In situ formed aldehyde-modified hyaluronic acid hydrogel with polyelectrolyte complexes of aldehyde-modified chondroitin sulfate and gelatin: An approach for minocycline delivery.

Polysaccharides like hyaluronan (HA) and chondroitin sulfate (CS) are native of the brain's extracellular matrix crucial for myelination and brain maturation. Despite extensive research on HA and CS as drug delivery systems (DDS), their high water solubility limits their application as drug carriers. This study introduces an injectable DDS using aldehyde-modified hyaluronic acid (HAOX) hydrogel containing polyelectrolyte complexes (PEC) formed with calcium, gelatin, and either CS or aldehyde-modified CS (CSOX) to deliver minocycline for Multiple Sclerosis therapy. PECs with CSOX enable covalent crosslinking to HAOX, creating immobilized PECs (HAOX_PECOX), while those with CS remain unbound (HAOX_PECS). The in situ forming DDS can be administered via a 20 G needle, with rapid gelation preventing premature leakage. The system integrates into an implanted device for minocycline release through either Fickian or anomalous diffusion, depending on PEC immobilization. HAOX_PECOX reduced burst release by 88 %, with a duration of 127 h for 50 % release. The DDS exhibited an elastic modulus of 3800 Pa and a low swelling ratio (0-1 %), enabling precise control of minocycline release kinetics. Released minocycline reduced IL-6 secretion in the Whole Blood Monocytes Activation Test, suggesting that DDS formation may not alter the biological activity of the loaded drug.

ZIF-8-based Nanoparticles for Inflammation Treatment and Oxidative Stress Reduction in Periodontitis.

Periodontitis, an inflammatory bone resorption disease associated with dental plaque, poses significant challenges for effective treatment. In this study, we developed Mino@ZIF-8 nanoparticles inspired by the periodontal microenvironment and the unique properties of zeolitic imidazolate framework 8, aiming to address the complex pathogenesis of periodontitis. Transcriptome analysis revealed the active engagement of Mino@ZIF-8 nanoparticles in innate and adaptive inflammatory host defense and cellular metabolic remodeling. Through sustained release of the anti-inflammatory and antibacterial agent minocycline hydrochloride (Mino) and the generation of Zn2+ with pro-antioxidant effects during degradation, Mino@ZIF-8 nanoparticles synergistically alleviate inflammation and oxidative damage. Notably, our study focuses on the pivotal role of zinc ions in mitochondrial oxidation protection. Under lipopolysaccharide (LPS) stimulation, periodontal ligament cells undergo a metabolic shift from oxidative phosphorylation (OXPHOS) to glycolysis, leading to reduced ATP production and increased reactive oxygen species levels. However, Zn2+ effectively rebalances the glycolysis-OXPHOS imbalance, restoring cellular bioenergetics, mitigating oxidative damage, rescuing impaired mitochondria, and suppressing inflammatory cytokine production through modulation of the AKT/GSK3ß/NRF2 pathway. This research not only presents a promising approach for periodontitis treatment but also offers novel therapeutic opportunities for zinc-containing materials, providing valuable insights into the design of biomaterials targeting cellular energy metabolism regulation.

Near-infrared light-boosted antimicrobial activity of minocycline/hyaluronan/carbon nanohorn composite toward peri-implantitis treatments.

Dental implant therapy is a reliable treatment for replacing missing teeth. However, as dental implants become more widely used, peri-implantitis increasingly has become a severe complication, making successful treatment more difficult. As a result, the development of effective drug delivery systems (DDSs) and treatments for peri-implantitis are urgently needed. Carbon nanohorns (CNHs) are carbon nanomaterials that have shown promise for use in DDSs and have photothermal effects. The present study exploited the unique properties of CNHs to develop a phototherapy employing a near-infrared (NIR) photoresponsive composite of minocycline, hyaluronan, and CNH (MC/HA/CNH) for peri-implantitis treatments. MC/HA/CNH demonstrated antibacterial effects that were potentiated by NIR-light irradiation, a property that was mediated by photothermal-mediated drug release from HA/CNH. These antibacterial effects persisted even following 48 h of dialysis, a promising indication for the clinical use of this material. We propose that the treatment of peri-implantitis using NIR and MC/HA/CNH, in combination with surgical procedures, might be employed to target relatively deep affected areas in a timely and efficacious manner. We envision that this innovative approach will pave the way for future developments in implant therapy.

Abalone-Inspired Adhesive and Photo-Responsive Microparticle Delivery Systems for Periodontal Drug Therapy.

Antibiotics provide promising strategies for treating periodontitis, while their delivery and controllable release with desired oral retention remain challenging. Here, inspired by the unique suction-cup structures of abalones, a novel adhesive and photo-responsive microparticle (MP) delivery system is developed to treat periodontitis through microfluidic electrospray technology. Such MPs are generated by quickly ionic cross-linking of sodium alginate together with photo-curing of poly(ethylene glycol) diacrylate of the distorted microfluidic droplets during their high-speed dropping into calcium chloride solution. Attributing to their unique concave structures, the abalone-inspired MPs exhibit desired underwater adhesion ability and stability under running water. In addition, due to the loading of antibiotics minocycline hydrochloride and near-infrared (NIR)-responsive black phosphorus during their fabrication, the resultant MPs can not only eradicate bacteria directly, but also realize a controllable and effective drug release upon NIR irradiation. Based on these features, it is demonstrated from in vivo periodontitis that the abalone-inspired MPs are firmly adhesive and can controlled-release drugs on the tooth, and thus have outstanding antibacterial efficacy against Porphyromonas gingivalis. These results indicate the particular values of the abalone-inspired MPs for oral-related disease treatment.

Application of iron oxide nanoparticles to control the release of minocycline for the treatment of glioblastoma.

Background: The utilization of iron oxide nanoparticles (Fe3O4 NPs) to control minocycline release rates from poly(lactic-co-glycolic acid) scaffolds fabricated from an easy/economical technique is presented. Results & methodology: A larger change in temperature and amount of minocycline released was observed for scaffolds with higher amounts of Fe3O4 NPs, demonstrating that nanoparticle concentration can control heat generation and minocycline release. Temperatures near a polymer's glass transition temperature can result in the polymer's chain becoming more mobile and thus increasing drug diffusion out of the scaffold. Elevated temperature and minocycline released from the scaffold can work synergistically to enhance glioblastoma cell death. Conclusion: This study suggests that Fe3O4 NPs are promising materials for controlling minocycline release from polymeric scaffolds by magnetic hyperthermia for the treatment of glioblastoma.

Strategies to better treat glioblastoma: antiangiogenic agents and endothelial cell targeting agents.

Glioblastoma multiforme (GBM) is the most prevalent and aggressive form of glioma, with poor prognosis and high mortality rates. As GBM is a highly vascularized cancer, antiangiogenic therapies to halt or minimize the rate of tumor growth are critical to improving treatment. In this review, antiangiogenic therapies, including small-molecule drugs, nucleic acids and proteins and peptides, are discussed. The authors further explore biomaterials that have been utilized to increase the bioavailability and bioactivity of antiangiogenic factors for better antitumor responses in GBM. Finally, the authors summarize the current status of biomaterial-based targeting moieties that target endothelial cells in GBM to more efficiently deliver therapeutics to these cells and avoid off-target cell or organ side effects.

Hybrid Hydrogels for Synergistic Periodontal Antibacterial Treatment with Sustained Drug Release and NIR-Responsive Photothermal Effect.

BACKGROUND: Periodontal pathogenic bacteria promote the destruction of periodontal tissues and cause loosening and loss of teeth in adults. However, complete removal of periodontal pathogenic bacteria, at both the bottom of the periodontal pocket and the root bifurcation area, remains challenging. In this work, we explored a synergistic antibiotic and photothermal treatment, which is considered an alternative strategy for highly efficient periodontal antibacterial therapy. METHODS: Mesoporous silica (MSNs) on the surface of Au nanobipyramids (Au NBPs) were designed to achieve the sustained release of the drug and photothermal antibacterials. The mesoporous silica-coated Au NBPs (Au NBPs@SiO2) were mixed with gelatin methacrylate (GelMA-Au NBPs@SiO2). Au NBPs@SiO2 and GelMA-Au NBPs@SiO2 hybrid hydrogels were characterized, and the drug content and photothermal properties in terms of the release profile, bacterial inhibition, and cell growth were investigated. RESULTS: The GelMA-Au NBPs@SiO2 hybrid hydrogels showed controllable minocycline delivery, and the drug release rates increased under 808 nm near-infrared (NIR) light irradiation. The hydrogels also exhibited excellent antibacterial properties, and the antibacterial efficacy of the antibiotic and photothermal treatment was as high as 90% and 66.7% against Porphyromonas gingivalis (P. gingivalis), respectively. Moreover, regardless of NIR irradiation, cell viability was over 80% and the concentration of Au NBPs@SiO2 in the hybrid hydrogels was as high as 100 µg/mL. CONCLUSION: We designed a new near-infrared light (NIR)-activated hybrid hydrogel that offers both sustained release of antibacterial drugs and photothermal treatment. Such sustained release pattern yields the potential to rapidly eliminate periodontal pathogens in the periodontal pocket, and the photothermal treatment maintains low bacterial retention after the drug treatment.

Controlled release minocycline-lipid-complex extrudates for the therapy of periodontitis with enhanced flexibility.

We describe the development of flexible minocycline-lipid-complex extrudates with optimized mechanical and drug release properties. These extrudates contain a minocycline - magnesium stearate chelate complex with a higher stability in aqueous media, which has now been incorporated in a PEG-PLGA (polyethylene glycol - poly(lactic-co-glycolic acid)) matrix. PEG 1500 has been utilized in different concentrations to serve as plasticizer. The novel formulations have been characterized by texture analysis, X-Ray powder diffraction (XRPD) and differential scanning calorimetry (DSC). Extrudates with a reduced diameter of 300 µm (previously 600 µm) were introduced, and a more sensitive quantification method with a tandem-mass spectrometry detector was developed. From all tested formulations, the extrudates consisting of Expansorb DLG 50 - 6P (PEG-PLGA, molar weight 30-60 kDa) paired with 10% PEG 1500 emerged as best formulation. These extrudates feature a drug content of 11.5% and a controlled release over at least 42 days. The release profile is without a lag time and shows initially a slightly higher release rate, which is desired. Compared to previous developments, the extrudates now offer a high flexibility combined with a large mechanical resilience, which will ease the handling and administration.

Effects of protein-protein interface disruptors at the ligand of the glucocorticoid-induced tumor necrosis factor receptor-related gene (GITR).

The tumor necrosis factor (TNF) superfamily (TNFSF) includes about thirty structurally related receptors (TNFSFRs) and about twenty protein ligands that bind to one or more of these receptors. Receptors of the tumor necrosis factor (TNF) superfamily (TNFSFRs) are pharmacological targets for treatment of inflammatory and autoimmune diseases. Currently, drugs targeting TNFSFR signaling are biological drugs (monoclonal antibodies, decoy receptors) aimed at binding and sequestering TNFSFR ligands. The glucocorticoid-induced tumor necrosis factor receptor-related gene (GITR) signaling is involved in a series of inflammatory and autoimmune diseases, such as rheumatoid arthritis and Crohn's disease. Our study aimed at repurposing FDA approved small molecules as protein-protein disruptors at the GITR ligand (GITRL) trimer, in order to inhibit the binding of GITRL to its receptor (GITR). A structure based molecular modeling approach was carried out to identify, through high throughput virtual screening, GITRL monomer-monomer disruptors. We used a database of ~8,000 FDA approved drugs, and after virtual screening, we focused on two hit compounds, minocycline and oxytetracycline. These two compounds were tested for their capability to modulate IL-17, IL-21 and RORγT expression in T lymphocytes, isolated from wild-type and GITR knock-out (GITR-/-) mice. Minocycline showed immunomodulatory effects specific to GITR activation and could represent a novel pharmacological tool to treat inflammatory diseases.

Fabrication of biocompatible antibacterial nanowafers based on HNT/PVA nanocomposites loaded with minocycline for burn wound dressing.

Bacterial infections of burn wounds are a significant problem that usually slows or stops the process of burn wounds healing. The use of topical antibiotics based on a novel drug delivery system could overcome the limitations of burn wound healing. In this work, the development of new wound dressings based on nanocomposite film of polyvinyl alcohol (PVA) and halloysite nanotubes (HNT) for the delivery of minocycline was investigated. These elastomeric nanocomposites were prepared based on HNT surface modification by APTES and then PVA coating by LbL strategy. The resulting nanocomposites were characterized by FT-IR, XRD, zeta potential, Tg analysis, FESEM, and antibacterial studies. The biodegradability and water uptake of the film were evaluated, the results of which revealed the absorption of scarring and non-degradation of the nanocomposite during treatment. Because minocycline decomposes by light, increasing photostability was another goal that was achieved. The release profile of the drug from the nanocomposite was studied, and it was found to be consistent with the Korsmeyer-Peppas model. In-vitro studies showed the antibacterial effect of nanocomposite on exposure to Gram-positive and Gram-negative bacteria. Due to the properties of the resulting nanocomposite film, it can be considered as a promising candidate for wound healing. In-vivo studies, cell culture, neuroprotective and anti-inflammatory effects may be investigated to develop this wound dressing in the future.

Local delivery of minocycline-loaded PLGA nanoparticles from gelatin-coated neural implants attenuates acute brain tissue responses in mice.

BACKGROUND: Neural interfaces often elicit inflammatory responses and neuronal loss in the surrounding tissue which adversely affect the function and longevity of the implanted device. Minocycline, an anti-inflammatory pharmaceutics with neuroprotective properties, may be used for reducing the acute brain tissue responses after implantation. However, conventional administration routes require high doses which can cause adverse systemic side effects. Therefore, the aim of this study was to develop and evaluate a new drug-delivery-system for local and sustained administration of minocycline in the brain. METHODS: Stainless steel needles insulated with Parylene-C were dip-coated with non-crosslinked gelatin and minocycline-loaded PLGA nanoparticles (MC-NPs) were incorporated into the gelatin-coatings by an absorption method and subsequently trapped by drying the gelatin. Parylene-C insulated needles coated only with gelatin were used as controls. The expression of markers for activated microglia (CD68), all microglia (CX3CR1-GFP), reactive astrocytes (GFAP), neurons (NeuN) and all cell nuclei (DAPI) surrounding the implantation sites were quantified at 3 and 7 days after implantation in mice. RESULTS: MC-NPs were successfully incorporated into gelatin-coatings of neural implants by an absorption method suitable for thermosensitive drug-loads. Immunohistochemical analysis of the in vivo brain tissue responses, showed that MC-NPs significantly attenuate the activation of microglial cells without effecting the overall population of microglial cells around the implantation sites. A delayed but significant reduction of the astrocytic response was also found in comparison to control implants. No effect on neurons or total cell count was found which may suggest that the MC-NPs are non-toxic to the central nervous system. CONCLUSIONS: A novel drug-nanoparticle-delivery-system was developed for neural interfaces and thermosensitive drug-loads. The local delivery of MC-NPs was shown to attenuate the acute brain tissue responses nearby an implant and therefore may be useful for improving biocompatibility of implanted neuro-electronic interfaces. The developed drug-delivery-system may potentially also be used for other pharmaceutics to provide highly localized and therefore more specific effects as compared to systemic administration.

Extrudates of lipophilic tetracycline complexes: A new option for periodontitis therapy.

The objective of this study was to develop an improved drug delivery system for the local antimicrobial treatment of periodontitis, that offers enhanced drug stability, easy application and controlled release over several weeks. Chelate complexes consisting of a tetracycline antibiotic and a fatty acid salt were developed. Minocycline and doxycycline were paired with magnesium- and calcium stearate in different molar ratios. These chelate complexes stabilize the active pharmaceutical ingredient and enable the incorporation into a PLGA (poly(lactic-co-glycolic acid)) polymer matrix via hot melt extrusion. The chelate complexes were characterized via UV/Vis- and IR-spectroscopy. A high antibiotic activity of the complex was observed in a disc diffusion test. The drug complex was mixed with different PLGA-polymers and cryomilled in advance of the extrusion. The hot melt extrusion yielded homogeneous extrudates with a diameter from 600 to 900 µm. They contain 11.5% of minocycline, are adjustable in length and are easy to handle. In vitro release studies revealed a controlled release of the drug over 42 days. In conclusion, the developed extrudates are promising systems to improve the treatment of periodontitis.

A novel wound dressing consisting of PVA-SA hybrid hydrogel membrane for topical delivery of bacteriophages and antibiotics.

The emergence of antibiotic-resistant pathogens has made the treatment of infected burn wounds even more problematical than the pre-antibiotic era. Phage therapy is now being considered a promising treatment options to fight against antibiotic resistant pathogens. Hence, we introduce a novel PVA-SA hydrogel based wound dressing system for topical delivery of bacteriophages and antibiotic to treat infected burn injuries. Hydrogel membrane provides wound healing environment while surface absorbed bacteriophages/antibiotic takes care of the local infection. Different blends of PVA and SA were crosslinked by boric acid and calcium ions to form the hydrogel membrane and assessed for ideal wound dressing properties. 1:2 blended PVA: SA membrane displayed highest swelling index, gel fraction, protein adsorption, hemocompatibility and best mechanical properties among the 3 blends studied in this study. The selected membrane was further characterised by FTIR, FESEM and TGA. Overall, self-adherent, antibacterial and biocompatible membrane was obtained as revealed by the in-vitro antibacterial assays, elution assays and cell cytotoxicity assays. The in-vivo potential was evaluated using MRSA-infected murine burn wound model revealing significant bacterial reduction, wound contraction and reduced inflammation in membrane treated groups in comparison to control group. The dual coated hydrogel membrane delivering both MR10 phage and minocycline proved to be better treatment strategy to treat the resistant burn wound infection rather than phage and antibiotic alone.

Preparation and Properties of Minocycline-Loaded Carboxymethyl Chitosan Gel/Alginate Nonwovens Composite Wound Dressings.

As derivatives from marine natural biomaterials, alginate-based and chitosan-based biomaterials are commonly used in wound dressings. Calcium alginate fiber (CAF) dressings possess excellent absorption and unique gel forming performance, but the low bioactivity limits its application in wound healing. Carboxymethyl chitosan (CM-Chit) has excellent antibacterial activity, but the gel structure with weak mechanical properties restricts its application. In this study, minocycline (Mino)/CM-Chit solution was coated on the surface of plasma treated CAF needle-punched nonwovens, and then Mino loaded CM-Chit gel/CAF nonwovens composite dressings were fabricated by EDC/NHS (1-3-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide) crosslinking. The dressings had a porous composite structure, which allowed them to quickly absorb and store a large number of wound exudates. Skin-like tensile performance allowed the dressings to provide a better healing environment. Antibacterial assay against Escherichia coli and Staphylococcus aureus indicated that the addition of Mino significantly improved the antibacterial activity of the wound dressings. The tight structure of CM-Chit gel prevented the burst release of Mino so that the dressings had antibacterial activity in a certain period of release time. Cell culture assay showed that the dressings had excellent cell biocompatibility. As new functional dressings, the prepared composite dressings had excellent potential in the clinical healing of wounds.

An enzyme-responsive membrane for antibiotic drug release and local periodontal treatment.

Periodontitis is a chronic, destructive inflammatory disease that injures tooth- supporting tissues, eventually leading to tooth loss. Complete eradication of periodontal pathogenic microorganisms is fundamental to allow periodontal healing and commonly precedes periodontal tissue regeneration. To address this challenge, we report a strategy for developing an enzyme-mediated periodontal membrane for targeted antibiotic delivery into infectious periodontal pockets; the unique components of the membrane will also benefit periodontal alveolar bone repair. In this approach, a chitosan membrane containing polyphosphoester and minocycline hydrochloride (PPEM) was prepared. Physical, morphological, and ultrastructural analyses were carried out in order to assess cellular compatibility, drug release and antibacterial activity in vitro. Additionally, the functionality of the PPEM membrane was evaluated in vivo with a periodontal defect model in rats. The results confirm that the PPEM membrane exhibits good physical properties with excellent antibacterial activity and successfully promotes periodontal tissue repair, making it promising for periodontal treatment.

Minocycline-loaded calcium polyphosphate glass microspheres as a potential drug-delivery agent for the treatment of periodontitis.

Background: Periodontitis is an inflammatory disease with a bacterial etiology that affects the supporting structures of the teeth and is a major cause of tooth loss. The objective of this study was to investigate the drug loading and in vitro release of minocycline from novel calcium polyphosphate microspheres intended for use in treating periodontitis. Methods: Calcium polyphosphate coacervate, produced by a precipitation reaction of calcium chloride and sodium polyphosphate solutions, was loaded with minocycline and subsequently used to produce microspheres by an emulsion/solvent extraction technique. Microspheres classified by size were subjected to a 7-day elution in a Tris-buffer solution under dynamic conditions. The physicochemical characteristics of the drug-loaded microspheres were investigated using scanning electron microscopy, particle size analysis, Phosphorus-31 Nuclear Magnetic Resonance spectroscopy, and Inductively Coupled Plasma Optical Emission Spectroscopy. Drug loading and release were determined using ultraviolet -visible (UV/VIS) spectrophotometry. Results: Minocycline-loaded calcium polyphosphate microspheres of varying size were successfully produced, with small and large microspheres having volume mean diameters of 22 ± 1 µm and 193 ± 5 µm, respectively. Polyphosphate chain length and calcium to phosphorus mole ratio remained stable throughout microsphere production. Drug loading was 1.64 ± 0.16, 1.35 ± 0.55, and 0.84 ± 0.14 weight% for the coacervate and large and small microspheres, respectively, corresponding to mean encapsulation efficiencies of 81.7 ± 12.2 % and 50.9 ± 3.9 % for the large and small microspheres. Sustained drug release was observed in vitro over a clinically relevant 7-day period, with small and large microspheres exhibiting similar elution profiles. Antibiotic release generally followed microsphere degradation as measured by Ca and P ion release. Conclusions: This study demonstrated successful drug loading of calcium polyphosphate microspheres with minocycline. Furthermore, in vitro sustained release of minocycline over a 7-day period was observed, suggesting potential utility of this approach for treating periodontitis.

Regeneration of porous electrospun membranes embedding alumina nanoparticles saturated with minocycline by UV radiation.

A regeneration method for porous electrospun membranes embedding alumina nanoparticles saturated with minocycline was investigated by UV-LED system. The percentage of adsorption capacities before and after regeneration were used to evaluate regeneration efficiency. The PVDF and PVDF-Al2O3 fiber mats were prepared by electrospinning technique. Scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDS) analyses directly confirmed that Al2O3 nanoparticles were generally exposed to the surface of PVDF-Al2O3 fiber mats. Among them, PVDF-Al2O3 10% fiber mats can effectively adsorb minocycline (remove efficiency >97% in 18 h) with first-order rate constant k = 2.253 ±â€¯0.331 h-1. The sorption capacity can still keep 81% after five sorption/UV-regeneration circulations. Two successional stages may exist during regeneration: (i) transfer of minocycline from the surface of PVDF-Al2O3 fibers to the DI water, followed by the (ii) decomposition of this compound in aqueous solution by direct and indirect photolysis to yield the intermediate species. The desorption capacity and desorption percentage were 4.39 mg g-1 and 23.30% respectively. The regeneration yields were further enhanced to 94.20% by UV radiation. Minocycline was effectively degraded to intermediate products by direct and indirect photolysis, further degraded into CO2, H2O, and NOx by UV-generated ozone during regeneration. The results indicated that UV radiation was an effective method of regenerating PVDF-Al2O3 fiber mats with low energy requirements. The photochemical byproducts and the reaction sites during regeneration were also determined and recognized.

Self-Assembly of DNA-Minocycline Complexes by Metal Ions with Controlled Drug Release.

Here we reported a study of metal ions-assisted assembly of DNA-minocycline (MC) complexes and their potential application for controlling MC release. In the presence of divalent cations of magnesium or calcium ions (M2+), MC, a zwitterionic tetracycline analogue, was found to bind to phosphate groups of nucleic acids via an electrostatic bridge of phosphate (DNA)-M2+-MC. We investigated multiple parameters for affecting the formation of DNA-Mg2+-MC complex, including metal ion concentrations, base composition, DNA length, and single- versus double-stranded DNA. For different nitrogen bases, single-stranded poly(A)20 and poly(T)20 showed a higher MC entrapment efficiency of DNA-Mg2+-MC complex than poly(C)20 and poly(G)20. Single-stranded DNA was also found to form a more stable DNA-Mg2+-MC complex than double-stranded DNA. Between different divalent metal ions, we observed that the formation of DNA-Ca2+-MC complex was more stable and efficient than the formation of DNA-Mg2+-MC complex. Toward drug release, we used agarose gel to encapsulate DNA-Mg2+-MC complexes and monitored MC release. Some DNA-Mg2+-MC complexes could prolong MC release from agarose gel to more than 10 days as compared with the quick release of free MC from agarose gel in less than 1 day. The released MC from DNA-Mg2+-MC complexes retained the anti-inflammatory bioactivity to inhibit nitric oxide production from pro-inflammatory macrophages. The reported study of metal ion-assisted DNA-MC assembly not only increased our understanding of biochemical interactions between tetracycline molecules and nucleic acids but also contributed to the development of a highly tunable drug delivery system to mediate MC release for clinical applications.

Antibiotic-Containing Agarose Hydrogel for Wound and Burn Care.

Wound infections cause inflammation, tissue damage, and delayed healing that can lead to invasive infection and even death. The efficacy of systemic antibiotics is limited due to poor tissue penetration that is especially a problem in burn and blast wounds where the microcirculation is disrupted. Topical administration of antimicrobials is an attractive approach because it prevents infection and avoids systemic toxicity, while hydrogels are an appealing vehicle for topical drug delivery. They are easy to apply to the wound site by being injectable, the drug release properties can be controlled, and their many characteristics, such as biodegradation, mechanical strength, and chemical and biological response to stimuli can be tailored. Hydrogels also create a moist wound environment that is beneficial for healing. The purpose of this study was to formulate an agarose hydrogel that contains high concentrations of minocycline or gentamicin and study its characteristics. Subsequently, the minocycline agarose hydrogel was tested in a porcine burn model and its effect as a prophylactic treatment was studied. The results demonstrated that 0.5% agarose in water was the optimal concentration in terms of viscosity and pH. Bench testing at room temperature demonstrated that both antibiotics remained stable in the hydrogel for at least 7 days and both antibiotics demonstrated sustained release over the time of the experiment. The porcine burn experiment showed that prophylactic treatment with the agarose minocycline hydrogel decreased the burn depth and reduced the number of bacteria as efficiently as the commonly used silver sulfadiazine cream.

The allosteric modulation effects of doxycycline, minocycline, and their derivatives on the neuropeptide receptor PAC1-R.

Class B G-protein coupled receptors (GPCR) PAC1-R is a neuropeptide pituitary adenylate cyclase activating polypeptide (PACAP)-preferring receptor that mediates the effective neuroprotective activity. Based on our previous data showing that doxycycline and minocycline work as the positive allosteric modulator (PAM) of PAC1-R, we used computer molecular docking and isothermal titration calorimetry assay to further determine the bindings of doxycycline/minocycline's derivatives including tetracycline/tigecycline with the N-terminal extracellular domain of PAC1-R (PAC1-EC1). Then the cAMP assay combined with the PAC1-R natural agonist PACAP27 was used to confirm the possible PAM roles of the small-molecule antibiotics. The results showed that tetracycline/tigecycline had significant lower affinity to PAC1-EC1 than doxycycline/minocycline, which was consistent with their non-positive allosteric modulation activity on PAC1-R. Furthermore, by comparing the key residues contributing to the PAM binding with the predicted allosteric site in PAC1-EC1, we characterized four motifs contributing to PAM binding in PAC1-EC1. The site-directed mutation results showed that ASN60 played the most important role in the PAM binding of the small-molecule antibiotics, while ASP116 played a sensitive marginal role in the PAM binding. These results not only help to explain the clinical and experimental neuroprotective effects of doxycycline/minocycline, but also help to characterize the PAM binding site in PAC1-EC1, which will promote the screening and characterization of novel small-molecule PAMs targeting PAC1-EC1 with drug development potency in nerve system disease.