measuring the byproduct of oxidation of 3-beta-hydroxybutyrate (ß-HB), the primary ketone bodies; while, also facilitating the formation of a crosslinked HMN patch. A universal approach involving pre-oxidation and detection of the generated catechol compounds is introduced to correlate the sensor response to the ß-HB concentrations. It is further shown that real-time tracking of a decrease in ketone levels of T1D rat model is possible using the HMN-CKM device, in conjunction with a data-driven machine learning model that considers potential time delays.

"Smart" Matrix Microneedle Patch Made of Self-Crosslinkable and Multifunctional Polymers for Delivering Insulin On-Demand.

A transdermal patch that delivers insulin at high glucose concentrations can offer tremendous advantages to ease the concern of safety and improve the quality of life for people with diabetes. Herein, a novel self-crosslinkable and glucose-responsive polymer-based microneedle patch (MN) is designed to deliver insulin at hyperglycemia. The microneedle patch is made of hyaluronic acid polymers functionalized with dopamine and 4-amino-3-fluorophenylboronic acid (AFBA) that can be quickly crosslinked upon mixing of the polymer solutions in the absence of any chemicalcrosslinking agents or organic solvents. The catechol groups in the dopamine (DA) units form covalent crosslinkages among themselves by auto-oxidation and dynamic crosslink with phenylboronic acid (PBA) via complexation. The reversible crosslinkages between catechol and boronate decrease with increasing glucose concentration leading to higher swelling and faster insulin release at hyperglycemia as compared to euglycemia. Such superior glucose-responsive properties are demonstrated by in vitro analyses and in vivo efficacy studies. The hydrogel polymers also preserve native structure and bioactivity of insulin, attributable to the interaction of hyaluronic acid (HA) with insulin molecules, as revealed by experiments and molecular dynamics simulations. The simplicity in the design and fabrication process, and glucose-responsiveness in insulin delivery impart the matrix microneedle (mMN) patch great potential for clinical translation.

A Conductive Hydrogel Microneedle-Based Assay Integrating PEDOT:PSS and Ag-Pt Nanoparticles for Real-Time, Enzyme-Less, and Electrochemical Sensing of Glucose.

Continuous glucose meters (CGMs) have tremendously boosted diabetes care by emancipating millions of diabetic patients' need for repeated self-testing by pricking their fingers every few hours. However, CGMs still suffer from major deficiencies regarding accuracy, precision, and stability. This is mainly due to their dependency on an enzymatic detection mechanism. Here a low-cost hydrogel microneedle (HMN)-CGM assay fabricated using swellable dopamine (DA)-hyaluronic acid (HA) hydrogel for glucose interrogation in dermal interstitial fluid (ISF) is introduced. Platinum and silver nanoparticles are synthesized within the 3D porous hydrogel scaffolds for nonenzymatic electrochemical sensing of the glucose. Incorporation of a highly water dispersible conductive polymer, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) enhances the electrical properties of HMN array, making the patch suitable as the working electrode of the sensor. The in vitro and ex vivo characterization of this newly developed HMN patch is fully studied. The performance of the HMN-CGM for real-time measurement of glucose is also shown using a rat model of type 1 diabetes. The device introduces the first HMN-based assay for tracking important disease biomarkers and expect to pave the way for next generation of polymeric-based sensors.

A Conductive Hydrogel-Based Microneedle Platform for Real-Time pH Measurement in Live Animals.

Conventional microneedles (MNs) have been extensively reported and applied toward a variety of biosensing and drug delivery applications. Hydrogel forming MNs with the added ability to electrically track health conditions in real-time is an area yet to be explored. The first conductive hydrogel microneedle (HMN) electrode that is capable of on-needle pH detection with no postprocessing required is presented here. The HMN array is fabricated using a swellable dopamine (DA) conjugated hyaluronic acid (HA) hydrogel, and is embedded with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) to increase conductivity. The catechol-quinone chemistry intrinsic to DA is used to measure pH in interstitial fluid (ISF). The effect of PEDOT:PSS on the characteristics of the HMN array such as swelling capability and mechanical strength is fully studied. The HMN's capability for pH measurement is first demonstrated using porcine skin equilibrated with different pH solutions ranging from 3.5 to 9. Furthermore, the HMN-pH meter is capable of in vivo measurements with a 93% accuracy compared to a conventional pH probe meter. This HMN technology bridges the gap between traditional metallic electrochemical biosensors and the direct extraction of ISF, and introduces a platform for the development of polymeric wearable sensors capable of on-needle detection.

Hydrogel Microneedle-Assisted Assay Integrating Aptamer Probes and Fluorescence Detection for Reagentless Biomarker Quantification.

Analyzing interstitial fluid (ISF) via microneedle (MN) devices enables patient health monitoring in a minimally invasive manner and in point-of-care settings. However, most MN-based diagnostic approaches require complicated fabrication processes and postprocessing of the extracted ISF or are limited to detection of electrochemically active biomarkers. Here, we show on-needle measurement of target analytes by integrating hydrogel microneedles with aptamer probes as the recognition elements. Fluorescently tagged aptamer probes are chemically attached to the hydrogel matrix using a simple and novel approach, while a cross-linked patch is formed. For reagentless detection, we employ a strand displacement strategy where fluorophore-conjugated aptamers are hybridized with a DNA competitor strand conjugated to a quencher molecule. The assay is utilized for rapid (2 min) measurement of glucose, adenosine triphosphate, l-tyrosinamide, and thrombin ex vivo. Furthermore, the system enables specific and sensitive quantification of rising and falling concentrations of glucose in an animal model of diabetes to track hypoglycemia, euglycemia, and hyperglycemia conditions. Our assay can be applied for rapid measurement of a diverse range of biomarkers, proteins, or small molecules, introducing a generalizable platform for biomolecule quantification, and has the potential to improve the quality of life of patients who are in need of close monitoring of biomarkers of health and disease.

Advances in Nanomedicine Design: Multidisciplinary Strategies for Unmet Medical Needs.

Globally, a rising burden of complex diseases takes a heavy toll on human lives and poses substantial clinical and economic challenges. This review covers nanomedicine and nanotechnology-enabled advanced drug delivery systems (DDS) designed to address various unmet medical needs. Key nanomedicine and DDSs, currently employed in the clinic to tackle some of these diseases, are discussed focusing on their versatility in diagnostics, anticancer therapy, and diabetes management. First-hand experiences from our own laboratory and the work of others are presented to provide insights into strategies to design and optimize nanomedicine- and nanotechnology-enabled DDS for enhancing therapeutic outcomes. Computational analysis is also briefly reviewed as a technology for rational design of controlled release DDS. Further explorations of DDS have illuminated the interplay of physiological barriers and their impact on DDS. It is demonstrated how such delivery systems can overcome these barriers for enhanced therapeutic efficacy and how new perspectives of next-generation DDS can be applied clinically.

"Smart" Composite Microneedle Patch Stabilizes Glucagon and Prevents Nocturnal Hypoglycemia: Experimental Studies and Molecular Dynamics Simulation.

Hypoglycemia is a major complication associated with insulin therapy in people with diabetes that could cause life-threatening conditions if untreated. Glucagon, a counter-acting hormone, is thus administered for rescue of severe hypoglycemia. However, due to the instability of glucagon, only limited medications are available for emergency use, which are unsuitable for patients with hypoglycemia unawareness or with the inability to self-administer, especially during sleep (namely, nocturnal hypoglycemia). To prevent unattended and extended hypoglycemia, we designed a "smart" composite microneedle (cMN) patch capable of stabilizing glucagon, sensing hypoglycemia, and delivering glucagon automatically on demand. In this design, native glucagon was encapsulated in glucose-responsive microgels containing a glucagon-stabilizing component rationally selected by molecular dynamics (MD) simulation. A cMN patch was then prepared by incorporating the glucagon microgels with poly(methyl vinyl ether-alt-maleic anhydride) (PMVE-MAH) and poly(ethylene glycol) (PEG) followed by thermal cross-linking. The rationally designed zwitterionic polymer-based microgels preserved the native structure of glucagon and prevented heat-induced fibrillation evidenced by RP-HPLC, circular dichroism, and transmission electron microscopy. MD simulations suggested that the polymeric microgels stabilized glucagon by inhibition of oligomer formation via peptide-polymer noncovalent interactions. The polymer formed multiple hydrogen bonds with the polar and charged amino acid residues of the glucagon molecule, shielding the peptide surface from aggregation. In vivo efficacy studies using streptozotocin-induced type 1 diabetic (T1D) rats demonstrated that the glucagon-loaded cMN patch could prevent hypoglycemia induced by insulin overdose during a 12 h period. The results suggest that this new glucagon "smart" patch may be a promising system for improving the quality of life of those suffering from nocturnal hypoglycemia and hypoglycemia unawareness.

Transdermal delivery of a somatostatin receptor type 2 antagonist using microneedle patch technology for hypoglycemia prevention.

Hypoglycemia is a serious and potentially fatal complication experienced by people with insulin-dependent diabetes. The complication is usually caused by insulin overdose, skipping meals, and/or excessive physical activities. In type 1 diabetes (T1D), on top of impaired pancreatic α-cells, excessive levels of somatostatin from δ-cells further inhibit glucagon secretion to counteract overdosed insulin. Herein, we aimed to develop a microneedle (MN) patch for transdermal delivery of a peptide (PRL-2903) that antagonizes somatostatin receptor type 2 (SSTR2) in α-cells. First, we investigated the efficacy of subcutaneously administered PRL-2903 and identified the optimal dose (i.e., the minimum effective dose) and treatment scheduling (i.e., the best administration time for hypoglycemia prevention) in a T1D rat model. We then designed an MN patch using a hyaluronic acid (HA)-based polymer. The possible effect of the polymer on stabilizing the native structure of PRL-2903 was studied by molecular dynamics (MD) simulations. The results showed that the HA-based polymer could stabilize the PRL-2903 structure by restricting water molecules, promoting intra-molecular H-bonding, and constraining torsional angles of important bonds. In vivo studies with an overdose insulin challenge revealed that the PRL-2903-loaded MN patch effectively increased the plasma glucagon level, restored the counter-regulation of blood glucose concentration, and prevented hypoglycemia. The proposed MN patch is the first demonstration of a transdermal microneedle patch designed to deliver an SSTR2 antagonist for the prevention of hypoglycemia. This counter-regulatory peptide delivery system may be applied alongside with insulin delivery systems to provide a more effective and safer treatment for people with insulin-dependent diabetes.

Highlights on Advancing Frontiers in Tissue Engineering.

The field of tissue engineering continues to advance, sometimes in exponential leaps forward, but also sometimes at a rate that does not fulfill the promise that the field imagined a few decades ago. This review is in part a catalog of success in an effort to inform the process of innovation. Tissue engineering has recruited new technologies and developed new methods for engineering tissue constructs that can be used to mitigate or model disease states for study. Key to this antecedent statement is that the scientific effort must be anchored in the needs of a disease state and be working toward a functional product in regenerative medicine. It is this focus on the wildly important ideas coupled with partnered research efforts within both academia and industry that have shown most translational potential. The field continues to thrive and among the most important recent developments are the use of three-dimensional bioprinting, organ-on-a-chip, and induced pluripotent stem cell technologies that warrant special attention. Developments in the aforementioned areas as well as future directions are highlighted in this article. Although several early efforts have not come to fruition, there are good examples of commercial profitability that merit continued investment in tissue engineering. Impact statement Tissue engineering led to the development of new methods for regenerative medicine and disease models. Among the most important recent developments in tissue engineering are the use of three-dimensional bioprinting, organ-on-a-chip, and induced pluripotent stem cell technologies. These technologies and an understanding of them will have impact on the success of tissue engineering and its translation to regenerative medicine. Continued investment in tissue engineering will yield products and therapeutics, with both commercial importance and simultaneous disease mitigation.

Covalent Antiviral Agents.

Nowadays, many viral infections have emerged and are taking a huge toll on human lives globally. Meanwhile, viral resistance to current drugs has drastically increased. Hence, there is a pressing need to design potent broad-spectrum antiviral agents to treat a variety of viral infections and overcome viral resistance. Covalent inhibitors have the potential to achieve both goals owing to their biochemical efficiency, prolonged duration of action, and the capability to inhibit shallow, solvent-exposed substrate-binding domains. In this chapter, we review the structures, activities, and inhibition mechanisms of covalent inhibitors against severe acute respiratory syndrome coronavirus 2, dengue virus, enterovirus, hepatitis C virus, human immunodeficiency virus, and influenza viruses. We also discuss the application of in silico study in covalent inhibitor design.

Crosslinking Strategies for 3D Bioprinting of Polymeric Hydrogels.

Three-dimensional (3D) bioprinting has recently advanced as an important tool to produce viable constructs that can be used for regenerative purposes or as tissue models. To develop biomimetic and sustainable 3D constructs, several important processing aspects need to be considered, among which crosslinking is most important for achieving desirable biomechanical stability of printed structures, which is reflected in subsequent behavior and use of these constructs. In this work, crosslinking methods used in 3D bioprinting studies are reviewed, parameters that affect bioink chemistry are discussed, and the potential toward improving crosslinking outcomes and construct performance is highlighted. Furthermore, current challenges and future prospects are discussed. Due to the direct connection between crosslinking methods and properties of 3D bioprinted structures, this Review can provide a basis for developing necessary modifications to the design and manufacturing process of advanced tissue-like constructs in future.

Glucose-Responsive Composite Microneedle Patch for Hypoglycemia-Triggered Delivery of Native Glucagon.

Insulin-dependent patients with diabetes mellitus require multiple daily injections of exogenous insulin to combat hyperglycemia. However, administration of excess insulin can lead to hypoglycemia, a life-threatening condition characterized by abnormally low blood glucose levels (BGLs). To prevent hypoglycemia associated with intensive insulin therapy, a "smart" composite microneedle (cMN) patch is developed, which releases native glucagon at low glucose levels. The cMN patch is composed of a photo-crosslinked methacrylated hyaluronic acid (MeHA) microneedle array with embedded multifunctional microgels. The microgels incorporate zwitterionic moieties that stabilize loaded glucagon and phenylboronic acid moieties that provide glucose-dependent volume change to facilitate glucagon release. Hypoglycemia-triggered release of structurally unchanged glucagon from the cMN patch is demonstrated in vitro and in a rat model of type 1 diabetes (T1D). Transdermal application of the patch prevented insulin-induced hypoglycemia in the diabetic rats. This work is the first demonstration of a glucose-responsive glucagon-delivery MN patch for the prevention of hypoglycemia, which has a tremendous potential to reduce the dangers of intensive insulin therapy and improve the quality of life of patients with diabetes and their caregivers.

Glucose regulation by modified boronic acid-sulfobetaine zwitterionic nanogels - a non-hormonal strategy for the potential treatment of hyperglycemia.

We have introduced a non-hormonal hyperglycemia treatment strategy by using an injectable glucose-responsive boronic acid- zwitterionic nanogel. The synthesized system, similar to an artificial liver, is capable of storing/releasing glucose at high/low blood glucose concentrations. In vivo performance revealed that the injection of the nanogels can effectively regulate blood glucose in type 1 diabetic rats for at least 6 hours.

Study of the Interactions of Zwitterions and Carbon Nanotubes by Nonlinear Rheology in an Aqueous Environment.

Aqueous nanocomposite solutions of P(NIPAM) and P(NIPAM- co- N-(3-Sulfopropyl)- N-(methacryloxyethyl)- N,N-dimethylammonium betaine), a zwitterionic monomer with carbon nanotubes (CNT) as filler, were synthesized and characterized rheologically. While the influence of P(NIPAM) content and CNT content can be considered to be relatively minor, the introduction of a zwitterionic monomer (Zw) into the polymer leads to clear rheological traces of strong interactions between zwitterionic moieties and surface moieties on the CNTs, namely, a significantly lower nonlinearity limit and a lower modulus at high Zw contents and a higher modulus at intermediate contents due to adsorption of zwitterionic moieties on the CNT surface as well as a significantly lengthened time for the sample to adjust itself to the applied deformation, suggesting that the adsorbed polymer chains need to reorganize themselves significantly to accommodate to the applied strain γ0.

Effect of a functional polymer on the rheology and microstructure of sodium alginate.

Here, we report on the effect of functional copolymer poly(N-isopropylacrylamide-co-4-vinyl-phenylboronic acid) (NIBA) on the rheology and network structure formed by sodium alginate (SA) through linear and nonlinear viscoelasticity measurements. The hydrogel moduli at pH 3 increased with increasing NIBA addition, while the yield point decreased. Furthermore, these hydrogels showed strain-softening behavior, weak G″-overshoot marking the onset of nonlinearity, and good self-healing properties after large deformation. The zero-strain nonlinearity parameter (Q0) was found to be more sensitive to NIBA-addition than the linear viscoelastic properties. The blends showed a clear peak in the startup test except for SA alone and the peak intensity increased with increasing NIBA-concentration. Finally, based on all data, gelation mechanism and interaction of SA and NIBA will be clarified.

Publisher Correction: Functionalized Non-vascular Nitinol Stent via Electropolymerized Polydopamine Thin Film Coating Loaded with Bortezomib Adjunct to Hyperthermia Therapy.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Publisher Correction: Functionalized Non-vascular Nitinol Stent via Electropolymerized Polydopamine Thin Film Coating Loaded with Bortezomib Adjunct to Hyperthermia Therapy.

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Functionalized Non-vascular Nitinol Stent via Electropolymerized Polydopamine Thin Film Coating Loaded with Bortezomib Adjunct to Hyperthermia Therapy.

Gastrointestinal malignancies have been a tremendous problem in the medical field and cover a wide variety of parts of the system, (i.e. esophagus, duodenum, intestines, and rectum). Usually, these malignancies are treated with palliation with the use of non-vascular nitinol stents. However, stenting is not a perfect solution for these problems. While it can enhance the quality of life of the patient, in time the device will encounter problems such as re-occlusion due to the rapid growth of the tumor. In this study, we propose a functionalization technique using electropolymerization of polydopamine directly onto the nitinol stent struts for the combined application of hyperthermia and chemotherapy. The coating was characterized using FESEM, XPS, and FT-IR. Drug release studies show that facile release of the anticancer drug BTZ from the surface of the polydopamine-coated stent could be achieved by the dissociation between catechol groups of polydopamine and the boronic acid functionality of BTZ in a pH-dependent manner. The anti-cancer property was also evaluated, and cytotoxicity on ESO26 and SNU-5 cancer cell lines were observed. Our results suggest that the introduced approach can be considered as a potential method for therapeutic stent application.

A mussel inspired self-expandable tubular hydrogel with shape memory under NIR for potential biomedical applications.

We engineered a novel shape memory polymer (SMP), a nanocomposite hydrogel containing polydopamine nanospheres (PDNs) as a self-expandable tubular hydrogel under near-infrared (NIR) irradiation. When NIR is applied to the nanocomposite hydrogel, the PDN nanoparticles absorb light, which is locally dissipated as heat to become the driving force for shape transition behavior. Since the fabricated PDN material has good mechanical properties, including rapid self-expandability and good biocompatibility, when developed with good heating properties under (NIR) irradiation, it might be useful for many biomedical applications such as the treatment of coronary artery disease.

On-demand drug release and hyperthermia therapy applications of thermoresponsive poly-(NIPAAm-co-HMAAm)/polyurethane core-shell nanofiber mat on non-vascular nitinol stents.

A functional cover made up of core-shell nanofibers with a unique combination of thermoresponsive polymeric shell and stretchable polymeric core for non-vascular nitinol stents that uses an alternating magnetic field (AMF) to induce heat in the stent for hyperthermia therapy and simultaneously release 5-fluorouracil and/or paclitaxel was designed. Varying the ratios of NIPAAm to HMAAm monomer resulted in different LCST properties for the synthesized copolymer and further utilized for an on-demand drug release. Biocompatibility test using NIH-3T3 fibroblast cells indicates that the composite with drug content is biocompatible and the in-vitro cancer cytotoxicity test using ESO26 and OE21 cancer cells proved that the material shows cancer cytotoxic properties via combination of dual drug and hyperthermia therapy. With this functional material, we propose a tailorable and on-demand drug release with more control that can be employed for a combination drug therapy/single drug therapy combined with hyperthermia therapy for cancer cytotoxicity effect.