Polymer coated liposomes for dental drug delivery – Interactions with parotid saliva and dental enamel

Polymer vesicles for the delivery of inhibitors of cariogenic biofilm

OBJECTIVES

The goal of this study is to develop a novel drug delivery platform for the pH-responsive delivery of biofilm inhibitors as a potential avenue to prevent and treat dental caries.

METHODS

Biofilm and growth inhibition assays were performed in polystyrene microtiter 96-well plates. Docking analysis was performed using the reported GtfB + HA5 co-crystal structure (PDB code: 8fg8) in SeeSAR 13.0.1 software. Polymersome vesicles were assembled from poly(N-vinylpyrrolidone)8-block-poly(dimethylsiloxane)64-block-poly(N-vinylpyrrolidone)8 (PVPON8-PDMS64-PVPON8) triblock copolymer using a nanoprecipitation method. Microbiome analysis of biofilm inhibitors and the in vivo drug release and antivirulence activities of polymersome encapsulated inhibitors have been carried out in a S. mutans induced rat caries model.

RESULTS

Biofilm inhibitors for HA5 and HA6 have shown species-specific selectivity towards S. mutans and the ability to preserve the oral microbiome in a S. mutans induced dental caries model. The inhibitors were encapsulated into pH-responsive block copolymer vesicles to generate polymersome-encapsulated biofilm inhibitors, and their biofilm and growth inhibitory activities against S. mutans and representative strains of oral commensal streptococci have been assessed. A 4-week treatment of S. mutans UA159 infected gnotobiotic rats with 100 µM of polymersome-encapsulated biofilm inhibitor, PEHA5 showed significant reductions in buccal, sulcal, and proximal caries scores compared to an untreated control group.

SIGNIFICANCE

Taken together, our data suggests that the biofilm-selective therapy using the polymersome-encapsulated biofilm inhibitors is a viable approach for the prevention and treatment of dental caries while preserving the oral microbiome.

Hydrogel-Encapsulated Biofilm Inhibitors Abrogate the Cariogenic Activity of Streptococcus mutans

We designed and synthesized analogues of a previously identified biofilm inhibitor IIIC5 to improve solubility, retain inhibitory activities, and to facilitate encapsulation into pH-responsive hydrogel microparticles. The optimized lead compound HA5 showed improved solubility of 120.09 μg/mL, inhibited Streptococcus mutans biofilm with an IC50 value of 6.42 μM, and did not affect the growth of oral commensal species up to a 15-fold higher concentration. The cocrystal structure of HA5 with GtfB catalytic domain determined at 2.35 Å resolution revealed its active site interactions. The ability of HA5 to inhibit S. mutans Gtfs and to reduce glucan production has been demonstrated. The hydrogel-encapsulated biofilm inhibitor (HEBI), generated by encapsulating HA5 in hydrogel, selectively inhibited S. mutans biofilms like HA5. Treatment of S. mutans-infected rats with HA5 or HEBI resulted in a significant reduction in buccal, sulcal, and proximal dental caries compared to untreated, infected rats.

Nanomaterials in Dentistry: Current Applications and Future Scope

Nanotechnology utilizes the mechanics to control the size and morphology of the particles in the required nano range for accomplishing the intended purposes. There was a time when it was predominantly applied only to the fields of matter physics or chemical engineering, but with time, biological scientists recognized its vast benefits and explored the advantages in their respective fields. This extension of nanotechnology in the field of dentistry is termed ‘Nanodentistry.’ It is revolutionizing every aspect of dentistry. It consists of therapeutic and diagnostic tools and supportive aids to maintain oral hygiene with the help of nanomaterials. Research in nanodentistry is evolving holistically but slowly with the advanced finding of symbiotic use of novel polymers, natural polymers, metals, minerals, and drugs. These materials, in association with nanotechnology, further assist in exploring the usage of nano dental adducts in prosthodontic, regeneration, orthodontic, etc. Moreover, drug release cargo abilities of the nano dental adduct provide an extra edge to dentistry over their conventional counterparts. Nano dentistry has expanded to every single branch of dentistry. In the present review, we will present a holistic view of the recent advances in the field of nanodentistry. The later part of the review compiled the ethical and regulatory challenges in the commercialization of the nanodentistry. This review tracks the advancement in nano dentistry in different but important domains of dentistry.

Stress impact of liposomes loaded with ciprofloxacin on the expression level of MepA and NorB efflux pumps of methicillin-resistant Staphylococcus aureus

One mechanism of ciprofloxacin resistance is attributed to chromosomal DNA-encoded efflux pumps such as the MepA and NorB proteins. The goal of this research is to find a way to bypass Staphylococcus aureus' efflux pumps. Because of its high membrane permeability and low association with NorB and MepA efflux proteins, a liposome-encapsulating antibiotic is one of the promising, cost-effective drug carriers and coating mechanisms for overcoming active transport of methicillin-resistant S. aureus (MRSA) multidrug-resistant efflux protein . The calculated "Log Perm RRCK" membrane permeability values of 1,2-distearoyl-sn-glycerol-3-phosphocholine (DSPC) ciprofloxacin liposome-encapsulated (CFL) showed a lower negative value of - 4,652 cm/s and greater membrane permeability than ciprofloxacin free (CPF). The results of RT-qPCR showed that cationic liposomes containing ciprofloxacin in liposome-encapsulated form (CFL) improved CPF antibacterial activity and affinity for negatively charged bacterial cell surface membrane in comparison to free drug and liposome, as it overcame several resistance mechanisms and reduced the expression of efflux pumps. Ciprofloxacin liposome-encapsulated (CFL) is therefore more effective than ciprofloxacin alone. Liposomes can be combined with a variety of drugs that interact with bacterial cell efflux pumps to maintain high sustained levels of antibiotics in bacterial cells.

Polysaccharide-Based Micro- and Nanosized Drug Delivery Systems for Potential Application in the Pediatric Dentistry

The intensive development of micro- and nanotechnologies in recent years has offered a wide horizon of new possibilities for drug delivery in dentistry. The use of polymeric drug carriers turned out to be a very successful technique for formulating micro- and nanoparticles with controlled or targeted drug release in the oral cavity. Such innovative strategies have the potential to provide an improved therapeutic approach to prevention and treatment of various oral diseases not only for adults, but also in the pediatric dental practice. Due to their biocompatibility, biotolerance and biodegradability, naturally occurring polysaccharides like chitosan, alginate, pectin, dextran, starch, etc., are among the most preferred materials for preparation of micro- and nano-devices for drug delivery, offering simple particle-forming characteristics and easily tunable properties of the formulated structures. Their low immunogenicity and low toxicity provide an advantage over most synthetic polymers for the development of pediatric formulations. This review is focused on micro- and nanoscale polysaccharide biomaterials as dental drug carriers, with an emphasis on their potential application in pediatric dentistry.

Natural Polymers for the Maintenance of Oral Health: Review of Recent Advances and Perspectives

The success of modern dental treatment is strongly dependent on the materials used both temporarily and permanently. Among all dental materials, polymers are a very important class with a wide spectrum of applications. This review aims to provide a state-of-the-art overview of the recent advances in the field of natural polymers used to maintain or restore oral health. It focuses on the properties of the most common proteins and polysaccharides of natural origin in terms of meeting the specific biological requirements in the increasingly demanding field of modern dentistry. The use of naturally derived polymers in different dental specialties for preventive and therapeutic purposes has been discussed. The major fields of application cover caries and the management of periodontal diseases, the fabrication of membranes and scaffolds for the regeneration of dental structures, the manufacturing of oral appliances and dentures as well as providing systems for oral drug delivery. This paper also includes a comparative characteristic of natural and synthetic dental polymers. Finally, the current review highlights new perspectives, possible future advancements, as well as challenges that may be encountered by researchers in the field of dental applications of polymers of natural origin.

Polymer-Based Carriers in Dental Local Healing-Review and Future Challenges

Polymers in drug formulation technology and the engineering of biomaterials for the treatment of oral diseases constitute a group of excipients that often possess additional properties in addition to their primary function, i.e., biological activity, sensitivity to stimuli, mucoadhesive properties, improved penetration of the active pharmaceutical ingredient (API) across biological barriers, and effects on wound healing or gingival and bone tissue regeneration. Through the use of multifunctional polymers, it has become possible to design carriers and materials tailored to the specific conditions and site of application, to deliver the active substance directly to the affected tissue, including intra-periodontal pocket delivery, and to release the active substance in a timed manner, allowing for the improvement of the form of application and further development of therapeutic strategies. The scope of this review is polymeric drug carriers and materials developed from selected multifunctional groups of natural, semi-synthetic, and synthetic polymers for topical therapeutic applications. Moreover, the characteristics of the topical application and the needs for the properties of carriers for topical administration of an active substance in the treatment of oral diseases are presented to more understand the difficulties associated with the design of optimal active substance carriers and materials for the treatment of lesions located in the oral cavity.

Liposome as a delivery system for the treatment of biofilm-mediated infections

Biofilm formation by pathogenic microorganisms has been a tremendous challenge for antimicrobial therapies due to various factors. The biofilm matrix sequesters bacterial cells from the exterior environment and therefore prevents antimicrobial agents from reaching the interior. In addition, biofilm surface extracellular polymeric substances can absorb antimicrobial agents and thus reduce their bioavailability. To conquer these protection mechanisms, liposomes have been developed into a drug delivery system for antimicrobial agents against biofilm-mediated infections. The unique characteristics of liposomes, including versatility for cargoes, target-specificity, nonimmunogenicity, low toxicity, and biofilm matrix-/cell membrane-fusogenicity, remarkably improve the effectiveness of antimicrobial agents and minimize recurrence of infections. This review summarizes current development of liposomal carriers for biofilm therapeutics, presents evidence in their practical applications and discusses their potential limitations.

Nanotechnology-Based Antimicrobial and Antiviral Surface Coating Strategies

Biocontamination of medical devices and implants is a growing issue that causes medical complications and increased expenses. In the fight against biocontamination, developing synthetic surfaces, which reduce the adhesion of microbes and provide biocidal activity or combinatory effects, has emerged as a major global strategy. Advances in nanotechnology and biological sciences have made it possible to design smart surfaces for decreasing infections. Nevertheless, the clinical performance of these surfaces is highly depending on the choice of material. This review focuses on the antimicrobial surfaces with functional material coatings, such as cationic polymers, metal coatings and antifouling micro-/nanostructures. One of the highlights of the review is providing insights into the virus-inactivating surface development, which might particularly be useful for controlling the currently confronted pandemic coronavirus disease 2019 (COVID-19). The nanotechnology-based strategies presented here might be beneficial to produce materials that reduce or prevent the transmission of airborne viral droplets, once applied to biomedical devices and protective equipment of medical workers. Overall, this review compiles existing studies in this broad field by focusing on the recent related developments, draws attention to the possible activity mechanisms, discusses the key challenges and provides future recommendations for developing new, efficient antimicrobial and antiviral surface coatings.

Advances of Anti-Caries Nanomaterials

Caries is the most common and extensive oral chronic disease. Due to the lack of anti-caries properties, traditional caries filling materials can easily cause secondary caries and lead to treatment failure. Nanomaterials can interfere with the bacteria metabolism, inhibit the formation of biofilm, reduce demineralization, and promote remineralization, which is expected to be an effective strategy for caries management. The nanotechnology in anti-caries materials, especially nano-adhesive and nano-composite resin, has developed fast in recent years. In this review, the antibacterial nanomaterials, remineralization nanomaterials, and nano-drug delivery systems are reviewed. We are aimed to provide a theoretical basis for the future development of anti-caries nanomaterials.

A Review of Biodegradable Natural Polymer-Based Nanoparticles for Drug Delivery Applications

Biodegradable natural polymers have been investigated extensively as the best choice for encapsulation and delivery of drugs. The research has attracted remarkable attention in the pharmaceutical industry. The shortcomings of conventional dosage systems, along with modified and targeted drug delivery methods, are addressed by using polymers with improved bioavailability, biocompatibility, and lower toxicity. Therefore, nanomedicines are now considered to be an innovative type of medication. This review critically examines the use of natural biodegradable polymers and their drug delivery systems for local or targeted and controlled/sustained drug release against fatal diseases.

Flash tooth whitening: A friendly formulation based on a nanoencapsulated reductant

Tooth whitening materials have not undergone relevant advances in the last years. Current materials base their action on the oxidant activity of peroxides, which present the disadvantage of requiring long application times, along with unpleasant side effects of dental hypersensitivity (e.g. sharp pain). In this work, a novel tooth whitening formulation based on the encapsulation of a reducing agent (sodium metabisulfite) in liposomes is developed. An experimental design was applied to optimize the formulation in terms of whitening action and safety, using bovine teeth as in vitro model. Results were obtained by colorimetry, profilometry and nanoindentation techniques. The comparison with standard whitening treatments showed a similar whitening action of the optimized formulation but in remarkable shorter application times. Moreover, teeth roughness values obtained with the presented formulation conformed with ISO 28399. As mechanism of action, results obtained from fluorescent confocal microscopy showed the liposomal formulation to form a layer surrounding the enamel surface, enhancing the treatment efficacy in terms of diffusion of the protected reductant towards the enamel. The better efficiency of this formulation encourages its use as an alternative to current oxidative treatments.

Nanocapsule pH Regulator: Sustained Continuous Alkali Release from Thermosensitive Liposomes Reduces Acid Erosion

Thermosensitive liposomes are major drug delivery carriers, which enable targeting of drugs and burst release of the drugs from the liposomes at the site of action by applying a local heat stimulation above body temperature. Although the burst release is significant for a one-shot high-rate release of drugs at the target site, this type of release has a limited sustained action of the drugs. In this study, we report the alkali-encapsulating thermosensitive liposomes enabling environment pH regulation by sustained continuous cargo release at human body temperature. The liposomes encapsulating alkalis successfully neutralized the environmental acids for hours by releasing the alkalis and prevented acid erosion of hydroxyapatite matrix. Taken together, the present liposomes are effective for the sustained release of cargo at body temperature, specifically the alkali-encapsulating liposomes can be a preventing agent for dental caries in the oral cavity. The sustained release under endogenous body heat characteristics of thermosensitive liposomes showcased in this study can also be extended for prolonged intravenous drug exposure from targeted liposomal drug nanotherapeutics in the near future.

Lipid-Based Antimicrobial Delivery-Systems for the Treatment of Bacterial Infections

Many nanotechnology-based antimicrobials and antimicrobial-delivery-systems have been developed over the past decades with the aim to provide alternatives to antibiotic treatment of infectious-biofilms across the human body. Antimicrobials can be loaded into nanocarriers to protect them against de-activation, and to reduce their toxicity and potential, harmful side-effects. Moreover, antimicrobial nanocarriers such as micelles, can be equipped with stealth and pH-responsive features that allow self-targeting and accumulation in infectious-biofilms at high concentrations. Micellar and liposomal nanocarriers differ in hydrophilicity of their outer-surface and inner-core. Micelles are self-assembled, spherical core-shell structures composed of single layers of surfactants, with hydrophilic head-groups and hydrophobic tail-groups pointing to the micellar core. Liposomes are composed of lipids, self-assembled into bilayers. The hydrophilic head of the lipids determines the surface properties of liposomes, while the hydrophobic tail, internal to the bilayer, determines the fluidity of liposomal-membranes. Therefore, whereas micelles can only be loaded with hydrophobic antimicrobials, hydrophilic antimicrobials can be encapsulated in the hydrophilic, aqueous core of liposomes and hydrophobic or amphiphilic antimicrobials can be inserted in the phospholipid bilayer. Nanotechnology-derived liposomes can be prepared with diameters <100-200 nm, required to prevent reticulo-endothelial rejection and allow penetration into infectious-biofilms. However, surface-functionalization of liposomes is considerably more difficult than of micelles, which explains while self-targeting, pH-responsive liposomes that find their way through the blood circulation toward infectious-biofilms are still challenging to prepare. Equally, development of liposomes that penetrate over the entire thickness of biofilms to provide deep killing of biofilm inhabitants still provides a challenge. The liposomal phospholipid bilayer easily fuses with bacterial cell membranes to release high antimicrobial-doses directly inside bacteria. Arguably, protection against de-activation of antibiotics in liposomal nanocarriers and their fusogenicity constitute the biggest advantage of liposomal antimicrobial carriers over antimicrobials free in solution. Many Gram-negative and Gram-positive bacterial strains, resistant to specific antibiotics, have been demonstrated to be susceptible to these antibiotics when encapsulated in liposomal nanocarriers. Recently, also progress has been made concerning large-scale production and long-term storage of liposomes. Therewith, the remaining challenges to develop self-targeting liposomes that penetrate, accumulate and kill deeply in infectious-biofilms remain worthwhile to pursue.

Lipid-Based Antimicrobial Delivery-Systems for the Treatment of Bacterial Infections

Many nanotechnology-based antimicrobials and antimicrobial-delivery-systems have been developed over the past decades with the aim to provide alternatives to antibiotic treatment of infectious-biofilms across the human body. Antimicrobials can be loaded into nanocarriers to protect them against de-activation, and to reduce their toxicity and potential, harmful side-effects. Moreover, antimicrobial nanocarriers such as micelles, can be equipped with stealth and pH-responsive features that allow self-targeting and accumulation in infectious-biofilms at high concentrations. Micellar and liposomal nanocarriers differ in hydrophilicity of their outer-surface and inner-core. Micelles are self-assembled, spherical core-shell structures composed of single layers of surfactants, with hydrophilic head-groups and hydrophobic tail-groups pointing to the micellar core. Liposomes are composed of lipids, self-assembled into bilayers. The hydrophilic head of the lipids determines the surface properties of liposomes, while the hydrophobic tail, internal to the bilayer, determines the fluidity of liposomal-membranes. Therefore, whereas micelles can only be loaded with hydrophobic antimicrobials, hydrophilic antimicrobials can be encapsulated in the hydrophilic, aqueous core of liposomes and hydrophobic or amphiphilic antimicrobials can be inserted in the phospholipid bilayer. Nanotechnology-derived liposomes can be prepared with diameters <100-200 nm, required to prevent reticulo-endothelial rejection and allow penetration into infectious-biofilms. However, surface-functionalization of liposomes is considerably more difficult than of micelles, which explains while self-targeting, pH-responsive liposomes that find their way through the blood circulation toward infectious-biofilms are still challenging to prepare. Equally, development of liposomes that penetrate over the entire thickness of biofilms to provide deep killing of biofilm inhabitants still provides a challenge. The liposomal phospholipid bilayer easily fuses with bacterial cell membranes to release high antimicrobial-doses directly inside bacteria. Arguably, protection against de-activation of antibiotics in liposomal nanocarriers and their fusogenicity constitute the biggest advantage of liposomal antimicrobial carriers over antimicrobials free in solution. Many Gram-negative and Gram-positive bacterial strains, resistant to specific antibiotics, have been demonstrated to be susceptible to these antibiotics when encapsulated in liposomal nanocarriers. Recently, also progress has been made concerning large-scale production and long-term storage of liposomes. Therewith, the remaining challenges to develop self-targeting liposomes that penetrate, accumulate and kill deeply in infectious-biofilms remain worthwhile to pursue.

Polymeric materials and films in dentistry: An overview

The use of polymeric materials (PMs) and polymeric films (PMFs) has increased in medicine and dentistry. This increasing interest is attributed to not only the excellent surfaces of PMs and PMFs but also their desired mechanical and biological properties, low production cost, and ease in processing, allowing them to be tailored for a wide range of applications. Specifically, PMs and PMFs are used in dentistry for their antimicrobial, drug delivery properties; in preventive, restorative and regenerative therapies; and for corrosion and friction reduction. PMFs such as acrylic acid copolymers are used as a dental adhesive; polylactic acids are used for dental pulp and dentin regeneration, and bioactive polymers are used as advanced drug delivery systems. The objective of this article was to review the literatures on the latest advancements in the use of PMs and PMFs in medicine and dentistry. Published literature (1990–2017) on PMs and PMFs for use in medicine and dentistry was reviewed using MEDLINE/PubMed and ScienceDirect resources. Furthermore, this review also explores the diversity of latest PMs and PMFs that have been utilized in dental applications, and analyzes the benefits and limitations of PMs and PMFs. Most of the PMs and PMFs have shown to improve the biomechanical properties of dental materials, but in future, more clinical studies are needed to create better treatment guidelines for patients.

[Research progress on a nanodrug delivery system for prevention and control of dental caries and periodontal diseases]

Dental caries and periodontal diseases are common chronic infectious diseases that cause serious damage to oral health. Bacteria is the primary factor leading to such conditions. As a dental plaque control method, chemotherapeutic agents face serious challenges in dental care because of the specific physiological and anatomical characteristics of the oral cavity. Nanodrug delivery system is a series of new drug delivery systems at nanoscale, and it can target cells, promote sustainedrelease effects, and enhance biodegradation. This review focuses on research progress on nanodrug delivery systems for prevention and control of dental caries and periodontal diseases.

Advanced drug delivery systems for local treatment of the oral cavity

Good oral health is of major importance for general health and well-being. Several innovative drug delivery systems have been developed for the local treatment and prevention of various diseases in the oral cavity. However, there are currently few optimal systems and many therapeutic challenges still remain, including low drug efficacy and retention at targeted site of action. The present review provides an insight into the latest drug delivery strategies for the local treatment and prevention of the four most common oral pathologies, namely, dental caries, periodontitis, oral mucosal infections and oral cancer. The potential of bioadhesive formulations, nanoparticulate platforms, multifunctional systems and photodynamic methodologies to improve therapy and prophylaxis in future local applications for the oral cavity will be discussed.

Recent advances in liposome surface modification for oral drug delivery

Oral delivery via the gastrointestinal (GI) tract is the dominant route for drug administration. Orally delivered liposomal carriers can enhance drug solubility and protect the encapsulated theraputic agents from the extreme conditions found in the GI tract. Liposomes, with their fluid lipid bilayer membrane and their nanoscale size, can significantly improve oral absorption. Unfortunately, the clinical applications of conventional liposomes have been hindered due to their poor stability and availability under the harsh conditions typically presented in the GI tract. To overcome this problem, the surface modification of liposomes has been investigated. Although liposome surface modification has been extensively studied for oral drug delivery, no review exists so far that adequately covers this topic. The purpose of this paper is to summarize and critically analyze emerging trends in liposome surface modification for oral drug delivery.

Interactions of liposomes with dental restorative materials

The in vitro adsorption and retention of liposomes onto four common types of dental restorative materials (conventional and silorane-based resin composites as well as conventional and resin-modified glass ionomer cements (GIC)) have been investigated due to their potential use in the oral cavity. Uncoated liposomes (positively and negatively charged) and pectin (low- and high-methoxylated) coated liposomes were prepared and characterized in terms of particle size and zeta potential. The adsorption of liposomes was performed by immersion, quantified by fluorescence detection, and visualized by fluorescence imaging and atomic force microscopy. Positive liposomes demonstrated the highest adsorption on all four types of materials likely due to their attractive surface charge. They also retained well (minimum 40% after 60 min) on both conventional resin composite and GIC even when exposed to simulated salivary flow. Although an intermediate initial level of adsorption was found for the pectin coated liposomes, at least 70% high methoxylated-pectin coated liposomes still remained on the conventional resin composite after 60 min flow exposure. This indicates significant contribution of hydrophobic interactions in the prolonged binding of liposomes to resin composites. Based on these results, the present paper suggests two new possible applications of liposomes in the preservation of dental restorations.