Dextrin/poly (HEMA): pH responsive porous hydrogel for controlled release of ciprofloxacin

Synthesis and Evaluation of Antifungal and Antibacterial Abilities of Carbon Nanotubes Grafted to Poly(2-hydroxyethyl methacrylate) Nanocomposites

Developing nanomaterials with the capacity to restrict the growth of bacteria and fungus is of current interest. In this study, nanocomposites of poly(2-hydroxyethyl methacrylate) (PHEMA) and carbon nanotubes (CNTs) functionalized with primary amine, hydroxyl, and carboxyl groups were prepared and characterized. An analysis by Fourier-transform infrared (FT-IR) spectroscopy showed that PHEMA chains were grafted to the functionalized CNTs. X-ray photoelectron spectroscopy suggested that the grafting reaction was viable. The morphology of the prepared nanocomposites studied by field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) showed significant changes with respect to the observed for pure PHEMA. The thermal behavior of the nanocomposites studied by differential scanning calorimetry (DSC) revealed that the functionalized CNTs strongly affect the mobility of the PHEMA chains. Tests carried out by thermogravimetric analysis (TGA) were used to calculate the degree of grafting of the PHEMA chains. The ability of the prepared nanocomposites to inhibit the growth of the fungus Candida albicans and the bacteria Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli was evaluated. A reduced antifungal and antibacterial capacity of the prepared nanocomposites was determined.

Study of crosslinker size on the rheological properties of borate crosslinked guar gum

Borate crosslinked guar gum gels have played a vital role in stimulating oil and gas wells for many years; however, the high dosage of guar gum in the existing fracturing fluid will increase the cost and cause more damage to the reservoir and ultimately affect the effect of stimulation. In this study, borate esters are modified onto polyethyleneimine (PEI) of different molecular weights, affording organic borate crosslinkers of different sizes. By analyzing the effect of crosslinker size on gel rheology, sand-carrying properties, and microstructure, it is observed that the crosslinking efficiency is most significantly enhanced when the crosslinker size is similar to the diameter of the guar gum molecules. This makes it possible for the gel to maintain good performance at low polymer concentrations and meet the performance requirements of fracturing, which provides new ideas for developing the next generation of economical, clean, and green fracturing fluids.

Self-cross-linked starch/chitosan hydrogel as a biocompatible vehicle for controlled release of drug

A facile one-pot approach was adopted to prepare a polysaccharide-based hydrogel of oxidized starch (OS)-chitosan. The synthetic monomer-free, eco-friendly hydrogel was prepared in an aqueous solution and employed for controlled drug release application. The starch was first oxidized under mild conditions to prepare its bialdehydic derivative. Subsequently, the amino group-containing a modified polysaccharide, "chitosan" was introduced on the backbone of OS via a dynamic Schiff-base reaction. The bio-based hydrogel was obtained via a one-pot in-situ reaction, where functionalized starch acts as a macro-cross-linker that contributes structural stability and integrity to the hydrogel. The introduction of chitosan contributes stimuli-responsive properties and thus pH-sensitive swelling behavior was obtained. The hydrogel showed its potential as a pH-dependent controlled drug release system and a maximum of 29 h sustained release period was observed for ampicillin sodium salt drug. In vitro studies confirmed that the prepared drug-loaded hydrogels showed excellent antibacterial ability. Most importantly, the hydrogel could find potential use in the biomedical field due to its facile reaction conditions, biocompatibility along with the controlled releasing ability of the encapsulated drug.

pH and Thermoresponsive PNIPAm-co-Polyacrylamide Hydrogel for Dual Stimuli-Responsive Controlled Drug Delivery

The therapeutic delivery system with dual stimuli-responsiveness has attracted attention for drug delivery to target sites. In this study, we used free radical polymerization to develop a temperature and pH-responsive poly(N-isopropyl acrylamide)-co-poly(acrylamide) (PNIPAM-co-PAAm). PNIPAm-co-PAAm copolymer by reacting with N-isopropyl acrylamide (NIPAm) and acrylamide (Am) monomers. In addition, the synthesized melamine-glutaraldehyde (Mela-Glu) precursor was used as a cross-linker in the production of the melamine cross-linked PNIPAm-co-PAAm copolymer hydrogel (PNIPAm-co-PAAm-Mela HG) system. The temperature-responsive phase transition characteristics of the resulting PNIPAM-co-PAAm-Mela HG systems were determined. Furthermore, the pH-responsive drug release efficiency of curcumin was investigated under various pH and temperature circumstances. Under the combined pH and temperature stimuli (pH 5.0/45 °C), the PNIPAm-co-PAAm-Mela HG demonstrated substantial drug loading (74%), and nearly complete release of the loaded drug was accomplished in 8 h. Furthermore, the cytocompatibility of the PNIPAm-co-PAAm-Mela HG was evaluated on a human liver cancer cell line (HepG2), and the findings demonstrated that the prepared PNIPAm-co-PAAm-Mela HG is biocompatible. As a result, the PNIPAm-co-PAAm-Mela HG system might be used for both pH and temperature-stimuli-responsive drug delivery.

Application Progress of Modified Chitosan and Its Composite Biomaterials for Bone Tissue Engineering

In recent years, bone tissue engineering (BTE), as a multidisciplinary field, has shown considerable promise in replacing traditional treatment modalities (i.e., autografts, allografts, and xenografts). Since bone is such a complex and dynamic structure, the construction of bone tissue composite materials has become an attractive strategy to guide bone growth and regeneration. Chitosan and its derivatives have been promising vehicles for BTE owing to their unique physical and chemical properties. With intrinsic physicochemical characteristics and closeness to the extracellular matrix of bones, chitosan-based composite scaffolds have been proved to be a promising candidate for providing successful bone regeneration and defect repair capacity. Advances in chitosan-based scaffolds for BTE have produced efficient and efficacious bio-properties via material structural design and different modifications. Efforts have been put into the modification of chitosan to overcome its limitations, including insolubility in water, faster depolymerization in the body, and blood incompatibility. Herein, we discuss the various modification methods of chitosan that expand its fields of application, which would pave the way for future applied research in biomedical innovation and regenerative medicine.

pHEMA: An Overview for Biomedical Applications

Poly(2-hydroxyethyl methacrylate) (pHEMA) as a biomaterial with excellent biocompatibility and cytocompatibility elicits a minimal immunological response from host tissue making it desirable for different biomedical applications. This article seeks to provide an in-depth overview of the properties and biomedical applications of pHEMA for bone tissue regeneration, wound healing, cancer therapy (stimuli and non-stimuli responsive systems), and ophthalmic applications (contact lenses and ocular drug delivery). As this polymer has been widely applied in ophthalmic applications, a specific consideration has been devoted to this field. Pure pHEMA does not possess antimicrobial properties and the site where the biomedical device is employed may be susceptible to microbial infections. Therefore, antimicrobial strategies such as the use of silver nanoparticles, antibiotics, and antimicrobial agents can be utilized to protect against infections. Therefore, the antimicrobial strategies besides the drug delivery applications of pHEMA were covered. With continuous research and advancement in science and technology, the outlook of pHEMA is promising as it will most certainly be utilized in more biomedical applications in the near future. The aim of this review was to bring together state-of-the-art research on pHEMA and their applications.

The Mechanisms and the Applications of Antibacterial Polymers in Surface Modification on Medical Devices

Medical device contamination caused by microbial pathogens such as bacteria and fungi has posed a severe threat to the patients' health in hospitals. Due to the increasing resistance of pathogens to antibiotics, the efficacy of traditional antibiotics treatment is gradually decreasing for the infection treatment. Therefore, it is urgent to develop new antibacterial drugs to meet clinical or civilian needs. Antibacterial polymers have attracted the interests of researchers due to their unique bactericidal mechanism and excellent antibacterial effect. This article reviews the mechanism and advantages of antimicrobial polymers and the consideration for their translation. Their applications and advances in medical device surface coating were also reviewed. The information will provide a valuable reference to design and develop antibacterial devices that are resistant to pathogenic infections.

Decoupled pH- and Thermo-Responsive Injectable Chitosan/PNIPAM Hydrogel via Thiol-Ene Click Chemistry for Potential Applications in Tissue Engineering

Stimuli-responsive chitosan (CS) hydrogels exhibit great potential for drug delivery and tissue engineering; however, the structure of these stimuli-responsive CS hydrogels, such as dual pH- and thermo-responsive hydrogels, is difficult to control or needs additional crosslinking agents. Here, a new dual pH- and thermo-responsive hydrogel system is developed by combining pH-responsive C₆ -OH allyl-modified CS (OAL-CS) with thermo-responsive poly(N-isopropylacrylamide) (PNIPAM). The thiol groups in PNIPAM and the allyl groups in OAL-CS can rapidly form crosslinking hydrogel network by "thiol-ene" click chemistry under UV irradiation. As expected, the swelling ratio of the OAL-CS/PNIPAM hydrogel can be controlled by changing pH and temperature. Moreover, the hydrogel displays non-cytotoxic nature toward human bone marrow mesenchymal stem cells, and the histological analyses reveal the subcutaneous tissue with no signs of inflammation after 5 days of injection in vivo. The results indicate that the new OAL-CS/PNIPAM hydrogel has potential to serve as a smart injectable platform for application in drug delivery and tissue engineering.

Chitosan-induced Synergy for Extended Antimicrobial Potency and Enhanced In Vitro Drug Release of Free Base Ciprofloxacin Nanoplexes

BACKGROUND

Ciprofloxacin free base is practically insoluble in aqueous medium (0.0011 and 0.09 mg/mL at 25 and 37°C respectively). Its inorganic salt form (ciprofloxacin hydrochloride) is more soluble in water (1.35 mg/mL) however when administered orally, it exhibits decreased solubility in the stomach due to common ion effects. Ciprofloxacin free base was used in this study because of its greater hydrophobicity than its hydrochloride salt, which is required for effective permeability and potent antibacterial activity.

OBJECTIVE

The purpose of this study is to enhance oral solubility and bacterial cell permeability of the free base ciprofloxacin (CPX) using a single step CPX-chitosan (CT) selfassembly to form nanoplexes with organic counterions. It was envisioned that this would allow the delivery of larger amounts of active drug into the microorganisms.

METHODS

Ciprofloxacin-chitosan nanocomplex (nanoplex) was prepared using low energy electrostatic self-assembly technique previously described. Formation of eutectic nanoplex was confirmed using FTIR, DSC, TGA and SEM. The saturated solubility, in vitro release kinetics and mechanism of drug release were determined using mathematical models. Potency and synergism were determined from the inhibition zones, minimum inhibitory concentration (MIC) and Fractional Inhibitory Concentration (FIC) of the nanoplexes using Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.

RESULTS

Formation of CPX-CT eutectic adduct polymeric nanoplexes was confirmed with FT-IR and DSC and SEM revealed the conversion of rod-like crystals of CPX (117 μm long) into spherical nanostructures (23-503 nm) dictated by pH, ionic strength and concentration of CT. The solubility of free base CPX increased to a maximum of 32.77 mg/mL compared to 0.0011-0.09 mg/mL reported in literature and dissolution efficiency increased to a maximum of 100% within 72 h. The synergistic effect of CT on antimicrobial activity of CPX was quantified, for the first time, using Fractional Inhibitory Concentration (FIC) of the nanoplexes. FIC was less than 0.5 in both Gram positive (0.031-0.250) and Gram negative (0.036-0.281) microorganisms used in this study, confirming synergistic enhancement of antimicrobial efficacy of CPX.

CONCLUSION

It is evident that the design of drug-polymer nanocomplex formulation provides a platform for the synergistic enhancement of therapeutic potency of antibiotics.

In vivo systemic toxicity assessment of an oxidized dextrin-based hydrogel and its effectiveness as a carrier and stabilizer of granular synthetic bone substitutes

The worldwide incidence of bone disorders is raising, mainly due to aging population. The lack of effective treatments is pushing the development of synthetic bone substitutes (SBSs). Most ceramic-based SBSs commercially available display limited handling properties. Attempting to solve these issues and achieve wider acceptance by the clinicians, granular ceramics have been associated with hydrogels (HGs) to produce injectable/moldable SBSs. Dextrin, a low-molecular-weight carbohydrate, was used to develop a fully resorbable and injectable HG. It was first oxidized with sodium periodate and then cross-linked with adipic acid dihydrazide. The in vivo biocompatibility and safety of the dextrin-based HG was assessed by subacute systemic toxicity and skin sensitization tests, using rodent models. The results showed that the HG did not induce any systemic toxic effect, skin reaction, or genotoxicity, neither impaired the bone repair/regeneration process. Then, the HG was successfully combined with granular bone substitute, registered as Bonelike (250-500 μm) to obtain a moldable/injectable SBS, which was implanted in tibial fractures in goats for 3 and 6 weeks. The obtained results showed that HG allowed the stabilization of the granules into the defect, ensuring effective handling, and molding properties of the formulation, as well as an efficient cohesion of the granules. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1678-1689, 2019.

Polysaccharide and poly(methacrylic acid) based biodegradable elastomeric biocompatible semi-IPN hydrogel for controlled drug delivery

Nanoparticles embedded semi-interpenetrating (semi-IPNs) polymeric hydrogels with enhanced mechanical toughness and biocompatibility could have splendid biomedical acceptance. Here we propose poly(methacrylic acid) grafted polysaccharide based semi-IPNs filled with nanoclay via in situ Michael type reaction associated with covalent crosslinking with N,N-methylenebisacrylamide (MBA). The effect of nanoclay in the semi-IPN hydrogel has been investigated which showed significant improvement of mechanical robustness. Meanwhile, the hydrogels showed reversible ductility up to 70% in response to cyclic loading-unloading cycle which is an obvious phenomenon of rubber-like elasticity. The synthesized semi-IPN hydrogel show biodegradability and non-cytotoxic nature against human cells. The live-dead assay showed that the prepared hydrogel is a viable platform for cell growth without causing severe cell death. The in vitro drug release study in psychological pH (pH = 7.4) reveals that the controlled drug release phenomena can be tuned by simulating the environment pH. Such features in a single hydrogel assembly can propose this as high performance; biodegradable and non-cytotoxic 3D scaffold based promising biomaterial for tissue engineering.

Antimicrobial hydrogels: promising materials for medical application

The rapid emergence of antibiotic resistance in pathogenic microbes is becoming an imminent global public health problem. Local application of antibiotics might be a solution. In local application, materials need to act as the drug delivery system. The drug delivery system should be biodegradable and prolonged antibacterial effect should be provided to satisfy clinical demand. Hydrogel is a promising material for local antibacterial application. Hydrogel refers to a kind of biomaterial synthesized by a water-soluble natural polymer or a synthesized polymer, which turns into gel according to the change in different signals such as temperature, ionic strength, pH, ultraviolet exposure etc. Because of its high hydrophilicity, unique three-dimensional network, fine biocompatibility and cell adhesion, hydrogel is one of the suitable biomaterials for drug delivery in antimicrobial areas. In this review, studies from the past 5 years were reviewed, and several types of antimicrobial hydrogels according to different ingredients, different preparations, different antimicrobial mechanisms, different antimicrobial agents they contained and different applications, were summarized. The hydrogels loaded with metal nanoparticles as a potential method to solve antibiotic resistance were highlighted. Finally, future prospects of development and application of antimicrobial hydrogels are suggested.

Cross-linked β-cyclodextrin and carboxymethyl cellulose hydrogels for controlled drug delivery of acyclovir

To explore the potential role of polymers in the development of drug-delivery systems, this study investigated the use of β-cyclodextrin (β-CD), carboxymethyl cellulose (CMC), acrylic acid (AA) and N’ N’-methylenebis-acrylamide (MBA) in the synthesis of hydrogels for controlled drug delivery of acyclovir (ACV). Different proportions of β-CD, CMC, AA and MBA were blended with each other to fabricate hydrogels via free radical polymerization technique. Fourier transform infrared spectroscopy (FTIR) revealed successful grafting of components into the polymeric network. Thermal and morphological characterization confirmed the formation of thermodynamically stable hydrogels having porous structure. The pH-responsive behaviour of hydrogels has been documented by swelling dynamics and drug release behaviour in simulated gastrointestinal fluids. Drug release kinetics revealed controlled release behaviour of the antiviral drug acyclovir in developed polymeric network. Cross-linked β-cyclodextrin and carboxymethyl cellulose hydrogels can be used as promising candidates for the design and development of controlled drug-delivery systems.

Synthesis and characterization of biodegradable copolymer derived from dextrin and poly(vinyl acetate) via atom transfer radical polymerization

This article reports the development of a dextrin-based amphiphilic biodegradable graft copolymer (Dxt-g-pVAc) via atom transfer radical polymerization (ATRP).

Dextrin and poly(lactide)-based biocompatible and biodegradable nanogel for cancer targeted delivery of doxorubicin hydrochloride

Herein, we report the development and application of a novel biocompatible, chemically crosslinked nanogel for use in anticancer drug delivery.

Photo-irradiation paradigm: Mapping a remarkable facile technique used for advanced drug, gene and cell delivery

Undoubtedly, the progression of photo-irradiation technique has provided a smart engineering tool for the state-of-the-art biomaterials that guide the biomedical and therapeutic domains for promoting the modern pharmaceutical industry. Many investigators had exploited such a potential technique to create/ameliorate numerous pharmaceutical carriers. These carriers show promising applications that vary from small drug to therapeutic protein delivery and from gene to living cell encapsulation design. Harmony between the properties of precisely engineered precursors and the formed network structure broadens the investigator's intellect for both brilliant creations and effective applications. As well, controlling photo-curing at the formulation level, through manipulating the absorption of light stimuli, photoinitiator system and photo-responsive precursor, facilitates the exploration of novel distinctive biomaterials. Discussion of utilizing different photo-curing procedures in designing/formulation of different pharmaceutical carriers is the main emphasis of this review. In addition, recent applications of these intelligent techniques in targeted, controlled, and sustained drug delivery with understanding of photo-irradiation concept and mechanism are illustrated.

Stimulus-Responsive, Biodegradable, Biocompatible, Covalently Cross-Linked Hydrogel Based on Dextrin and Poly(N-isopropylacrylamide) for in Vitro/in Vivo Controlled Drug Release

A novel stimulus-sensitive covalently cross-linked hydrogel derived from dextrin, N-isopropylacrylamide, and N,N'-methylene bis(acrylamide) (c-Dxt/pNIPAm), has been synthesized via Michael type addition reaction for controlled drug release application. The chemical structure of c-Dxt/pNIPAm has been confirmed through Fourier transform infrared (FTIR) spectroscopy and (1)H and (13)C NMR spectral analyses. The surface morphology of the hydrogel has been studied by field emission scanning electron microscopic (FE-SEM) and environmental scanning electron microscopic (E-SEM) analyses. The stimulus responsiveness of the hydrogel was studied through equilibrium swelling in various pH media at 25 and 37 °C. Rheological study was performed to measure the gel strength and gelation time. Noncytotoxicity of c-Dxt/pNIPAm hydrogel has been studied using human mesenchymal stem cells (hMSCs). The biodegradability of c-Dxt/pNIPAm was confirmed using hen egg lysozyme. The in vitro and in vivo release studies of ornidazole and ciprofloxacin imply that c-Dxt/pNIPAm delivers both drugs in a controlled way and would be an excellent alternative for a dual drug carrier. The FTIR, powder X-ray diffraction (XRD), and UV-vis-near infrared (NIR) spectra along with the computational study predict that the drugs remain in the matrix through physical interaction. A stability study signifies that the drugs (ornidazole ∼97% and ciprofloxacin ∼98%) are stable in the tablet formulations for up to 3 months.

Dextrin and poly(acrylic acid)-based biodegradable, non-cytotoxic, chemically cross-linked hydrogel for sustained release of ornidazole and ciprofloxacin

Herein, novel biodegradable, stimulus-responsive, chemically cross-linked and porous hydrogel has been synthesized to evaluate its applicability as an efficient carrier for sustained release of ornidazole and ciprofloxacin. The cross-linked hydrogel (c-Dxt/pAA) has been developed from dextrin and poly(acrylic acid) using N,N'-methylene bis(acrylamide) cross-linker via Michael-type addition reaction. With the variation of reaction parameters, various c-Dxt/pAA hydrogels have been synthesized to optimize the best one. c-Dxt/pAA hydrogel has been characterized using various physicochemical characterization techniques. The hydrogel demonstrates significant pH and temperature sensitivity. Gel characteristics and gel kinetics have been performed through the measurement of rheological parameters. The hydrogel shows noncytotoxic behavior toward human mesenchymal stem cells. Biodegradation study predicts that c-Dxt/pAA is degradable in nature. The in vitro release of ornidazole and ciprofloxacin suggests that the hydrogel released both the drugs in a controlled manner with extensive stability up to 3 months. The results suggest that c-Dxt/pAA is probably a promising candidate for controlled release of ornidazole and ciprofloxacin.

Modified biopolymer-dextrin based crosslinked hydrogels: application in controlled drug delivery

This review describes hydrogels and their classifications along with the synthesis and properties of biopolymer-dextrin based crosslinked hydrogels towards potential application in controlled drug delivery.