Antimicrobial Peptide-Polymer Conjugates for Dentistry

Current approaches to produce durable biomaterials: Trends in polymeric materials for restorative dentistry applications

Dental caries continues to be a public health issue, especially more evident in underserved populations throughout the U.S. Unfortunately, especially with an aging population, hundreds of thousands of resin composite restorations are replaced each year due to recurring decay and fracture. According to several cohort studies, the average life span of this type of restoration is 10 years or less, depending on the caries risk level of the patient and the complexity of the restorative procedure. Any new material development must depart from the simple restoration of form paradigm, in which the filling is simply inert/biocompatible. This review will discuss novel antibiofilm structures, based on a targeted approach specifically against dysbiotic bacteria. Biofilm coalescence can be prevented by using glycosyl transferase - GTF inhibitors, in a non-bactericidal approach. On the tooth substrate side, MMP-inhibiting molecules can improve the stability of the collagen in the hybrid layer. This review will also discuss the importance of testing the materials in a physiologically relevant environment, mimicking the conditions in the mouth in terms of mechanical loading, bacterial challenge, and the presence of saliva. Ultimately, the goal of materials development is to achieve durable restorations, capable of adapting to the oral environment and resisting challenges that go beyond mechanical demands. That way, we can prevent the unnecessary loss of additional tooth structure that comes with every re-treatment. CLINICAL SIGNIFICANCE: While proper restorative technique and patient education in terms of diet and oral hygiene are crucial factors in increasing the longevity of esthetic direct restorations, materials better able to resist and interact with the conditions of the oral environment are still needed. Reproducing the success of dental amalgams with esthetic materials continues to be the Holy Grail of materials development.

Machine learning enabled design features of antimicrobial peptides selectively targeting peri-implant disease progression

Peri-implantitis is a complex infectious disease that manifests as progressive loss of alveolar bone around the dental implants and hyper-inflammation associated with microbial dysbiosis. Using antibiotics in treating peri-implantitis is controversial because of antibiotic resistance threats, the non-selective suppression of pathogens and commensals within the microbial community, and potentially serious systemic sequelae. Therefore, conventional treatment for peri-implantitis comprises mechanical debridement by nonsurgical or surgical approaches with adjunct local microbicidal agents. Consequently, current treatment options may not prevent relapses, as the pathogens either remain unaffected or quickly re-emerge after treatment. Successful mitigation of disease progression in peri-implantitis requires a specific mode of treatment capable of targeting keystone pathogens and restoring bacterial community balance toward commensal species. Antimicrobial peptides (AMPs) hold promise as alternative therapeutics through their bacterial specificity and targeted inhibitory activity. However, peptide sequence space exhibits complex relationships such as sparse vector encoding of sequences, including combinatorial and discrete functions describing peptide antimicrobial activity. In this paper, we generated a transparent Machine Learning (ML) model that identifies sequence-function relationships based on rough set theory using simple summaries of the hydropathic features of AMPs. Comparing the hydropathic features of peptides according to their differential activity for different classes of bacteria empowered predictability of antimicrobial targeting. Enriching the sequence diversity by a genetic algorithm, we generated numerous candidate AMPs designed for selectively targeting pathogens and predicted their activity using classifying rough sets. Empirical growth inhibition data is iteratively fed back into our ML training to generate new peptides, resulting in increasingly more rigorous rules for which peptides match targeted inhibition levels for specific bacterial strains. The subsequent top scoring candidates were empirically tested for their inhibition against keystone and accessory peri-implantitis pathogens as well as an oral commensal bacterium. A novel peptide, VL-13, was confirmed to be selectively active against a keystone pathogen. Considering the continually increasing number of oral implants placed each year and the complexity of the disease progression, prevalence of peri-implant diseases continues to rise. Our approach offers transparent ML-enabled paths towards developing antimicrobial peptide-based therapies targeting the changes in the microbial communities that can beneficially impact disease progression.

Conjugation of antimicrobial peptides to enhance therapeutic efficacy

The growing prevalence of antimicrobial resistance (AMR) has brought with it a continual increase in the numbers of deaths from multidrug-resistant (MDR) infections. Since the current arsenal of antibiotics has become increasingly ineffective, there exists an urgent need for discovery and development of novel antimicrobials. Antimicrobial peptides (AMPs) are considered to be a promising class of molecules due to their broad-spectrum activities and low resistance rates compared with other types of antibiotics. Since AMPs also often play major roles in elevating the host immune response, the molecules may also be called "host defense peptides." Despite the great promise of AMPs, the majority remain unsuitable for clinical use due to issues of structural instability, degradation by proteases, and/or toxicity to host cells. Moreover, AMP activities in vivo can be influenced by many factors, such as interaction with blood and serum biomolecules, physiological salt concentrations or different pH values. To overcome these limitations, structural modifications can be made to the AMP. Among several modifications, physical and chemical conjugation of AMP to other biomolecules is widely considered an effective strategy. In this review, we discuss structural modification strategies related to conjugation of AMPs and their possible effects on mode of action. The conjugation of fatty acids, glycans, antibiotics, photosensitizers, polymers, nucleic acids, nanoparticles, and immobilization to biomaterials are highlighted.

Shaping the Future of Antimicrobial Therapy: Harnessing the Power of Antimicrobial Peptides in Biomedical Applications

Antimicrobial peptides (AMPs) have emerged as a promising class of bioactive molecules with the potential to combat infections associated with medical implants and biomaterials. This review article aims to provide a comprehensive analysis of the role of antimicrobial peptides in medical implants and biomaterials, along with their diverse clinical applications. The incorporation of AMPs into various medical implants and biomaterials has shown immense potential in mitigating biofilm formation and preventing implant-related infections. We review the latest advancements in biomedical sciences and discuss the AMPs that were immobilized successfully to enhance their efficacy and stability within the implant environment. We also highlight successful examples of AMP coatings for the treatment of surgical site infections (SSIs), contact lenses, dental applications, AMP-incorporated bone grafts, urinary tract infections (UTIs), medical implants, etc. Additionally, we discuss the potential challenges and prospects of AMPs in medical implants, such as effectiveness, instability and implant-related complications. We also discuss strategies that can be employed to overcome the limitations of AMP-coated biomaterials for prolonged longevity in clinical settings.

The germicidal effect, biosafety and mechanical properties of antibacterial resin composite in cavity filling

In recent years, dental resin materials have become increasingly popular for cavity filling. However, these materials can shrink during polymerization, leading to microleakages that enable bacteria to erode tooth tissue and cause secondary caries. As a result, there is great clinical demand for the development of antibacterial resins. The principle of antibacterial resin includes contact killing and filler-release killing of bacteria. For contact killing, quaternary ammonium salts (QACs) and antibacterial peptides (AMPs) can be added. For filler-release killing, chlorhexidine (CHX) and nanoparticles are used. These antibacterial agents are effective against gram-positive bacteria, gram-negative bacteria, fungi, and more. Among them, QACs has a lasting antibacterial effect, and silver nanoparticles even have a certain ability to kill viruses. Biocompatibility-wise, QACs, AMPs, and CHX have low cytotoxicity to cells when added into the resin. However, nanoparticles with smaller particle sizes have higher cytotoxicity. In terms of mechanical properties, QACs, AMPs, and CHX do not negatively affect the resin. However, the addition of magnesium oxide can have a negative impact. This paper reviews the types and antibacterial principles of commonly used antibacterial resins in recent years, evaluates their antibacterial effect, biological safety, and mechanical properties, and provides references for selecting clinical filling materials.

Current antibacterial agents in dental bonding systems: a comprehensive overview

Dental caries is mainly caused by oral biofilm acid, and the most common dental restoration treatment is composite dental restorations. The main cause of failure is secondary caries adjacent to the restoration. Long-term survival of dental materials is improved by the presence of antibacterial agents, which selectively inhibit bacterial growth or survival. Chemical, natural and biomaterials have been studied for their antimicrobial activities and antibacterial bonding agents have been improved. Their usage has been increased to inhibit the growth of invading and residual bacteria in the oral cavity, as biofilm accumulation increases the risk of treatment failure. In this article, the success and applications of antibacterial agents are discussed in dental bonding systems.

Smart dental materials for antimicrobial applications

Smart biomaterials can sense and react to physiological or external environmental stimuli (e.g., mechanical, chemical, electrical, or magnetic signals). The last decades have seen exponential growth in the use and development of smart dental biomaterials for antimicrobial applications in dentistry. These biomaterial systems offer improved efficacy and controllable bio-functionalities to prevent infections and extend the longevity of dental devices. This review article presents the current state-of-the-art of design, evaluation, advantages, and limitations of bioactive and stimuli-responsive and autonomous dental materials for antimicrobial applications. First, the importance and classification of smart biomaterials are discussed. Second, the categories of bioresponsive antibacterial dental materials are systematically itemized based on different stimuli, including pH, enzymes, light, magnetic field, and vibrations. For each category, their antimicrobial mechanism, applications, and examples are discussed. Finally, we examined the limitations and obstacles required to develop clinically relevant applications of these appealing technologies.

Polytrimethylenimines: Highly Potent Antibacterial Agents with Activity and Toxicity Modulated by the Polymer Molecular Weight

Cationic polymers have been extensively investigated as a potential replacement for traditional antibiotics. Here, we examined the effect of molecular weight (MW) on the antimicrobial, cytotoxic, and hemolytic activity of linear polytrimethylenimine (L-PTMI). The results indicate that the biological activity of the polymer sharply increases as MW increases. Thanks to a different position of the antibacterial activity and toxicity thresholds, tuning the MW of PTMI allows one to achieve a therapeutic window between antimicrobial activity and toxicity concentrations. L-PTMI presents significantly higher antimicrobial activity against model microorganisms than linear polyethylenimine (L-PEI) when polymers with a similar number of repeating units are compared. For the derivatives of L-PTMI and L-PEI, obtained through N-monomethylation and partial N,N-dimethylation of linear polyamines, the antimicrobial activity and toxicity were both reduced; however, resulting selectivity indices were higher. Selected materials were tested against clinical isolates of pathogens from the ESKAPE group and Mycobacteria, revealing good antibacterial properties of L-PTMI against antibiotic-resistant strains of Gram-positive and Gram-negative bacteria but limited antibacterial properties against Mycobacteria.

Recent Advances in Antimicrobial Peptide Hydrogels

Advances in the number and type of available biomaterials have improved medical devices such as catheters, stents, pacemakers, prosthetic joints, and orthopedic devices. The introduction of a foreign material into the body comes with a risk of microbial colonization and subsequent infection. Infections of surgically implanted devices often lead to device failure, which leads to increased patient morbidity and mortality. The overuse and improper use of antimicrobials has led to an alarming rise and spread of drug-resistant infections. To overcome the problem of drug-resistant infections, novel antimicrobial biomaterials are increasingly being researched and developed. Hydrogels are a class of 3D biomaterials consisting of a hydrated polymer network with tunable functionality. As hydrogels are customizable, many different antimicrobial agents, such as inorganic molecules, metals, and antibiotics have been incorporated or tethered to them. Due to the increased prevalence of antibiotic resistance, antimicrobial peptides (AMPs) are being increasingly explored as alternative agents. AMP-tethered hydrogels are being increasingly examined for antimicrobial properties and practical applications, such as wound-healing. Here, we provide a recent update, from the last 5 years of innovations and discoveries made in the development of photopolymerizable, self-assembling, and AMP-releasing hydrogels.

Peptides in Dentistry: A Scoping Review

Currently, it remains unclear which specific peptides could be appropriate for applications in different fields of dentistry. The aim of this scoping review was to scan the contemporary scientific papers related to the types, uses and applications of peptides in dentistry at the moment. Literature database searches were performed in the following databases: PubMed/MEDLINE, Scopus, Web of Science, Embase, and Scielo. A total of 133 articles involving the use of peptides in dentistry-related applications were included. The studies involved experimental designs in animals, microorganisms, or cells; clinical trials were also identified within this review. Most of the applications of peptides included caries management, implant osseointegration, guided tissue regeneration, vital pulp therapy, antimicrobial activity, enamel remineralization, periodontal therapy, the surface modification of tooth implants, and the modification of other restorative materials such as dental adhesives and denture base resins. The in vitro and in vivo studies included in this review suggested that peptides may have beneficial effects for treating early carious lesions, promoting cell adhesion, enhancing the adhesion strength of dental implants, and in tissue engineering as healthy promotors of the periodontium and antimicrobial agents. The lack of clinical trials should be highlighted, leaving a wide space available for the investigation of peptides in dentistry.

Shear Bond Strength and Color Stability of Novel Antibacterial Nanofilled Dental Adhesive Resins

Experimental adhesives containing co-doped metaloxide nanoparticles were demonstrated to display strong and long-term antibacterial properties against Streptococcus mutans biofilms. The present study represents an effort to characterize the shear-bond strength (SBS) and color stability (CS) of these novel biomaterials. Experimental adhesives were obtained by dispersing nitrogen and fluorine co-doped titanium dioxide nanoparticles (NF_TiO2, 10%, 20% or 30%, v/v%) into OptiBond Solo Plus (OPTB). Dentin surfaces were wet-polished (600-Grit). Specimens (n = 5/group) of Tetric EvoCeram were fabricated and bonded using either OPTB or experimental (OPTB + NF_TiO2) adhesives. Specimens were stored in water (37 °C) for twenty-four hours (T1), three months (T2), and six months (T3). At T1, T2, or T3, specimens were removed from water storage and were tested for SBS. Disc-shaped specimens (n = 10/group; d = 6.0 mm, t = 0.5 mm) of adhesives investigated were fabricated and subjected to thermocycling (10,000 cycles, 5−55 °C, 15 s dwell time). Specimens’ colors were determined with a VITA Easyshade® V spectrophotometer (after every 1000 cycles). SBS data was analyzed using two-way ANOVA and post-hoc Tukey tests, while CS data was analyzed using one-way ANOVA and post-hoc Tukey tests (α = 0.05). Mean values of SBS ranged from 16.39 ± 4.20 MPa (OPTB + 30%NF_TiO2) to 19.11 ± 1.11 MPa (OPTB), from 12.99 ± 2.53 MPa (OPTB + 30% NF_TiO2) to 14.87 ± 2.02 (OPTB) and from 11.37 ± 1.89 (OPTB + 20% NF_TiO2) to 14.19 ± 2.24 (OPTB) after twenty-four hours, three months, and six months of water storage, respectively. Experimental materials had SBS values that were comparable (p > 0.05) to those from OPTB independently of nanoparticle concentration or time-point considered. Experimental materials with higher NF_TiO2 concentrations had less intense color variations and were more color stable than OPTB even after 10,000 thermocycles. In combination, the results reported have demonstrated that experimental adhesives can establish strong and durable bonds to human dentin while displaying colors that are more stable, thereby suggesting that the antibacterial nanotechnology investigated can withstand the harsh conditions within the oral cavity without compromising the esthetic component of dental restorations.

Influence of the Polymerization Modes on the Methacrylic Acid Release from Dental Light-Cured Materials-In Vitro Study

The study focuses on the problem of lowering the pH around a composite filling concerning the polymerization modes and methacrylic acid release, which may affect not only the oral health but also the whole organism. A total of 90 specimens (30 of each: Filtek Bulk Fill, Evetric and Riva LC) were placed in 90 sterile hermetic polyethene containers with saline and incubated at 37 °C. Ten samples of each material were light-cured for 40 s with one of the three curing modes: full power mode (FPM), ramping mode (RM) and pulse mode (PM). The pH and methacrylic acid release evaluation were performed at the following time points: after 2 h and after 3, 7, 21 and 42 days from the specimen preparation. Regardless of light-curing mode, all used materials were characterized by a gradual elevation in methacrylic acid concentration. Only for Filtek Bulk Fill, increased methacrylic acid release was closely associated with lower pH. The choice of the polymerization mode has no significant influence on the methacrylic acid release. However, further research about composite light-curing is necessary to create the procedure algorithm, reducing the local and systemic complications associated with composite fillings.

Peptide–Polymer Conjugates: A Promising Therapeutic Solution for Drug-Resistant Bacteria

By 2050, it is estimated that 10 million people will die of drug-resistant bacterial infection caused by antibiotic abuse. Antimicrobial peptide (AMP) is widely used to prevent such circumstances, for the positively charged AMPs can kill drug-resistant bacteria by destroying negatively charged bacterial cell membrane, and has excellent antibacterial efficiency and low drug resistance. However, due to the defects in low in vivo stability, easy degradation, and certain cytotoxicity, its practical clinical application is limited. The emergence of peptide–polymer conjugates (PPC) helps AMPs overcome these shortcomings. By combining with functional polymers, the positive charge of AMPs is partially shielded, and its stability and water solubility are improved, so as to prolong the in vivo circulation time of AMPs and reduce its cytotoxicity. At the same time, the self-assembly ability of PPC enables it to assemble into different nanostructures to undertake specific antibacterial tasks. At present, PPC is mainly used in wound dressing, bone tissue repair, antibacterial coating of medical devices, nerve repair, tumor treatment, and oral health maintenance. In this study, we summarize the structure, synthesis methods, and the clinical applications of PPC, so as to present the current challenges and discuss the future prospects of antibacterial therapeutic materials.

Engineering peptide-polymer hybrids for targeted repair and protection of cervical lesions

By 2060, nearly 100 million people in the U.S. will be over age 65 years. One-third of these older adults will have root caries, and nearly 80% will have dental erosion. These conditions can cause pain and loss of tooth structure that interfere with eating, speaking, sleeping, and quality of life. Current treatments for root caries and dental erosion have produced unreliable results. For example, the glass-ionomer-cement or composite-resin restorations used to treat these lesions have annual failure rates of 44% and 17%, respectively. These limitations and the pressing need to treat these conditions in the aging population are driving a focus on microinvasive strategies, such as sealants and varnishes. Sealants can inhibit caries on coronal surfaces, but they are ineffective for root caries. For healthy, functionally independent elders, chlorhexidine varnish applied every 3 months inhibits root caries, but this bitter-tasting varnish stains the teeth. Fluoride gel inhibits root caries, but requires prescriptions and daily use, which may not be feasible for some older patients. Silver diamine fluoride can both arrest and inhibit root caries but stains the treated tooth surface black. The limitations of current approaches and high prevalence of root caries and dental erosion in the aging population create an urgent need for microinvasive therapies that can: (a) remineralize damaged dentin; (b) inhibit bacterial activity; and (c) provide durable protection for the root surface. Since cavitated and non-cavitated root lesions are difficult to distinguish, optimal approaches will treat both. This review will explore the multi-factorial elements that contribute to root surface lesions and discuss a multi-pronged strategy to both repair and protect root surfaces. The strategy integrates engineered peptides, novel polymer chemistry, multi-scale structure/property characterization and predictive modeling to develop a durable, microinvasive treatment for root surface lesions.

Growing Global Research Interest in Antimicrobial Peptides for Caries Management: A Bibliometric Analysis

Objective: Researchers are studying the use of antimicrobial peptides as functional biomaterials to prevent and treat dental caries. This study aims to investigate the global research interest in antimicrobial peptides for caries management. Methods: Two independent investigators systematically searched with keywords ('Caries' OR 'Dental caries') AND ('Antimicrobial peptide' OR 'AMP' OR 'Statherin' OR 'Histatin' OR 'Defensin' OR 'Cathelicidin') on Web of Science, PubMed and Scopus. They removed duplicate publications and screened the titles and abstracts to identify relevant publications. The included publications were summarized and classified as laboratory studies, clinical trials or reviews. The citation count and citation density of the three publication types were compared using a one-way analysis of variance. The publications' bibliometric data were analyzed using the Bibliometrix program. Results: This study included 163 publications with 115 laboratory studies (71%), 29 clinical trials (18%) and 19 reviews (11%). The number of publications per year have increased steadily since 2002. The citation densities (mean ± SD) of laboratory study publications (3.67 ± 2.73) and clinical trial publications (2.63 ± 1.85) were less than that of review articles (5.79 ± 1.27) (p = 0.002). The three publication types had no significant difference in citation count (p = 0.54). Most publications (79%, 129/163) reported the development of a novel antimicrobial peptide. China (52/163, 32%) and the US (29/163, 18%) contributed to 50% (81/163) of the publications. Conclusion: This bibliometric analysis identified an increasing trend in global interest in antimicrobial peptides for caries management since 2002. The main research topic was the development of novel antimicrobial peptides. Most publications were laboratory studies, as were the three publications with the highest citation counts. Laboratory studies had high citation counts, whereas reviews had high citation density.

The Retention Effect of Resin-Based Desensitizing Agents on Hypersensitivity-A Randomized Controlled Trial

Recently, the development of dental materials has increased the availability of various hyperesthesia desensitizers. However, there are no studies on the duration of retreatment in terms of adherence rates. Thus, the adhesion rates of resin-based desensitizers were investigated. We used a conventional desensitizer and a recently developed desensitizer containing calcium salt of 4-methacryloxyethyl trimellitic acid (C-MET) and 10-methacryloyloxydecyl dihydrogen calcium phosphate (MDCP). These colored agents were applied to the surfaces of premolars and molars, and the area was measured from weekly oral photographs. Areas were statistically analyzed and mean values were calculated using 95% confidence intervals. A p-value of <0.05 was considered statistically significant. These rates were significantly higher on the buccal side of the maxilla and lower on the lingual side of the maxilla. In addition, the desensitizer containing C-MET and MDCP displayed significantly higher adhesion rates. It is suggested that this will require monthly follow-ups and reevaluation because both agents cause less than 10% adherence and there is almost no sealing effect after 4 weeks. In addition, the significantly higher adhesion rate of the desensitizer containing C-MET and MDCP indicated that the novel monomer contributed to the improvement in the adhesion ability.

Peptide-Enabled Nanocomposites Offer Biomimetic Reconstruction of Silver Diamine Fluoride-Treated Dental Tissues

Caries is the most ubiquitous infectious disease of mankind, and early childhood caries (ECC) is the most prevalent chronic disease in children worldwide, with the resulting destruction of the teeth recognized as a global health crisis. Recent the United States Food and Drug Administration (FDA) approval for the use of silver diamine fluoride (SDF) in dentistry offers a safe, accessible, and inexpensive approach to arrest caries progression in children with ECC. However, discoloration, i.e., black staining, of demineralized or cavitated surfaces treated with SDF has limited its widespread use. Targeting SDF-treated tooth surfaces, we developed a biohybrid calcium phosphate nanocomposite interface building upon the self-assembly of synthetic biomimetic peptides. Here, an engineered bifunctional peptide composed of a silver binding peptide (AgBP) is covalently joined to an amelogenin derived peptide (ADP). The AgBP provides anchoring to the SDF-treated tooth tissue, while the ADP promotes rapid formation of a calcium phosphate isomorph nanocomposite mimicking the biomineralization function of the amelogenin protein. Our results demonstrate that the bifunctional peptide was effective in remineralizing the biomineral destroyed by caries on the SDF-treated tooth tissues. The proposed engineered peptide approach offers a biomimetic path for remineralization of the SDF-treated tissues producing a calcium phosphate nanocomposite interface competent to be restored using commonly available adhesive dental composites.

Recent advances in the design of antimicrobial peptide conjugates

Antimicrobial peptides (AMPs) are ubiquitous host defense peptides characterized by antibiotic activity and lower propensity for developing resistance compared to classic antibiotics. While several AMPs have shown activity against antibiotic-sensitive...

Antimicrobial peptide-based materials: opportunities and challenges

The multifunctional properties of antimicrobial peptides (AMPs) make them attractive candidates for the treatment of various diseases. AMPs are considered alternatives to antibiotics due to the rising number of multidrug-resistant...

Evaluation of a Hypersensitivity Inhibitor Containing a Novel Monomer That Induces Remineralization-A Case Series in Pediatric Patients

BACKGROUND

Recently, tooth deformities have been frequently encountered by pediatric dentists. Severe enamel hypomineralization sometimes induces pain such as hyperesthesia, but composite resin restoration is difficult because it often detaches without any cavity preparation. Resin-based hypersensitivity inhibitors for tooth physically seal the dentinal tubules. It was reported that hypersensitivity inhibitor containing novel adhesive monomers forms apatite and induces remineralization in vitro. Therefore, these case series assessed the clinical effects of remineralization and the suppression of hypersensitivity by Bio Coat Ca (Sun Medical, Shiga, Japan).

METHODS

After mechanical tooth cleaning was performed, the hypersensitivity inhibitors were applied and cured by light exposure. Changes in hypersensitivity were determined by visual analog scale (VAS). The improvement of hypomineralization was evaluated by the change in color tone based on the digital images of intraoral photographs.

RESULTS

After repeated monthly treatments, these cases showed decreased hypersensitivity after the fourth application, while the opaque white and brownish color improved on the seventh application.

CONCLUSION

This novel hypersensitivity inhibitor with calcium salt of 4-methacryloxyethyl trimellitic acid (C-MET) and 10-methacryloyloxydecyl dihydrogen calcium phosphate (MDCP) not only suppressed hypersensitivity but also improved cloudiness and brown spots in recently erupted permanent teeth in presented cases.

Application of Antimicrobial Peptides on Biomedical Implants: Three Ways to Pursue Peptide Coatings

Biofilm formation and inflammations are number one reasons of implant failure and cause a severe number of postoperative complications every year. To functionalize implant surfaces with antibiotic agents provides perspectives to minimize and/or prevent bacterial adhesion and proliferation. In recent years, antimicrobial peptides (AMP) have been evolved as promising alternatives to commonly used antibiotics, and have been seen as potent candidates for antimicrobial surface coatings. This review aims to summarize recent developments in this field and to highlight examples of the most common techniques used for preparing such AMP-based medical devices. We will report on three different ways to pursue peptide coatings, using either binding sequences (primary approach), linker layers (secondary approach), or loading in matrixes which offer a defined release (tertiary approach). All of them will be discussed in the light of current research in this area.

Martins MC, Costa F. Antimicrobial Peptides in the Battle against Orthopedic Implant-Related Infections: A Review

Prevention of orthopedic implant-related infections is a major medical challenge, particularly due to the involvement of biofilm-encased and multidrug-resistant bacteria. Current therapies, based on antibiotic administration, have proven to be insufficient, and infection prevalence may rise due to the dissemination of antibiotic resistance. Antimicrobial peptides (AMPs) have attracted attention as promising substitutes of conventional antibiotics, owing to their broad-spectrum of activity, high efficacy at very low concentrations, and, importantly, low propensity for inducing resistance. The aim of this review is to offer an updated perspective of the development of AMPs-based preventive strategies for orthopedic and dental implant-related infections. In this regard, two major research strategies are herein addressed, namely (i) AMP-releasing systems from titanium-modified surfaces and from bone cements or beads; and (ii) AMP immobilization strategies used to graft AMPs onto titanium or other model surfaces with potential translation as coatings. In overview, releasing strategies have evolved to guarantee higher loadings, prolonged and targeted delivery periods upon infection. In addition, avant-garde self-assembling strategies or polymer brushes allowed higher immobilized peptide surface densities, overcoming bioavailability issues. Future research efforts should focus on the regulatory demands for pre-clinical and clinical validation towards clinical translation.

Nanohybrids as Protein-Polymer Conjugate Multimodal Therapeutics

Protein therapeutic formulations are being widely explored as multifunctional nanotherapeutics. Challenges in ensuring susceptibility and efficacy of nanoformulation still prevail owing to various interactions with biological fluids before reaching the target site. Smart polymers with the capability of masking drugs, ease of chemical modification, and multi-stimuli responsiveness can assist controlled delivery. An active moiety like therapeutic protein has started to be known as an important biological formulation with a diverse medicinal prospect. The delivery of proteins and peptides with high target specificity has however been tedious, due to their tendency to aggregate formation in different environmental conditions. Proteins due to high chemical reactivity and poor bioavailability are being researched widely in the field of nanomedicine. Clinically, multiple nano-based formulations have been explored for delivering protein with different carrier systems. A biocompatible and non-toxic polymer-based delivery system serves to tailor the polymer or drug better. Polymers not only aid delivery to the target site but are also responsible for proper stearic orientation of proteins thus protecting them from internal hindrances. Polymers have been shown to conjugate with proteins through covalent linkage rendering stability and enhancing therapeutic efficacy prominently when dealing with the systemic route. Here, we present the recent developments in polymer-protein/drug-linked systems. We aim to address questions by assessing the properties of the conjugate system and optimized delivery approaches. Since thorough characterization is the key aspect for technology to enter into the market, correlating laboratory research with commercially available formulations will also be presented in this review. By examining characteristics including morphology, surface properties, and functionalization, we will expand different hybrid applications from a biomaterial stance applied in in vivo complex biological conditions. Further, we explore understanding related to design criteria and strategies for polymer-protein smart nanomedicines with their potential prophylactic theranostic applications. Overall, we intend to highlight protein-drug delivery through multifunctional smart polymers.

Novel Peptide-Polymer Conjugate with pH-Responsive Targeting/Disrupting Effects on Biomembranes

Conjugating polymers to peptides has become a new strategy of designing functional antitumor agents for their improved stability and enhanced activity. In this paper, a novel peptide-polymer conjugate PEPc-PMAA with pH responsiveness was designed and synthesized. The isoelectric point of PEPc was studied by dynamic light scattering for the targeting effect. Also, the transmittances of PMAA at different pHs were measured using an ultraviolet-visible spectrophotometer for determining the triggering pH of the disrupting effect. The results showed that PEPc-PMAA was hydrophilic under neutral conditions and changed to be amphiphilic composed of positively charged PEPc and hydrophobic PMAA under acidic conditions. The interactions between PEPc-PMAA and mimic cells were investigated by the measurements of membrane fluidity and cargo leakage from 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine and 1,2-dipalmitoyl-sn-glycerol-3-phospho-(1-rac-glycerol) (DPPG) liposomes. It proved that PEPc-PMAA caused a distinct membrane disturbance of the DPPG liposome at pH 5.5, resulting in more serious cargo leakage. Because of its targeting and disrupting effects on negatively charged biomembranes under acidic conditions, PEPc-PMAA showed its good potential as an antitumor agent.

Reconfigurable Dual Peptide Tethered Polymer System Offers a Synergistic Solution for Next Generation Dental Adhesives

Resin-based composite materials have been widely used in restorative dental materials due to their aesthetic, mechanical, and physical properties. However, they still encounter clinical shortcomings mainly due to recurrent decay that develops at the composite-tooth interface. The low-viscosity adhesive that bonds the composite to the tooth is intended to seal this interface, but the adhesive seal is inherently defective and readily damaged by acids, enzymes, and oral fluids. Bacteria infiltrate the resulting gaps at the composite-tooth interface and bacterial by-products demineralize the tooth and erode the adhesive. These activities lead to wider and deeper gaps that provide an ideal environment for bacteria to proliferate. This complex degradation process mediated by several biological and environmental factors damages the tooth, destroys the adhesive seal, and ultimately, leads to failure of the composite restoration. This paper describes a co-tethered dual peptide-polymer system to address composite-tooth interface vulnerability. The adhesive system incorporates an antimicrobial peptide to inhibit bacterial attack and a hydroxyapatite-binding peptide to promote remineralization of damaged tooth structure. A designer spacer sequence was incorporated into each peptide sequence to not only provide a conjugation site for methacrylate (MA) monomer but also to retain active peptide conformations and enhance the display of the peptides in the material. The resulting MA-antimicrobial peptides and MA-remineralization peptides were copolymerized into dental adhesives formulations. The results on the adhesive system composed of co-tethered peptides demonstrated both strong metabolic inhibition of S. mutans and localized calcium phosphate remineralization. Overall, the result offers a reconfigurable and tunable peptide-polymer hybrid system as next-generation adhesives to address composite-tooth interface vulnerability.

Recent Advances in the Development of Antimicrobial and Antifouling Biocompatible Materials for Dental Applications

The risk of secondary bacterial infections resulting from dental procedures has driven the design of antimicrobial and antifouling dental materials to curb pathogenic microbial growth, biofilm formation and subsequent oral and dental diseases. Studies have investigated approaches based primarily on contact-killing or release-killing materials. These materials are designed for addition into dental resins, adhesives and fillings or as immobilized coatings on tooth surfaces, titanium implants and dental prosthetics. This review discusses the recent developments in the different classes of biomaterials for antimicrobial and antifouling dental applications: polymeric drug-releasing materials, polymeric and metallic nanoparticles, polymeric biocides and antimicrobial peptides. With modifications to improve cytotoxicity and mechanical properties, contact-killing and anti-adhesion materials show potential for incorporation into dental materials for long-term clinical use as opposed to short-lived antimicrobial release-based coatings. However, extended durations of biocompatibility testing, and adjustment of essential biomaterial features to enhance material longevity in the oral cavity require further investigations to confirm suitability and safety of these materials in the clinical setting. The continuous exposure of dental restorative and regenerative materials to pathogenic microbes necessitates the implementation of antimicrobial and antifouling materials to either replace antibiotics or improve its rational use, especially in the day and age of the ever-increasing problem of antimicrobial resistance.

Combining genetic algorithm with machine learning strategies for designing potent antimicrobial peptides

BACKGROUND

Current methods in machine learning provide approaches for solving challenging, multiple constraint design problems. While deep learning and related neural networking methods have state-of-the-art performance, their vulnerability in decision making processes leading to irrational outcomes is a major concern for their implementation. With the rising antibiotic resistance, antimicrobial peptides (AMPs) have increasingly gained attention as novel therapeutic agents. This challenging design problem requires peptides which meet the multiple constraints of limiting drug-resistance in bacteria, preventing secondary infections from imbalanced microbial flora, and avoiding immune system suppression. AMPs offer a promising, bioinspired design space to targeting antimicrobial activity, but their versatility also requires the curated selection from a combinatorial sequence space. This space is too large for brute-force methods or currently known rational design approaches outside of machine learning. While there has been progress in using the design space to more effectively target AMP activity, a widely applicable approach has been elusive. The lack of transparency in machine learning has limited the advancement of scientific knowledge of how AMPs are related among each other, and the lack of general applicability for fully rational approaches has limited a broader understanding of the design space.

METHODS

Here we combined an evolutionary method with rough set theory, a transparent machine learning approach, for designing antimicrobial peptides (AMPs). Our method achieves the customization of AMPs using supervised learning boundaries. Our system employs in vitro bacterial assays to measure fitness, codon-representation of peptides to gain flexibility of sequence selection in DNA-space with a genetic algorithm and machine learning to further accelerate the process.

RESULTS

We use supervised machine learning and a genetic algorithm to find a peptide active against S. epidermidis, a common bacterial strain for implant infections, with an improved aggregation propensity average for an improved ease of synthesis.

CONCLUSIONS

Our results demonstrate that AMP design can be customized to maintain activity and simplify production. To our knowledge, this is the first time when codon-based genetic algorithms combined with rough set theory methods is used for computational search on peptide sequences.

Chemometrics-Assisted Raman Spectroscopy Characterization of Tunable Polymer-Peptide Hybrids for Dental Tissue Repair

The interfaces that biological tissues form with biomaterials are invariably defective and frequently the location where failure initiates. Characterizing the phenomena that lead to failure is confounded by several factors including heterogeneous material/tissue interfaces. To seamlessly analyze across these diverse structures presents a wealth of analytical challenges. This study aims to develop a molecular-level understanding of a peptide-functionalized adhesive/collagen hybrid biomaterial using Raman spectroscopy combined with chemometrics approach. An engineered hydroxyapatite-binding peptide (HABP) was copolymerized in dentin adhesive and dentin was demineralized to provide collagen matrices that were partially infiltrated with the peptide-functionalized adhesive. Partial infiltration led to pockets of exposed collagen-a condition that simulates defects in adhesive/dentin interfaces. The spectroscopic results indicate that co-polymerizable HABP tethered to the adhesive promoted remineralization of the defects. The spatial distribution of collagen, adhesive, and mineral as well as crystallinity of the mineral across this heterogeneous material/tissue interface was determined using micro-Raman spectroscopy combined with chemometrics approach. The success of this combined approach in the characterization of material/tissue interfaces stems from its ability to extract quality parameters that are related to the essential and relevant portions of the spectral data, after filtering out noise and non-relevant information. This ability is critical when it is not possible to separate components for analysis such as investigations focused on, in situ chemical characterization of interfaces. Extracting essential information from complex bio/material interfaces using data driven approaches will improve our understanding of heterogeneous material/tissue interfaces. This understanding will allow us to identify key parameters within the interfacial micro-environment that should be harnessed to develop durable biomaterials.

Probing the mineralized tissue-adhesive interface for tensile nature and bond strength

The mechanical performance of the dentin-adhesive interface contributes significantly to the failure of dental composite restorations. Rational material design can lead to enhanced mechanical performance, but this requires accurate characterization of the mechanical behavior at the dentin-adhesive interface. The mechanical performance of the interface is typically characterized using bond strength tests, such as the micro-tensile test. These tests are plagued by multiple limitations including large variations in the test results. The challenges associated with conventional tensile tests limit our ability to unravel the complex relationships that affect mechanical behavior at the dentin-adhesive interface. This study used the diametral compression test to overcome the challenges inherent in conventional bond strength tests. The bovine femur cortical bone tissue was considered as a surrogate material (the mineralized tissue) for human dentin. Two different adhesive formulations, which differed by means of their self-strengthening properties, were studied. The tensile behavior of the mineralized tissue, the adhesive polymer, and the bond strength of the mineralized tissue - adhesive interface was determined using the diametral compression test. The diametral compression test improved the repeatability for both the tensile and bond strength tests. The rate dependent mechanical behavior was observed for both single material and interfacial material systems. The tensile strength and bond strength of the mineralized tissue-adhesive interface was greater for the self-strengthening formulation as compared to the control.

Advances of peptides for antibacterial applications

In the past few decades, peptide antibacterial products with unique antibacterial mechanisms have attracted widespread interest. They can effectively reduce the probability of drug resistance of bacteria and are biocompatible, so they possess tremendous development prospects. This review provides recent research and analysis on the basic types of antimicrobial peptides (including poly (amino acid)s, short AMPs, and lipopeptides) and factors to optimize antimicrobial effects. It also summarizes the two most important modes of action of antimicrobial peptides and the latest developments in the application of AMPs, including antimicrobial agent, wound healing, preservative, antibacterial coating and others. Finally, we discuss the remaining challenges to improve the antibacterial peptides and propose prospects in the field.

Antibiofilm coatings based on protein-engineered polymers and antimicrobial peptides for preventing implant-associated infections

Implant-associated infections (IAIs) are one of the leading concerns in orthopedics and dentistry as they commonly lead to implant failure. The presence of biofilms and, increasingly frequently, drug-resistant bacteria further impairs the efficacy of conventional antibiotics. Immobilization of antimicrobial peptides (AMPs) on implant surfaces is a promising alternative to antibiotics for prevention of IAIs. In addition, the use of functional linkers for the AMP tethering enables to increase the antimicrobial potential and the bioactivities of the coating. In this study, an extracellular-matrix-mimicking system based on elastin-like recombinamers (ELRs) has been developed for the covalent anchoring of AMPs and investigated for use as a hybrid antibiofilm coating. A drip-flow biofilm reactor was used to simulate in vivo environmental dynamic conditions, thus showing that the presence of the AMPs in the hybrid coatings provided strong antibiofilm activity against monospecies and microcosm biofilm models of clinical relevance. These results, together with an excellent cytocompatibility towards primary gingival fibroblasts, encourage the use of ELRs as multivalent platforms for AMPs and open up a wide range of possibilities in the biofabrication of advanced coatings combining the antibiofilm potential of AMPs and the outstanding tunability and biomechanical properties of the ELRs.

Unraveling dominant surface physicochemistry to build antimicrobial peptide coatings with supramolecular amphiphiles

With the increasing threat from antibiotic-resistant bacteria, surface modification with antimicrobial peptides (AMP) has been promisingly explored for preventing bacterial infections. Little is known about the critical factors that govern AMP-surface interactions to obtain stable and active coatings. Here, we systematically monitored the adsorption of a designer amphipathic AMP, GL13K, on model surfaces. Self-assembly of the GL13K peptides formed supramolecular amphiphiles that highly adsorbed on negatively charged, polar hydroxyapatite-coated sensors. We further tuned surface charge and/or surface polarity with self-assembled monolayers (SAMs) on Au sensors and studied their interactions with adsorbed GL13K. We determined that the surface polarity of the SAM-coated sensors instead of their surface charge was the dominant factor governing AMP/substrate interactions via hydrogen bonding. Our findings will instruct the universal design of efficient self-assembled AMP coatings on biomaterials, biomedical devices and/or natural tissues.

Strategies for antimicrobial peptide coatings on medical devices: a review and regulatory science perspective

Indwelling and implanted medical devices are subject to contamination by microbial pathogens during surgery, insertion or injection, and ongoing use, often resulting in severe nosocomial infections. Antimicrobial peptides (AMPs) offer a promising alternative to conventional antibiotics to reduce the incidence of such infections, as they exhibit broad-spectrum antimicrobial activity against Gram-negative and Gram-positive bacteria, microbial biofilms, fungi, and viruses. In this review-perspective, we first provide an overview of the progress made in this field over the past decade with an emphasis on the local release of AMPs from implant surfaces and immobilization strategies for incorporating these agents into a wide range of medical device materials. We then provide a regulatory science perspective addressing the characterization and testing of AMP coatings based on the type of immobilization strategy used with a focus on the US market regulatory niche. Our goal is to help narrow the gulf between academic studies and preclinical testing, as well as to support a future literature base in order to develop the regulatory science of antimicrobial coatings.

Harnessing biomolecules for bioinspired dental biomaterials

Dental clinicians have relied for centuries on traditional dental materials (polymers, ceramics, metals, and composites) to restore oral health and function to patients. Clinical outcomes for many crucial dental therapies remain poor despite many decades of intense research on these materials. Recent attention has been paid to biomolecules as a chassis for engineered preventive, restorative, and regenerative approaches in dentistry. Indeed, biomolecules represent a uniquely versatile and precise tool to enable the design and development of bioinspired multifunctional dental materials to spur advancements in dentistry. In this review, we survey the range of biomolecules that have been used across dental biomaterials. Our particular focus is on the key biological activity imparted by each biomolecule toward prevention of dental and oral diseases as well as restoration of oral health. Additional emphasis is placed on the structure-function relationships between biomolecules and their biological activity, the unique challenges of each clinical condition, limitations of conventional therapies, and the advantages of each class of biomolecule for said challenge. Biomaterials for bone regeneration are not reviewed as numerous existing reviews on the topic have been recently published. We conclude our narrative review with an outlook on the future of biomolecules in dental biomaterials and potential avenues of innovation for biomaterial-based patient oral care.

Antibacterial Activity and Potential Application in Food Packaging of Peptides Derived from Turbot Viscera Hydrolysate

As a good choice for food preservation, antimicrobial peptides (AMPs) have received much attention in recent years. In this paper, peptides derived from the turbot viscera hydrolysate were identified by ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS), and the physicochemical properties and structural characteristics were analyzed by in silico tools. Furthermore, three cationic peptides with potential hydrophobicity and amphipathy were synthesized; their cytotoxicity, hemolysis, and antibacterial activities were investigated. In particular, Sm-A1 (GITDLRGMLKRLKKMK), a peptide with 16 amino acids, showed an outstanding antibacterial activity against both Gram-positive and Gram-negative bacteria by damaging the cell membrane integrity. Moreover, Sm-A1 was successfully loaded into hydroxyl-rich poly(vinyl alcohol) (PVA)/chitosan (CS) hydrogel to improve the antibacterial activity and biofilm inhibition effect. PVA/CS+7.5‰ Sm-A1 hydrogel can satisfactorily protect the salmon muscle from the microbiological contamination and texture deterioration.

Cationic Amphiphilic Peptides: Synthetic Antimicrobial Agents Inspired by Nature

Antimicrobial peptides are ubiquitous in multicellular organisms and have served as defense mechanisms for their successful evolution and throughout their life cycle. These peptides are short cationic amphiphilic polypeptides of fewer than 50 amino acids containing either a few disulfide-linked cysteine residues with a characteristic β-sheet-rich structure or linear α-helical conformations with hydrophilic side chains at one side of the helix and hydrophobic side chains on the other side. Antimicrobial peptides cause bacterial cell lysis either by direct cell-surface damage via electrostatic interactions between the cationic side chains of the peptide and the negatively charged cell surface, or by indirect modulation of the host defense systems. Electrostatic interactions lead to bacterial cell membrane disruption followed by leakage of cellular components and finally bacterial cell death. Because of their unusual mechanism of cell damage, antimicrobial peptides are effective against drug-resistant bacteria and may therefore prove more effective than classical antibiotics in certain cases. Currently, around 3000 natural antimicrobial peptides from six kingdoms (bacteria, archaea, protists, fungi, plants, and animals) have been isolated and sequenced. However, only a few of them are under clinical trials and/or in the commercial development stage for the treatment of bacterial infections caused by antibiotic-resistant bacteria. Moreover, high structural complexity, poor pharmacokinetic properties, and low antibacterial activity of natural antimicrobial peptides hinder their progress in drug development. To overcome these hurdles, researchers have become increasingly interested in modification and nature-inspired synthetic antimicrobial peptides. This review discusses some of the recent studies reported on antimicrobial peptides.

Antibacterial properties of Magainin II peptide onto 304 stainless steel surfaces: A comparison study of two dopamine modification methods

Marine biofouling is perplexing the development of marine industry, and the traditional antifouling methods are restricted by the requirements of marine environmental friendliness. Marine bacteria attachment is the initial stage of marine fouling and it can be effectively reduced by reducing bacterial attachment. In this study, two modification methods were reported to synthesize antibacterial surfaces based on the different order of Magainin Ⅱ (MAG Ⅱ) modification. The preparation of SS-DA-M was generated by modifying the 304 stainless steel (304 SS) surface with dopamine firstly and then grafting the MAG Ⅱ onto the dopamine modified surface; SS-M-DA was obtained by modifying 304 SS surface using MAG Ⅱ derivative which synthesized by MAG Ⅱ and dopamine under weak acid condition. XPS, contact angle, film thickness and surface topography analysis showed that both methods grafted MAG Ⅱ onto the 304 SS surface successfully, changing the morphology and wettability of the substrates. Antibacterial results demonstrated that the two modified surfaces possessed strong resistance against V. natriegens, and the antibacterial efficiency of SS-DA-M and SS-M-DA reached 98.07 % and 99.79 %, respectively. Robustness results illustrated that the modified surface could keep strong antibacterial capacity in seawater for a long time. The phy-chemical properties and antibacterial properties of SS-M-DA surface were superior to SS-DA-M surface because more MAG Ⅱ were grafted onto 304 SS surface and the distribution was more uniform than the SS-DA-M surface. The investigation may offer a new and promising strategy to tackle surface fouling of hull, aquaculture cage and other marine facilities.