Acrylic-Based Materials for Biomedical and Bioengineering Applications

Acrylic-based polymers have been used for many years in biomedical applications because of their versatile properties. Many different polymers belong to this class of polymers, of which a significant number have been approved by the US Food and Drug Administration (FDA) and are frequently used in ophthalmologic devices, orthopaedics, tissue engineering applications and dental applications. The applications of this class of polymers have the potential to be expanded exponentially in the biomedical industry if their properties such as mechanical performance, electrical and/or thermal properties, fluid diffusion, biological behaviour, antimicrobial capacity and porosity can be tailored to specific requirements. Thus, acrylic-based materials have been produced as multicomponent polymeric platforms as interpenetrating polymer networks or in combination with other sophisticated materials such as fibres, nanofibres, carbon nanomaterials such as graphene and its derivatives and/or many other types of nanoparticles in the form of composite or nanocomposite biomaterials. Moreover, in regenerative medicine, acrylic porous supports (scaffolds) need to be structured with the necessary degree, type and morphology of pores by advanced technological fabrication techniques

Acrylic-Based Hydrogels as Advanced Biomaterials

Acrylate based hydrogels are one of the most promising soft biocompatible material platforms that significantly contribute to the delivery of therapeutics, contact lenses, corneal prosthesis, bone cements and wound dressing, and are being explored widely for potential applications in the field of regenerative medicine. A significant number of these materials, which possess excellent water sorption properties, have been supported by the Food and Drug Administration (FDA) of the United States for different applications. Nonetheless, many of their physical and biological properties required for certain biomedical and bioengineering applications are often poor when they are in the hydrated state at the body temperature: tensile/compression performance, water diffusion, antimicrobial activity, antifouling capacity, biological response, porosity for the fabrication of supports or scaffolds for tissue engineering, electrical and/or thermal properties, among other properties. Consequently, new acrylic-based hydrogels have been designed as multicomponent systems such as interpenetrated polymer networks, composites and nanocomposite materials, which have exhibited superior properties able to substantially enhance potential uses of these materials in the biomedical and bioengineering industry

Performance of novel enamel-conditioning calcium-phosphate pastes for orthodontic bonding : an in vitro study

This study aimed to develop remineralizing calcium-phosphate (CaP) etchant pastes for enamel conditioning before bracket bonding and evaluate the bonding performance, failure pattern, and enamel surface integrity post bracket debonding in comparison wit

Dual Network Composites of Poly(vinyl alcohol)-Calcium Metaphosphate/Alginate with Osteogenic Ions for Bone Tissue Engineering in Oral and Maxillofacial Surgery

Despite considerable advances in biomaterials-based bone tissue engineering technologies, autografts remain the gold standard for rehabilitating critical-sized bone defects in the oral and maxillofacial (OMF) region. A majority of advanced synthetic bone substitutes (SBS’s) have not transcended the pre-clinical stage due to inferior clinical performance and translational barriers, which include low scalability, high cost, regulatory restrictions, limited advanced facilities and human resources. The aim of this study is to develop clinically viable alternatives to address the challenges of bone tissue regeneration in the OMF region by developing ‘dual network composites’ (DNC’s) of calcium metaphosphate (CMP)—poly(vinyl alcohol) (PVA)/alginate with osteogenic ions: calcium, zinc and strontium. To fabricate DNC’s, single network composites of PVA/CMP with 10% (w/v) gelatine particles as porogen were developed using two freeze–thawing cycles and subsequently interpenetrated by guluronate-dominant sodium alginate and chelated with calcium, zinc or strontium ions. Physicochemical, compressive, water uptake, thermal, morphological and in vitro biological properties of DNC’s were characterised. The results demonstrated elastic 3D porous scaffolds resembling a ‘spongy bone’ with fluid absorbing capacity, easily sculptable to fit anatomically complex bone defects, biocompatible and osteoconductive in vitro, thus yielding potentially clinically viable for SBS alternatives in OMF surgery

In vitro bond strengths post thermal and fatigue load cycling of sapphire brackets bonded with self-etch primer and evaluation of enamel damage

This in vitro study compares a self-etch primer (SEP) to an etch-and-rinse (EaR) for bonding sapphire brackets by evaluation of the enamel etch-pattern, shear bond strength, amount of remnant adhesive and enamel surface damage following thermal and fatigue cyclic loading. Ceramic (sapphire) brackets were bonded to 80 extracted human premolars using two enamel etching protocols: conventional EaR using 37% phosphoric acid (PA) gel (control), and a SEP (Transbond Plus). Each group was subdivided into two subgroups (n=20 teeth) according to the time of bracket debonding: after 24 h water storage or following 5000 thermo-cycles plus 5000 cycles fatigue loading, to determine the shear bond strength (SBS), adhesive remnant index (ARI score), with scanning electron microscopy (SEM) evaluation of enamel condition. The control subgroups consistently exhibited significantly higher (p<0.05) SBS mean values (23.4-29.8 MPa) than the SEP subgroups (15.1-22.4 MPa) at both bracket debonding time points. However, the SEP subgroups yielded milder etch-patterns and attained SBS values above the minimum requirement range for clinical performance. In addition, the higher SBS of control subgroups was accompanied with higher ARI scores and enamel damage grades than SEP subgroups as confirmed by SEM. Thermocycling and fatigue significantly reduced the SBS of all subgroups, with a non-significant drop in the amount of adhesive residue or enamel damage. The use of SEP can be a suitable alternative to the conventional PA gel for sapphire bracket bonding as it maintains suitable bond strength and has the potential to produce both less remnant adhesive and enamel damage

Resistance of bonded premolars to four artificial ageing models post enamel conditioning with a novel calcium-phosphate paste

Background: This in vitro study compares a novel calcium-phosphate etchant paste to conventional 37% phospho-ric acid gel for bonding metal and ceramic brackets by evaluating the shear bond strength, remnant adhesive and enamel damage following water storage, acid challenge and fatigue loading. Material and Methods: Metal and ceramic brackets were bonded to 240 extracted human premolars using two ena-mel conditioning protocols: conventional 37% phosphoric acid (PA) gel (control), and an acidic calcium-phosphate (CaP) paste. The CaP paste was prepared from ?-tricalcium phosphate and monocalcium phosphate monohydrate powders mixed with 37% phosphoric acid solution, and the resulting phase was confirmed using FTIR. The bonded premolars were exposed to four artificial ageing models to examine the shear bond strength (SBS), adhesive rem-nant index (ARI score), with stereomicroscopic evaluation of enamel damage. Results: Metal and ceramic control subgroups yielded significantly higher (p ? 0.05) SBS (17.1-31.8 MPa) than the CaP subgroups (11.4-23.8 MPa) post all artificial ageing protocols, coupled with higher ARI scores and evidence of enamel damage. In contrast, the CaP subgroups survived all artificial ageing tests by maintaining adequate SBS for clinical performance, with the advantages of leaving unblemished enamel surface and bracket failures at the enamel-adhesive interface. Conclusions: Enamel conditioning with acidic CaP pastes attained adequate bond strengths with no or minimal adhesive residue and enamel damage, suggesting a suitable alternative to the conventional PA gel for orthodontic bonding

Antimicrobial Effectiveness of Calcium Silicate Sealers against a Nutrient-Stressed Multispecies Biofilm

PURPOSE: This study compared the antimicrobial efficacy of calcium silicate sealers (BioRoot RCS and Total Fill BC) and conventional sealers (AH Plus and Tubli-seal) against planktonic bacteria and a nutrient-stressed multispecies biofilm. METHODS: Antimicrobial properties of freshly mixed sealers were investigated using the direct contact test (DCT) and a nutrient-stressed multispecies biofilm comprised of five endodontic strains. Antimicrobial activity was determined using quantitative viable counts and confocal laser scanning microscopy (CLSM) analysis with live/dead staining. The pH of the sealers was analysed over a period of 28 days in Hanks Balanced Salt Solution (HBSS). Analysis of variance (ANOVA) with Tukey tests and the Kruskal-Wallis test were used for data analysis with a significance of 5%. RESULTS: All endodontic sealers exhibited significant antimicrobial activity against planktonic bacteria (p 0.05). CLSM analysis showed that BioRoot RCS and TotalFill BC exhibited significant biofilm inhibition compared to Tubli-seal, AH Plus and the control (p 12). CONCLUSIONS: Calcium silicate sealers exhibited effective antimicrobial properties. This was demonstrated by superior biofilm inhibition capacity and microbial killing, with strong alkalizing activity compared to epoxy-based and zinc oxide-eugenol-based sealers

Ex vivo investigations on bioinspired electrospun membranes as potential biomaterials for bone regeneration.

Objectives: To assess the surface characteristics and composition that may enhance osteoblasts viability on novel electrospun composite membranes (organic polymer/silicon dioxide nanoparticles). Methods: Membranes are composed by a novel polymer blend, the mixture of two hydrophilic copolymers 2-hydroxyethylmethacrylate-co-methylmethacrylate and 2-hydroxyethylacrylate-co-methylacrylate, and they are doped with silicon dioxide nanoparticles. Then the membranes were functionalized with zinc or doxycycline. The membranes were morphologically characterized by atomic force and scanning electron microscopy (FESEM), and mechanically probed using a nanoindenter. Biomimetic calcium phosphate precipitation on polymeric tissues was assessed. Cell viability tests were performed using human osteosarcoma cells. Cells morphology was also studied by FESEM. Data were analyzed by ANOVA, Student-Newman-Keuls and Student t tests (p<0.05). Results: Silica doping of membranes enhanced bioactivity and increased mechanical properties. Membranes morphology and mechanical properties were similar to those of trabecular bone. Zinc and doxycycline doping did not exert changes but it increased novel membranes bioactivity. Membranes were found to permit osteoblasts proliferation. Silica-doping favored cells proliferation and spreading. As soon as 24h after the seeding, cells in silica-doped membranes were firmly attached to experimental tissues trough filopodia, connected to each other. The cells produced collagen and minerals onto the surfaces. Conclusions: Silica nanoparticles enhanced surface properties and osteoblasts viability on electrospun membranes. Clinical significance: The ability of silica-doped matrices to promote precipitation of calcium phosphate, together with their mechanical properties, observed non-toxicity, stimulating effect on osteoblasts and its surface chemistry allowing covalent binding of proteins, offer a potential strategy for bone regeneration applications.This work was supported by the Ministry of Economy and Competitiveness (and European Regional Development Fund [Project MAT2017-85999-P MINECO/AEI/FEDER/UE] and University of Granada Research and Transfer Program

Synthesis of irregular graphene oxide tubes using green chemistry and their potential use as reinforcement materials for biomedical applications

Micrometer length tubes of graphene oxide (GO) with irregular form were synthesised following facile and green metal complexation reactions. These materials were obtained by crosslinking of GO with calcium, zinc or strontium chlorides at three different temperatures (24, 34 and 55°C) using distilled water as solvent for the compounds and following a remarkably simple and low-cost synthetic method, which employs no hazardous substances and is conducted without consumption of thermal or sonic energy. These irregular continuous GO networks showed a very particular interconnected structure by Field Emission Scanning Electron Microscopy with Energy-Disperse X-Ray Spectroscopy for elemental analysis and High-resolution Transmission Electron Microscopy with Scanning Transmission Electron Microscope Dark Field Imaging, and were analysed by Raman Spectroscopy. To demonstrate the potential use of these 3D GO networks as reinforcement materials for biomedical applications, two composites of calcium alginate with irregular tubes of GO and with single GO nanosheets were prepared with the same amount of GO and divalent atoms and analysed. Thus, the dynamic-mechanical modulus of the composites synthesised with the 3D crosslinked GO networks showed a very significant mechanical improvement due to marked microstructural changes confirmed by confocal microscopy, differential scanning calorimetry and Fourier transform infrared spectroscopy