Degradation of hydrogel beads for the detection of serum bicarbonate levels for the diagnosis of metabolic alkalosis at the point of care.

In this work, we present a novel point-of-care hydrogel-based diagnostic device for the rapid detection of elevated bicarbonate levels in serum for the diagnosis of mild to severe cases of metabolic alkalosis. Our system consists of hydrogel beads composed of calcium alginate and the nonionic polymer dextran. This assay utilizes the reaction of sodium bicarbonate and citric acid to produce citrate, a metal chelator capable of competitively binding to calcium cations in the gel matrix to trigger hydrogel degradation. This results in successful detection of elevated bicarbonate concentrations in less than one hour. Specifically, critically high bicarbonate concentrations of 50, 45, and 40 mmol L-1 in human serum were detected in as little as 10, 15, and 20 min, respectively. To demonstrate the assay's feasibility for use in resource-limited settings, we developed a simple electronic device that achieved similar results and could be used by untrained individuals with no lab equipment and minimal power. To our knowledge, this is the first demonstration of the use of nonionic polymers to synthesize and improve the morphology of calcium alginate hydrogel beads using a simple processing method that involves minimal labor and equipment. The simplified bead synthesis protocol combined with the user-friendly device allows for the rapid detection of metabolic alkalosis at the point of care.

Combination of the lateral-flow immunoassay with multicolor gold nanorod etching for the semi-quantitative detection of digoxin.

We are the first to combine the lateral-flow immunoassay (LFA) with gold nanorod (GNR) etching to achieve a multicolor readout where the color produced was correlated with digoxin concentrations in human serum in the relevant range for therapeutic drug monitoring of 0.5-3.0 ng mL-1.

Application of the aqueous two-phase system and nanozyme signal enhancement for the improved detection of Plasmodium lactate dehydrogenase in serum.

Malaria is an infectious disease that can cause severe sickness and death if not diagnosed and treated in a timely manner. The current gold standard technique for malaria diagnosis is microscopy, which requires a dedicated laboratory setting and trained personnel and can have a long time to result. These requirements can be alleviated using paper-based diagnostic devices that enable rapid and inexpensive diagnosis at the point of care, which can allow patients to receive treatment before their symptoms progress when used for early detection of diseases. The lateral-flow immunoassay (LFA) is one such device, but currently available LFAs are susceptible to false negative results caused by low parasite density. To improve sensitivity and detection, we utilized the aqueous two-phase system (ATPS) to concentrate and purify the sample, and nanozyme signal enhancement to increase the intensity of the visible signal on the test strip. We were able to achieve a limit of detection (LOD) of 0.01 ng/mL for the malaria biomarker Plasmodium lactate dehydrogenase (pLDH) in human serum using a multi-step assay combining the LFA format with the ATPS and nanozyme signal enhancement.

On-demand nanozyme signal enhancement at the push of a button for the improved detection of SARS-CoV-2 nucleocapsid protein in serum.

We developed an innovative 3D printed casing that incorporates a lateral-flow immunoassay, dehydrated signal enhancement reagents, and a sealed buffer chamber. With only the push of a button for signal enhancement, our device detected the SARS-CoV-2 N-protein in 40 min at concentrations as low as 0.1 ng mL-1 in undiluted serum.

Novel Zinc / Tungsten Carbide Nanocomposite as Bioabsorbable Implant.

There is a lack of bioabsorbable materials with adequate mechanical strength suitable for implant applications that provide temporary support while tissue integrity is restored, especially for pediatric applications. Bioabsorbable metals have emerged as an attractive choice due to their combination of strength, ductility, and biocompatibility in vivo. Zinc has shown great promise as a bioabsorbable metal, but the weak mechanical properties of pure zinc limit its application as an implant material. This study investigates zinc-tungsten carbide (Zn-WC) nanocomposite as a novel material for bioabsorbable metallic implants. Ultrasound-assisted powder compaction was used to fabricate Zn-WC nanocomposites. This study includes the material characterization of microstructure, microhardness, and degradability. Results showed that tungsten carbide nanoparticles enhanced the mechanical properties of Zn, and maintained the favorable corrosion rate of pure Zn. These results encourage further investigation of Zn-WC nanocomposites for biomedical applications with the ultimate goal of creating safe and efficacious bioabsorbable metallic implants for many clinical applications.

Evaluation of a shape memory implant abutment system: An up to 6-month pilot clinical study.

STATEMENT OF PROBLEM: Screw- and cement-based retention mechanisms are used to attach prostheses to dental implants; however, each approach can lead to clinical complications such as crown fracturing or peri-implantitis. A novel abutment and prosthesis retention system has been engineered to achieve the esthetics and retention force of cement-based fixation while maintaining the retrievability of screw-retained restorations. PURPOSE: The purpose of this pilot clinical study was to evaluate the effectiveness of this innovative retention system on posterior tooth restorations. MATERIAL AND METHODS: This clinical study, with up to 6 months of follow-up, included 8 participants with posterior osseointegrated implants who met the eligibility criteria to receive the abutment and shape memory sleeve. Radiographs were used to evaluate crown seating. Crown stability was measured using the Periotest, and occlusal analysis was performed using the Tekscan system and shimstock. Peri-implant health was evaluated by probing, and the plaque and gingival indices were recorded. In addition, patient-reported outcomes were recorded. RESULTS: Minimal differences were observed between baseline and endpoint assessment of the plaque and gingival indices, probing depth, and proximal and occlusal contacts. There were no patient-reported problems or complaints about discomfort. The overall peri-implant health remained unchanged from the baseline evaluations for all participants. Proximal contact around the restoration was present at the baseline and at the conclusion of the study for 7 of the participants. Occlusal contact was observed to be either light (5 participants) or holding (3 participants). In addition, visual inspection of retrieved crowns revealed clean surfaces free of macroparticle ingress, and bacterial accumulation at the coping-abutment interface was not detected. CONCLUSIONS: The safety and efficacy findings of this pilot clinical study suggest that this new shape memory alloy-based retention system may provide a suitable alternative for implant prosthodontics. The retention system allowed for easy prosthesis seating and retrieval.

Evaluation of the wear and retention performance of a shape-memory alloy abutment system after 6 months of clinical use.

STATEMENT OF PROBLEM: A nitinol sleeve that uses shape memory to rapidly unlock dental restorations from implant abutments has been developed to allow prosthesis removal for assessment and maintenance, and clinical treatment has been promising. However, objective studies that evaluate the wear and retention performance after short-term clinical use are lacking. PURPOSE: The purpose of this clinical study was to evaluate the wear and retention performance of a shape-memory abutment system after 6 months of clinical use. MATERIAL AND METHODS: Shape-memory alloy sleeves on posterior osseointegrated implants were retrieved after 6 months of clinical use. Scanning electron microscopy (SEM) was used to evaluate the surfaces of the retention sleeve's arms for wear. Uniaxial tensile testing was performed to measure the change in retention force after clinical use. Average retention values of the shape-memory abutment system were compared with previously reported in vitro retention values for definitive and interim cements used in titanium abutment and coping assemblies by using the Welch t test. RESULTS: No evidence of wear, fracture, or chipping was observed during SEM analysis on the shape-memory alloy sleeves. Additionally, no statistically significant difference was found in the median retention force for new (484.5 N) and clinically retrieved (476 N) nitinol sleeve specimens. Compared with a commercially available resin cement, the mean retention force for the control sleeves (480 ±37 N) was higher than that for the freshly cemented specimens (336.3 ±188 N). After 5000 cycles of compressive loads, the mean retention force for cement specimens decreased (209.4 ±83 N), while the clinical sleeves (476 ±50 N) remained unchanged. CONCLUSIONS: According to the results of this study, after 6 months of clinical use, the engaging surfaces of the shape-memory alloy sleeve did not show signs of wear, and the retention force was unchanged.

Treating an edentulous mandible with an implant-supported prosthesis with a shape-memory alloy abutment system.

This clinical report describes a treatment protocol for completely edentulous patients using digital implant planning for an all-on-4 treatment of both the maxilla and mandible as well as the use of a shape-memory alloy retention system to secure a complete-arch restoration to the mandible.

Changes in mechanical properties, surface morphology, structure, and composition of Invisalign material in the oral environment.

INTRODUCTION: The mechanical properties of Invisalign material have rarely been explored because of the inaccessibility of the patent-protected raw material. The purpose of this study was to systematically evaluate the Invisalign thermoformed aligner material before and after clinical application, including mechanical properties, surface morphology, internal structure, and chemical composition changes. METHODS: Twenty sets of "as-received" (0-week) and retrieved (2-week; worn for 2 weeks, 20 ± 2 hours per day) Invisalign aligners were randomly collected from 4 different patients. Tensile tests, stress relaxation, and creep tests were carried out with a dynamic mechanical analyzer to characterize the changes in the mechanical properties of this material, Fourier transform infrared spectroscopy was used to capture the molecular changes on the surface of these aligners, scanning electron microscopy and transmission electron microscopy were used to observe the changes in surface morphology and internal structure, and scanning transmission electron microscopy-energy dispersive x-ray analysis was used to detect any changes in the chemical composition of this material before and after clinical application. RESULTS: The elastic modulus of 0-week and 2-week samples were 842 ± 63 MPa and 806 ± 19 MPa, respectively, with no significant difference. In addition, the relative stress after stress relaxation of 2 hours was 19.89 ± 2.25% and 15.91 ± 6.04% for 0-week and 2-week groups, respectively, with no significant difference. Scanning electron microscopy observations showed voids and signs of delamination on the surface of the 2-week samples, and scanning transmission electron microscopy-energy dispersive x-ray analysis indicated the possible release of trace elements during clinical use, such as aluminum. Results of Fourier transform infrared spectroscopy analysis, and transmission electron microscopy observations were quite stable, indicating that the molecular structure on the surface and the internal structure of this material were relatively stable under the oral environment. CONCLUSIONS: The surface morphology showed some defects after the clinical use of 2 weeks; however, there was no significant difference in mechanical properties. Trace elements may release out during clinical use and may pose a specific danger to allergic patients.

Automation of Biomarker Preconcentration, Capture, and Nanozyme Signal Enhancement on Paper-Based Devices.

Infectious diseases remain one of the leading causes of deaths in developing countries because of a lack of basic sanitation, healthcare clinics, and centralized laboratories. Paper-based rapid diagnostic tests, such as the lateral-flow immunoassay (LFA), provide a promising alternative to the traditional laboratory-based tests; however, they typically suffer from having a poor sensitivity. Biomarker preconcentration and signal enhancement are two common methods to improve the sensitivity of paper-based assays. While effective, these methods often require multiple liquid handling steps which are not ideal for use by untrained personnel in a point-of-care setting. Our lab previously discovered the phenomenon of an aqueous two-phase system (ATPS) separating on paper, which allowed for the seamless integration of concentration and detection of biomarkers on the LFA. In this work, we have extended the functionality of an ATPS separating on paper to automate the sequential delivery of signal enhancement reagents in addition to concentrating biomarkers. The timing of reagent delivery was controlled by changing the initial composition of the ATPS. We applied this technology to automate biomarker concentration and nanozyme signal enhancement on the LFA, resulting in a 30-fold improvement in detection limit over the conventional LFA when detecting Escherichia coli, all while maintaining a single application step.

Harnessing the versatility of PLGA nanoparticles for targeted Cre-mediated recombination.

Ligand-dependent Cre recombinases are pivotal tools for the generation of inducible somatic mutants. This method enables spatial and temporal control of gene activity through tamoxifen administration, providing new avenues for studying gene function and establishing animal models of human diseases. While this paved the way for developmental studies previously deemed impractical, the generation of tissue-specific transgenic mouse lines can be time-consuming and costly. Herein, we design a 'smart', biocompatible, and biodegradable nanoparticle system encapsulated with tamoxifen that is actively targeted to specific cell types in vivo through surface conjugation of antibodies. We demonstrate that these nanoparticles bind to cells of interest and activate Cre recombinase, resulting in tissue-specific Cre activation. This system provides a versatile, yet powerful approach to induce recombination in a ubiquitious Cre system for various biomedical applications and sets the stage for a time- and cost-effective strategy of generating new transgenic mouse lines.

A one-pot, isothermal DNA sample preparation and amplification platform utilizing aqueous two-phase systems.

Infectious diseases remain one of the major causes of death worldwide in developing countries. While screening via conventional polymerase chain reaction (PCR) is the gold standard in laboratory testing, its limited applications at the point-of-care have prompted the development of more portable nucleic acid detection systems. These include isothermal DNA amplification techniques, which are less equipment-intensive than PCR. Unfortunately, these techniques still require extensive sample preparation, limiting user accessibility. In this study, we introduce a novel system that combines thermophilic helicase-dependent amplification (tHDA) with a Triton X-100 micellar aqueous two-phase system (ATPS) to achieve cell lysis, lysate processing, and enhanced nucleic acid amplification in a simple, one-step process. The combined one-pot system was able to amplify and detect a target gene from whole-cell samples containing as low as 102 cfu/mL, and is the first known application of ATPSs to isothermal DNA amplification. This system's ease-of-use and sensitivity underlie its potential as a point-of-care diagnostic platform to detect for infectious diseases. Graphical abstract ᅟ.

Effects of an etching solution on the adhesive properties and surface microhardness of zirconia dental ceramics.

STATEMENT OF PROBLEM: Conventional approaches to adhesive bonding are not applicable to zirconia restorations. Recently, an etching solution, Zeta Etching Solution (ZES), has been introduced for etching the surface of zirconia. The effects of this etching solution on the bond strength and mechanical properties of zirconia are unknown. PURPOSE: The purpose of this in vitro study was to examine the effects of ZES on the bond strength and surface hardness of zirconia. MATERIAL AND METHODS: Two different types of partially stabilized tetragonal polycrystalline zirconia (TZP), Prettau zirconia (group P) and anterior Prettau (group AP), were evaluated with and without ZES etching. Each group was bonded to a zirconia substrate by using an adhesive resin cement. After 24 hours of storage in distilled water, the bond strength of the zirconia was analyzed. Vickers hardness was determined by using a microhardness tester. Scanning electron microscopy was used to analyze the surface microstructure and determine the mode of failure for each specimen. Results were analyzed and compared using 1-way ANOVA and Student t tests (α=.05). RESULTS: Scanning electron microscopy analysis showed that etching the surface of zirconia with ZES etching solution for 60 minutes changed the morphological characteristics and microstructure of zirconia, making the surface more irregular. The changes were more pronounced for AP specimens. Etching with ZES significantly increased the shear bond strength of zirconia (P<.05) in AP specimens. The bond strength of Prettau (P group) specimens after ZES etching did not increase significantly (P>.05). An adhesive failure mode was observed for P zirconia specimens, whereas zirconia specimens exhibited a cohesive mode of failure. No significant decrease (P>.05) was observed in the mean Vickers hardness numbers. CONCLUSIONS: Within the limitations of this in vitro study, it was concluded that etching in ZES for 30 minutes significantly enhanced the shear bond strength of highly translucent anterior Prettau (AP) zirconia restorations. Moreover, etching with ZES did not adversely affect the surface hardness of the zirconia specimens tested.

Alginate/hyaluronic acid hydrogel delivery system characteristics regulate the differentiation of periodontal ligament stem cells toward chondrogenic lineage.

Cartilage tissue regeneration often presents a challenging clinical situation. Recently, it has been shown that Periodontal Ligament Stem Cells (PDLSCs) possess high chondrogenic differentiation capacity. In this study, we developed a stem cell delivery system based on alginate/hyaluronic acid (HA) loaded with TGF-ß1 ligand, encapsulating PDLSCs; and investigated the chondrogenic differentiation of encapsulated cells in alginate/HA hydrogel microspheres in vitro and in vivo. The results showed that PDLSCs, as well as human bone marrow mesenchymal stem cells (hBMMSCs), as the positive control, were stained positive for both toluidine blue and alcian blue staining, while exhibiting high levels of gene expression related to chondrogenesis (Col II, Aggrecan and Sox-9), as assessed via qPCR. The quantitative PCR analyses exhibited that the chondrogenic differentiation of encapsulated MSCs can be regulated by the modulus of elasticity of hydrogel delivery system, confirming the vital role of the microenvironment, and the presence of inductive signals for viability and differentiation of MSCs. In vivo, histological and immunofluorescence staining for chondrogenic specific protein markers confirmed ectopic cartilage-like tissue regeneration inside transplanted hydrogels. PDLSCs presented significantly greater capability for chondrogenic differentiation than hBMMSCs (P < 0.05). Altogether, our findings confirmed that alginate/HA hydrogels encapsulating PDLSCs are a promising candidate for cartilage regeneration.

Clinical application of a shape memory implant abutment system.

An innovative abutment system has recently been developed to address the well-known limitations of screw- and cement-retained implant restorations. This abutment system offers retrievability by replacing the cement layer with a precision-engineered nickel-titanium sleeve that switches between shapes that lock and unlock the prosthesis. The avoidance of cement precludes cement-related periimplant complications, while the elimination of occlusal screw access holes may enable predictable control over occlusion and improve the structural integrity of the prosthesis. By eliminating the need for cement clean up, occlusal access closure, and occlusal adjustments after insertion, the dentist is afforded more time to attend to the patient's general needs. This paper describes the design rationale for and clinical treatment using this novel abutment system.

Dental and orofacial mesenchymal stem cells in craniofacial regeneration: The prosthodontist's point of view.

Of the available regenerative treatment options, craniofacial tissue regeneration using mesenchymal stem cells (MSCs) shows promise. The ability of stem cells to produce multiple specialized cell types along with their extensive distribution in many adult tissues have made them an attractive target for applications in tissue engineering. MSCs reside in a wide spectrum of postnatal tissue types and have been successfully isolated from orofacial tissues. These dental- or orofacial-derived MSCs possess self-renewal and multilineage differentiation capacities. The craniofacial system is composed of complex hard and soft tissues derived from sophisticated processes starting with embryonic development. Because of the complexity of the craniofacial tissues, the application of stem cells presents challenges in terms of the size, shape, and form of the engineered structures, the specialized final developed cells, and the modulation of timely blood supply while limiting inflammatory and immunological responses. The cell delivery vehicle has an important role in the in vivo performance of stem cells and could dictate the success of the regenerative therapy. Among the available hydrogel biomaterials for cell encapsulation, alginate-based hydrogels have shown promising results in biomedical applications. Alginate scaffolds encapsulating MSCs can provide a suitable microenvironment for cell viability and differentiation for tissue regeneration applications. This review aims to summarize current applications of dental-derived stem cell therapy and highlight the use of alginate-based hydrogels for applications in craniofacial tissue engineering.

Brief Report: Human Perivascular Stem Cells and Nel-Like Protein-1 Synergistically Enhance Spinal Fusion in Osteoporotic Rats.

Autologous bone grafts (ABGs) are considered as the gold standard for spinal fusion. However, osteoporotic patients are poor candidates for ABGs due to limited osteogenic stem cell numbers and function of the bone microenvironment. There is a need for stem cell-based spinal fusion of proven efficacy under either osteoporotic or nonosteoporotic conditions. The purpose of this study is to determine the efficacy of human perivascular stem cells (hPSCs), a population of mesenchymal stem cells isolated from adipose tissue, in the presence and absence of NELL-1, an osteogenic protein, for spinal fusion in the osteoporosis. Osteogenic differentiation of hPSCs with and without NELL-1 was tested in vitro. The results indicated that NELL-1 significantly increased the osteogenic potential of hPSCs in both osteoporotic and nonosteoporotic donors. Next, spinal fusion was performed by implanting scaffolds with regular or high doses of hPSCs, with or without NELL-1 in ovariectomized rats (n = 41). Regular doses of hPSCs or NELL-1 achieved the fusion rates of only 20%-37.5% by manual palpation. These regular doses had previously been shown to be effective in nonosteoporotic rat spinal fusion. Remarkably, the high dose of hPSCs+NELL-1 significantly improved the fusion rates among osteoporotic rats up to approximately 83.3%. Microcomputed tomography imaging and quantification further confirmed solid bony fusion with high dose hPSCs+NELL-1. Finally, histologically, direct in situ involvement of hPSCs in ossification was shown using undecalcified samples. To conclude, hPSCs combined with NELL-1 synergistically enhances spinal fusion in osteoporotic rats and has great potential as a novel therapeutic strategy for osteoporotic patients.

Translational aspects of cardiac cell therapy.

Cell therapy has been intensely studied for over a decade as a potential treatment for ischaemic heart disease. While initial trials using skeletal myoblasts, bone marrow cells and peripheral blood stem cells showed promise in improving cardiac function, benefits were found to be short-lived likely related to limited survival and engraftment of the delivered cells. The discovery of putative cardiac 'progenitor' cells as well as the creation of induced pluripotent stem cells has led to the delivery of cells potentially capable of electromechanical integration into existing tissue. An alternative strategy involving either direct reprogramming of endogenous cardiac fibroblasts or stimulation of resident cardiomyocytes to regenerate new myocytes can potentially overcome the limitations of exogenous cell delivery. Complimentary approaches utilizing combination cell therapy and bioengineering techniques may be necessary to provide the proper milieu for clinically significant regeneration. Clinical trials employing bone marrow cells, mesenchymal stem cells and cardiac progenitor cells have demonstrated safety of catheter based cell delivery, with suggestion of limited improvement in ventricular function and reduction in infarct size. Ongoing trials are investigating potential benefits to outcome such as morbidity and mortality. These and future trials will clarify the optimal cell types and delivery conditions for therapeutic effect.

Using an aqueous two-phase polymer-salt system to rapidly concentrate viruses for improving the detection limit of the lateral-flow immunoassay.

The development of point-of-need (PON) diagnostics for viruses has the potential to prevent pandemics and protects against biological warfare threats. Here we discuss the approach of using aqueous two-phase systems (ATPSs) to concentrate biomolecules prior to the lateral-flow immunoassay (LFA) for improved viral detection. In this paper, we developed a rapid PON detection assay as an extension to our previous proof-of-concept studies which used a micellar ATPS. We present our investigation of a more rapid polymer-salt ATPS that can drastically improve the assay time, and show that the phase containing the concentrated biomolecule can be extracted prior to macroscopic phase separation equilibrium without affecting the measured biomolecule concentration in that phase. We could therefore significantly decrease the time of the diagnostic assay with an early extraction time of just 30 min. Using this rapid ATPS, the model virus bacteriophage M13 was concentrated between approximately 2 and 10-fold by altering the volume ratio between the two phases. As the extracted virus-rich phase contained a high salt concentration which destabilized the colloidal gold indicator used in LFA, we decorated the gold nanoprobes with polyethylene glycol (PEG) to provide steric stabilization, and used these nanoprobes to demonstrate a 10-fold improvement in the LFA detection limit. Lastly, a MATLAB script was used to quantify the LFA results with and without the pre-concentration step. This approach of combining a rapid ATPS with LFA has great potential for PON applications, especially as greater concentration-fold improvements can be achieved by further varying the volume ratio. Biotechnol. Bioeng. 2014;111: 2499-2507. © 2014 Wiley Periodicals, Inc.

Effect of TiC Nanoparticles on a Zn-Al-Cu System for Biodegradable Cardiovascular Stent Applications.

Despite being a weaker metal, zinc has become an increasingly popular candidate for biodegradable implant applications due to its suitable corrosion rate and biocompatibility. Previous studies have experimented with various alloy elements to improve the overall mechanical performance of pure Zn without compromising the corrosion performance and biocompatibility; however, the thermal stability of biodegradable Zn alloys has not been widely studied. In this study, TiC nanoparticles were introduced for the first time to a Zn-Al-Cu system. After hot rolling, TiC nanoparticles were uniformly distributed in the Zn matrix and effectively enabled phase control during solidification. The Zn-Cu phase, which was elongated and sharp in the reference alloy, became globular in the nanocomposite. The strength of the alloy, after introducing TiC nanoparticles, increased by 31% from 259.7 to 340.3 MPa, while its ductility remained high at 49.2% elongation to failure. Fatigue performance also improved greatly by adding TiC nanoparticles, increasing the fatigue limit by 47.6% from 44.7 to 66 MPa. Furthermore, TiC nanoparticles displayed excellent phase control capability during body-temperature aging. Without TiC restriction, Zn-Cu phases evolved into dendritic morphologies, and the Al-rich eutectic grew thicker at grain boundaries. However, both Zn-Cu and Al-rich eutectic phases remained relatively unchanged in shape and size in the nanocomposite. A combination of exceptional tensile properties, improved fatigue performance, better long-term stability with a suitable corrosion rate, and excellent biocompatibility makes this new Zn-Al-Cu-TiC material a promising candidate for biodegradable stents and other biodegradable applications.