Injectable Drug Delivery System Research Articles

Rapamycin incorporating hydrogel improves the progression of osteoarthritis by inducing synovial macrophages polarization and reducing intra-articular inflammation

In the macrophage-specific mTORC1 signaling activation model, the synovial macrophages polarized toward M1, thus aggravating synovitis and progression of OA. Therefore, intra-articular injection of rapamycin, a classical mTORC1 inhibitor, may show great potential for alleviating synovitis and delaying cartilage destruction in osteoarthritis (OA). However, the durable retention of drugs in the joint cavity is still a critical issue to be addressed. Herein, we crosslinked the Poloxamer 407 and hyaluronic acid (P-HA) to prepare an injectable and thermo-responsive drug delivery system to durably retain rapamycin and dramatically magnify their therapeutic effects in OA management. The prepared P-HA hydrogel showed excellent biocompatibility with chondrocytes and fibroblasts, as well as possessed sustained rapamycin release profiles for 14 days. Intra-articular injection of this rapamycin-incorporated P-HA hydrogel indicated a positively effect on inducing the polarization of synovial macrophages from M1 to M2 phenotype and reducing synovial inflammation in OA. This strategy significantly decreased the pro-inflammatory cytokines (e.g., TNF-α, IL-1β, and IL-6) and increased the anti-inflammatory cytokine (e.g., IL-10) expression in the synovial tissues and synovial fluid. As a result, intra-articular injection of rapamycin-incorporated P-HA hydrogel significantly prevented cartilage destruction by inducing cartilage matrix formation, which suggesting a great potential for the management of OA.

The incorporated hydrogel of chitosan-oligoconjugated linoleic acid vesicles and the protective sustained release for curcumin in the gel

Assemblies of as called “chitosan hydrogel-liposome” are expected for overcoming the burst effect in drug release from chitosan (CS) hydrogels. Herein, a hydrogel delivery system made of chitosan incorporated fatty acid vesicles was constructed for protective sustained release of curcumin (Cur). The curcumin was encapsulated in the prepared oligo-conjugated linoleic acid vesicles (OCLAVs), and then the drug-embedded vesicles were constructed to Cur-OCLAVs-CS hydrogels with CS solution. The fabricated Cur-OCLAVs-CS hydrogel was fluidic at room temperature and could be rapidly gelled at 37 °C. Morphology study proves that the OCLAVs stayed as nano-vesicles in the gel. The Cur-OCLAVs-CS hydrogels effectively declined the burst effect with enhanced antioxidant activity. The Cur (400 μM)-OCLAVs-CS gel presented a cumulative release rate of 51.23 % of curcumin in 96 h, comparing to 93.37 % of that from the Cur-CS gel. Moreover, the corporation of OCLAVs and CS made the gel exhibited strong synergistic effect on the antioxidant activity, with an enhancement of up to 148.1 % on the ferric reducing power. Therefore, the hydrogel carrier made of incorporated fatty acid vesicles-chitosan can be served as an injectable or 3D printable drug delivery system, which may provide a hint to overcome the burst effect that existed in chitosan and other polysaccharide-based gels.

Investigation and Characterization of Factors Affecting Rheological Properties of Poloxamer-Based Thermo-Sensitive Hydrogel.

Poloxamers are negatively temperature-sensitive hydrogels and their hydrophilic groups interact with water molecules at lower temperatures (liquid phase) while their hydrophobic groups interact more strongly with increases in temperature causing gelation. To investigate the factors affecting the rheological properties of poloxamers, various parameters including different poloxamer P407 concentrations, poloxamers P407/P188 blending ratios and additives were examined. The results presented a clear trend of decreasing gelling temperature/time when P407 was at higher concentrations. Moreover, the addition of P188 enhanced the gelling temperature regardless of poloxamer concentration. Polysaccharides and their derivatives have been widely used as components of hydrogel and we found that alginic acid (AA) or carboxymethyl cellulose (CMC) reduced the gelling temperature of poloxamers. In addition, AA-containing poloxamer promoted cell proliferation and both AA -and CMC-containing poloxamer hydrogels reduced cell migration. This study investigated the intriguing characteristics of poloxamer-based hydrogel, providing useful information to compounding an ideal and desired thermo-sensitive hydrogel for further potential clinical applications such as development of sprayable anti-adhesive barrier, wound-healing dressings or injectable drug-delivery system for cartilage repair.

Development of nanosilver embedded injectable liquid crystalline hydrogel from alginate and chitosan for potent antibacterial and anticancer applications

Injectable hydrogels with macroscopic ordering have gained special attention in drug delivery due to their excellent biocompatibility and minimally invasive surgical procedure. Nanosilver embedded Schiff base hydrogel from biopolymers alginate and chitosan was developed and demonstrated its application in the injectable delivery of anticancer drug Dox.HCl. The ordered hydrogel structure was evidenced by FT-IR, DLS, XRD and Rheology. The self-assembled morphology of nanosilver- Schiff base hydrogels was studied by microscopic techniques such as SEM, TEM and AFM. The pH dependent anticancer activity of the hydrogel was demonstrated by invitro drug release studies at pH 5.5 and 86.56 % release was obtained for 100 mgL-1 of Dox.HCl loaded hydrogel at 72 hours. The antibacterial activity attained from nanosilver can be assessed by Agar well diffusion assay and minimum inhibitory concentration and minimum biocidal concentrations were determined as 62.5 μL/mL and 125 μL/mL, respectively. The invitro cell viability studies were done against skin cancer cell B16 by MTT assay which shows 34.82 % of toxicity towards B16 cancer cells and the cell death was further confirmed by Apoptosis assay and flow cytometry. The developed macroscopically ordered liquid crystalline hydrogel can be act as a versatile platform for injectable drug delivery system.

Fast Absorbent and Highly Bioorthogonal Hydrogels Developed by IEDDA Click Reaction for Drug Delivery Application.

In this work, we engineered highly biocompatible and fast absorbent injectable hydrogels derived from norbornene (Nb)-functionalized hyaluronic acid (HA-Nb) and a water-soluble cross-linker possessing tetrazine (Tz) functional groups on both ends of polyethylene glycol (PEG-DTz). The by-product (nitrogen gas) of the inverse electron demand Diels–Alder (IEDDA) cross-linking reaction carved porosity in the resulting hydrogels. By varying the molar ratio of HA-Nb and PEG-DTz (Nb:Tz = 10:10, 10:5, 10:2.5), we were able to formulate hydrogels with tunable porosity, gelation time, mechanical strength, and swelling ratios. The hydrogels formed quickly (gelation time < 100 s), offering a possibility to use them as an injectable drug delivery system. The experimental data showed rapid swelling and a high swelling ratio thanks to the existence of PEG chains and highly porous architectures of the hydrogels. The hydrogels were able to encapsulate a high amount of curcumin (~99%) and released the encapsulated curcumin in a temporal pattern. The PEG-DTz cross-linker, HA-Nb, and the resulting hydrogels showed no cytotoxicity in HEK-293 cells. These fast absorbent hydrogels with excellent biocompatibility fabricated from HA-Nb and the IEDDA click-able cross-linker could be promising drug carriers for injectable drug delivery applications.

Surface analysis of sequential semi-solvent vapor impact (SAVI) for studying microstructural arrangements of poly(lactide-co-glycolide) microparticles.

Biodegradable poly(lactide-co-glycolide) (PLGA) microparticles have been used as long-acting injectable (LAI) drug delivery systems for more than three decades. Despite extensive use, few tools have been available to examine and compare the three-dimensional (3D) structures of microparticles prepared using different compositions and processing parameters, all collectively affecting drug release kinetics. Surface analysis after sequential semi-solvent impact (SASSI) was conducted by exposing PLGA microparticles to different semi-solvent in the liquid phase. The use of semi-solvent liquids presented practical experimental difficulties, particularly in observing the same microparticles before and after exposure to semi-solvents. The difficulties were overcome by using a new sequential semi-solvent vapor (SSV) method to examine the morphological changes of the same microparticles. The SASSI method based on SSV is called surface analysis of semi-solvent vapor impact (SAVI). Semi-solvents are the solvents that dissolve PLGA polymers depending on the polymer's lactide:glycolide (L:G) ratio. A sequence of semi-solvents was used to dissolve portions of PLGA microparticles in an L:G ratio-dependent manner, thus revealing different structures depending on how microparticles were prepared. Exposing PLGA microparticles to semi-solvents in the vapor phase demonstrated significant advantages over using semi-solvents in the liquid phase, such as in control of exposure conditions, access to imaging, decreasing the time for sequential exposure of semi-solvents, and using the same microparticles. The SSV approach for morphological analysis provides another tool to enhance our understanding of the microstructural arrangement of PLGA polymers. It will improve our comprehensive understanding of the factors controlling drug release from LAI formulations based on PLGA polymers.

Micellization and gelation characteristics of Pluronic P123 and single ester-bonded cleavable cationic gemini surfactant: A potential system for solubilization and release of ibuprofen

We herein report the mixed micelle and monolayer formation of mixtures of a biocompatible and cleavable oxy-diester twin tailed (gemini) surfactant, 2,2′-[(oxybis(ethane-1,2-diyl))bis(oxy)]bis(N-hexadecyl-N,Ndimethyl-2-oxoethanaminium) dichloride (16-E1-16) with the triblock copolymer, P123 (HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H) using tensiometry, dynamic light scattering (DLS), and rheology. It was observed that P123 and 16-E1-16 have strong interaction and form small mixed micelles with similar micellar composition throughout the bulk mole fraction range with insignificant counterion binding. Besides, P123 and 16-E1-16 mixed surfactant system forms thermodynamically stable mixed monolayer that is rich in P123. Variation of viscosity with shear rate revealed better injectable property of the formulations of binary mixtures of P123 and 16-E1-16 compared to pure P123. Also, below α16-E1-16 = 0.3, all the mixtures were in the form of sol which transform into a weak gel at physiological temperatures making these formulations relevant as injectable delivery system. Solubilization capacity of these mixed micelles towards ibuprofen (IBU) showed that addition of 16-E1-16 to P123 micelles reduces its solubilization capacity but with the advantage of making the formulation injectable due to their favorable shear induced viscosity changes and thermogelation properties. Mixed micelles showed faster drug release rate predominantly following Fickian mechanism with negligible contribution of relaxation process in the release phenomena. There is no report showing interaction of biocompatible and cleavable gemini surfactant 16-E1-16 with P123 in mixed micelle and monolayer formation with detailed rheological, drug encapsulation and release studies even though this amphiphilic system has a potential to act as an injectable drug delivery system.

Synthesis and characterization of PnVCL grafted agar with potential temperature-sensitive delivery of Doxorubicin

Thermo-responsive copolymer, Agar agar-graft-poly(N-vinylcaproactam) (AA-g-PnVCL) was prepared by grafting N-vinylcaprolactam units onto the Agar backbone. Graft copolymer was synthesized by free-radical polymerization, using 2,2′-Azobis(2,4-dimethylvaleronitrile) (AMVN) as an initiator in the nitrogen atmosphere. In order to evaluate the composition effect different ratios between Agar agar, nVCL and AMVN were used. The formation of AA-g-PnVCL was confirmed by FT-IR, TGA, 1H NMR, and XRD techniques. Viscosity average molecular weight (Mη‾) was determined after the measurement of intrinsic viscosity. Turbidity measurements of dilute aqueous solutions were used to determine the lower critical solution temperature (LCST) of the new polymer. The grafting was evaluated by estimation of the percentage of grafting, grafting efficiency and percentage of conversion. One of the prepared polymer models (dried powder Model 4 with AA/VCL ratio 1:20 and VCL/AMVN ratio 20:1) showed the desired temperature-sensitive behavior (LCST 40 °C) and was further characterized. Its swelling was investigated with the determination of swelling indices in different media and at different temperatures. SEM images of dried and lyophilized gels were taken in order to investigate the morphology of the systems. Viscous and elastic moduli were determined at different temperatures for gel characterization. Doxorubicin (Dox) was chosen as a model drug and it was formulated into an injectable gel drug delivery system. Its loading and in vitro drug release was studied. The cytotoxicity of the proposed Dox loaded Model 4 was further characterized by the MTT test on H9c2 cardio blasts. The results showed successful preparation of a new temperature-sensitive polymer AA-g-PnVCL. Model 4 showed sufficient grafting efficiency and desired LCST for potential application as a modified drug delivery carrier. The proposed dosage form showed delayed release at 25° and 37 °C and rapid release at 40 °C. These results suggest that AA-g-PnVCL could be a potential stimuli-responsive material for controlled drug delivery in tumor chemotherapy with reduced cardiotoxicity of Doxorubicin.

Reduction-responsive and bioorthogonal carboxymethyl cellulose based soft hydrogels cross-linked via IEDDA click chemistry for cancer therapy application

In this work, novel biocompatible and reduction-responsive soft hydrogels were formulated from norbornene (Nb)-functionalized carboxymethyl cellulose (CMCNb). To cross-link the CMC-Nb via a highly bioorthogonal inverse electron demand Diels–Alder (IEDDA) reaction, we employed a water-soluble and reduction-responsive diselenide-based cross-linker possessing two terminal tetrazine (Tz) groups with varying molar concentrations (Nb/Tz molar ratios of 10/10, 10/05, and 10/2.5). The N2 microbubbles liberated as a by-product during the IEDDA reaction generated in-situ pores in hydrogel networks. The resulting hydrogels had highly porous structures and relatively soft mechanical properties (storage moduli in the range 74 ⁓160 Pa). The hydrogels showed high swelling ratios (>35 times), tunable gelation times (1–5 min), and excellent doxorubicin (DOX) loading efficiencies (>85 %). The hydrogels exhibited stimuli-responsive and fast release of DOX (99 %, after 12 h) in the presence of 10 mmol of glutathione as compared to the normal PBS solution (38 %). The cytotoxic effects of blank hydrogels were not observed against HEK-239 cells, while the DOX-encapsulated hydrogels exhibited anti-tumor activity in BT-20 cancer cells. The results indicate potential applications of the CMC-based soft hydrogels in injectable drug delivery systems.

Photocrosslinkable methacrylated gelatin hydrogel as a cell-friendly injectable delivery system for chlorhexidine in regenerative endodontics

ObjectivesThis work sought to formulate photocrosslinkable chlorhexidine (CHX)-laden methacrylated gelatin (CHX/GelMA) hydrogels with broad spectrum of action against endodontic pathogens as a clinically viable cell-friendly disinfection therapy prior to regenerative endodontics procedures. MethodsCHX/GelMA hydrogel formulations were successfully synthesized using CHX concentrations between 0.12 % and 5 % w/v. Hydrogel microstructure was evaluated by scanning electron microscopy (SEM). Swelling and enzymatic degradation were assessed to determine microenvironmental effects. Compression test was performed to investigate the influence of CHX incorporation on the hydrogels’ biomechanics. The antimicrobial and anti-biofilm potential of the formulated hydrogels were assessed using agar diffusion assays and a microcosms biofilm model, respectively. The cytocompatibility was evaluated by exposing stem cells from human exfoliated deciduous teeth (SHEDs) to hydrogel extracts (i.e., leachable byproducts obtained from overtime hydrogel incubation in phosphate buffer saline). The data were analyzed using One- and Two-way ANOVA and Tukey’s test (α = 0.05). ResultsCHX/GelMA hydrogels were effectively prepared. NMR spectroscopy confirmed the incorporation of CHX into GelMA. The addition of CHX did not change the micromorphology (pore size) nor the swelling profile (p > 0.05). CHX incorporation reduced the degradation rate of the hydrogels (p < 0.001); whereas, it contributed to increased compressive modulus (p < 0.05). Regarding the antimicrobial properties, the incorporation of CHX showed a statistically significant decrease in the number of bacteria colonies at 0.12 % and 0.5 % concentration (p < 0.001) and completely inhibited the growth of biofilm at concentration levels 1 %, 2 %, and 5 %. Meanwhile, the addition of CHX, regardless of the concentration, did not lead to cell toxicity, as cell viability values were above 70 %. SignificanceThe addition of CHX into GelMA showed significant antimicrobial action against the pathogens tested, even at low concentrations, with the potential to be used as a cell-friendly injectable drug delivery system for root canal disinfection prior to regenerative endodontics.

The effect of PEO homopolymers on the behaviours and structural evolution of Pluronic F127 smart hydrogels for controlled drug delivery systems

Understanding the structure-property relationships of drug delivery system (DDS) components is critical for their development and the prediction of bodily performance. This study investigates the effects of introducing polyethylene oxide (PEO) homopolymers, over a wide range of molecular weights, into Pluronic injectable smart hydrogel formulations. These smart DDSs promise to enhance patient compliance, reduce adverse effects and dosing frequency. Pharmaceutically, Pluronic systems are attractive due to their unique sol-gel phase transition in the body, biocompatibility, safety and ease of injectability as solutions before transforming into gel matrices at body temperature. This paper presents a systematic and comprehensive evaluation of gelation and the interplay of microscopic and macroscopic properties under both equilibrium and non-equilibrium conditions in controlled environments, as measured by rheology in conjunction with time-resolved Small Angle Neutron Scattering (SANS). The non-equilibrium conditions investigated in this work offer a better understanding of the two polymeric systems’ complex interactions affecting the matrix thermo-rheological behaviour and structure and therefore the future release of an active pharmaceutical ingredient from the injectable DDS.

In situ injectable hydrogel-loaded drugs induce anti-tumor immune responses in melanoma immunochemotherapy.

Melanoma is a highly aggressive tumor located in the skin, with limited traditional therapies. In order to reduce the side effects caused by traditional administration method and amplify the killing effect of immune system against tumor cells, an in situ injectable hydrogel drug delivery system is developed for the first time which co-delivers doxorubicin (Dox) and imiquimod (R837) for the synergistic therapy of melanoma. The mechanical properties and stability of the hydrogel are characterized and the optimal doses of hydrogel and drugs are also identified. As a result, the co-delivery system effectively suppresses melanoma growth and metastatic progression both in vitro and in vivo. Further studies show that the co-delivery system causes immunogenic cell death, activation of antigen presenting cells, comprising dendritic cells and M1 macrophages, and secretion of related cytokines consisted of tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), subsequently with the activation of T lymphocytes and natural killer cells in spleen and tumor area. The co-delivery system also decreases the suppressive immune responses, including infiltration of M2 macrophages and secretion of interleukin-10 (IL-10), in vivo. Besides, other death modes are induced by the co-delivery system, including apoptosis and non-apoptotic cell death. In a word, this co-delivery system induces melanoma cell death directly and activates immune system for further tumor killing simultaneously, which shows probability for precise targeted tumor therapy.

Injectable hydrogels with high drug loading through B–N coordination and ROS-triggered drug release for efficient treatment of chronic periodontitis in diabetic rats

The clinical management of chronic periodontitis with diabetes mellitus (CPDM) is a long-standing thorny issue. The excessive production of reactive oxygen species (ROS) is one of the important implications in CPDM. In the present study, oxidized dextran (OD) and phenylboronic acid-functionalized poly (ethylene imine) (PBA-PEI) were used to develop a novel injectable local drug delivery system (LDDS) which could simultaneously improve drug loading efficiency (doxycycline (Doxy) and metformin (Met)) through B–N coordination and achieve ROS-triggered drug release locally. The injectable LDDS exhibited appropriate adhesiveness to gingival tissue, good biocompatibility, and remarkable antibacterial effect against S. aureus, E. coli, and P. gingivalis. Furthermore, the favorable synergistic effect of Doxy and Met was also verified in vivo in a CPDM rat model through the morphometry and histological observations of alveolar bone, immunohistochemistry staining, and the detection of the expression level of immune-inflammatory mediators in gingival tissue. The results show that the double drug-loaded PBA-PEI/OD hydrogel, as a novel promising therapeutic agent, may be a favorable potential candidate for the CPDM management in the dental clinic.

High-yield halide-assisted synthesis of metal–organic framework UiO-based nanocarriers

The synthesis of nanosized metal–organic frameworks (NMOFs) is requisite for their application as injectable drug delivery systems (DDSs) and other biorelevant purposes. Herein, we have critically examined the role of different synthetic parameters leading to the production of UiO-66 crystals smaller than 100 nm. Of note, we demonstrate the co-modulator role conferred by halide ions, not only to produce NMOFs with precise morphology and size, but also to significantly improve the reaction yield. The resulting NMOFs are highly crystalline and exhibit sustained colloidal stability in different biologically relevant media. As a proof of concept, these NMOFs were loaded with Rhodamine 6G (R6G), which remained trapped in most common biologically relevant media. When incubated with living mammalian cells, the R6G-loaded NMOFs were efficiently internalized and did not impair cell viability even at relatively high doses.

Resveratrol‐Loaded Poly(d,l‐Lactide‐Co‐Glycolide) Microspheres Integrated in a Hyaluronic Acid Injectable Hydrogel for Cartilage Regeneration

Cartilage tissue has a relatively low regenerative capacity which leads to a need for disease‐modifying active pharmaceutical ingredients (APIs) which can stimulate its regeneration and more urgently, effective ways of introducing APIs into the cartilage defects. Herein, an integrated system is proposed in which a hyaluronic acid (HA)‐based injectable hydrogel scaffold is embedded with API‐loaded poly(d,l‐lactide‐co‐glycolide) microspheres (PLGA MPs). This new injectable drug delivery system can successfully deliver APIs locally, increase drug retention time, and promote endogenous cartilage regeneration. In this study, resveratrol (RSV), a small hydrophobic compound is introduced as the selected API. PLGAs with differing copolymer ratios and endgroups are evaluated to study their effects on particle formation, RSV encapsulation, and drug release kinetics. This system is optimized as a 1 month sustained release formulation. In addition, the long‐acting chondrogenic induction of the RSV‐loaded system is evaluated by coculturing with cartilage‐derived progenitor cells in vitro. PLGA–RSV MPs stimulated the expression of cartilage‐related genes and the production of the cartilage‐specific extracellular matrix. This integrated system shows great potential as an injectable formulation for long‐acting chondrogenesis and endogenous cartilage tissue regeneration.

Thermosensitive collagen/fibrinogen gels loaded with decorin suppress lesion site cavitation and promote functional recovery after spinal cord injury

The treatment of spinal cord injury (SCI) is a complex challenge in regenerative medicine, complicated by the low intrinsic capacity of CNS neurons to regenerate their axons and the heterogeneity in size, shape and extent of human injuries. For example, some contusion injuries do not compromise the dura mater and in such cases implantation of preformed scaffolds or drug delivery systems may cause further damage. Injectable in situ thermosensitive scaffolds are therefore a less invasive alternative. In this study, we report the development of a novel, flowable, thermosensitive, injectable drug delivery system comprising bovine collagen (BC) and fibrinogen (FB) that forms a solid BC/FB gel (Gel) immediately upon exposure to physiological conditions and can be used to deliver reparative drugs, such as the naturally occurring anti-inflammatory, anti-scarring agent Decorin, into adult rat spinal cord lesion sites. In dorsal column lesions of adult rats treated with the Gel + Decorin, cavitation was completely suppressed and instead lesion sites became filled with injury-responsive cells and extracellular matrix materials, including collagen and laminin. Decorin increased the intrinsic potential of dorsal root ganglion neurons (DRGN) by increasing their expression of regeneration associated genes (RAGs), enhanced local axon regeneration/sprouting, as evidenced both histologically and by improved electrophysiological, locomotor and sensory function recovery. These results suggest that this drug formulated, injectable hydrogel has the potential to be further studied and translated into the clinic.

Injectable Multifunctional Drug Delivery System for Hard Tissue Regeneration under Inflammatory Microenvironments.

Engineering multifunctional hydrogel systems capable of amplifying the regenerative capacity of endogenous progenitor cells via localized presentation of therapeutics under tissue inflammation is central to the translation of effective strategies for hard tissue regeneration. Here, we loaded dexamethasone (DEX), a pleotropic drug with anti-inflammatory and mineralizing abilities, into aluminosilicate clay nanotubes (halloysite clay nanotubes (HNTs)) to engineer an injectable multifunctional drug delivery system based on photo-cross-linkable gelatin methacryloyl (GelMA) hydrogel. In detail, a series of hydrogels based on GelMA formulations containing distinct amounts of DEX-loaded nanotubes was analyzed for physicochemical and mechanical properties and kinetics of DEX release as well as compatibility with mesenchymal stem cells from human exfoliated deciduous teeth (SHEDs). The anti-inflammatory response and mineralization potential of the engineered hydrogels were determined in vitro and in vivo. DEX conjugation with HNTs was confirmed by FTIR analysis. The incorporation of DEX-loaded nanotubes enhanced the mechanical strength of GelMA with no effect on its degradation and swelling ratio. Scanning electron microscopy (SEM) images demonstrated the porous architecture of GelMA, which was not significantly altered by DEX-loaded nanotubes' (HNTs/DEX) incorporation. All GelMA formulations showed cytocompatibility with SHEDs (p < 0.05) regardless of the presence of HNTs or HNTs/DEX. However, the highest osteogenic cell differentiation was noticed with the addition of HNT/DEX 10% in GelMA formulations (p < 0.01). The controlled release of DEX over 7 days restored the expression of alkaline phosphatase and mineralization (p < 0.0001) in lipopolysaccharide (LPS)-stimulated SHEDs in vitro. Importantly, in vivo data revealed that DEX-loaded nanotube-modified GelMA (5.0% HNT/DEX 10%) led to enhanced bone formation after 6 weeks (p < 0.0001) compared to DEX-free formulations with a minimum localized inflammatory response after 7 days. Altogether, our findings show that the engineered DEX-loaded nanotube-modified hydrogel may possess great potential to trigger in situ mineralized tissue regeneration under inflammatory conditions.

Using rheology to quantify the effects of localized collagenase treatments on uterine fibroid digestion

Uterine fibroids are stiff, benign tumors containing excessive, disordered collagens that occur in 70-80% of women before age 50 and cause bleeding and pain. Collagenase Clostridium histolyticum (CCH) is a bacterial enzyme capable of digesting the collagens present in fibroids. By combining CCH with injectable drug delivery systems to enhance effectiveness, a new class of treatments could be developed to reduce the stiffness of fibroids, preventing the need for surgical removal and preserving fertility. In this work, we achieved localization of CCH via physical entrapment by co-injecting a thermoresponsive pNIPAM-based polymeric delivery system called LiquoGel (LQG), which undergoes a sol-gel transition upon heating. Toxicity study results for LQG injected subcutaneously into mice demonstrate that LQG does not induce lesions or other adverse effects. We then used rheology to quantify the effects of localized CCH injections on the modulus and viscoelasticity of uterine fibroids, which exhibit gel-like behavior, through ex vivo and in vivo digestion studies. Ex vivo CCH injections reduce the tissue modulus by over two orders of magnitude and co-injection of LQG enhances this effect. Rheological results from an in vivo digestion study in mice show a significant reduction in tissue modulus and increase in tissue viscoelasticity 7 days after a single injection of LQG+CCH. Parallel histological staining validates that the observed rheological changes correspond to an increase in collagen lysis after treatment by LQG+CCH. These results show promise for development of injectable and localized enzymatic therapies for uterine fibroids and other dense tumors. Statement of significanceUterine fibroids are stiff, benign tumors containing high collagen levels that cause bleeding and pain in women. Fertility-preserving and minimally-invasive treatments to soften fibroids are needed as an alternative to surgical removal via hysterectomy. We demonstrate through ex vivo and in vivo studies that co-injecting a thermoresponsive polymer delivery system (LQG) alongside a bacterial collagenase (CCH) enzyme significantly increases treatment effectiveness at softening fibroids through CCH localization. We use rheology to measure the modulus and viscoelasticity of fibroids and histology to show that fibroid softening corresponds to a decrease in collagen after treatment with LQG+CCH. These results highlight the utility of rheology at quantifying tissue properties and present a promising injectable therapy for fibroids and other dense tumors.

Chitosan–dipeptide hydrogels as potential anticancer drug delivery systems

A novel chitosan–dipeptide hydrogel was fabricated through a combination of self-assembly of 9-fluorenylmethoxycarbonyl-modified diphenylalanine (Fmoc–FF) and its electrostatic interaction with glycol chitosan (GCS). Hydrogel strength and stability depended on its composition. The highest gel strength was observed at a Fmoc–FF mass fraction (ϕFF) of 0.85, whereby the highest combined strength of the two interactions was achieved. As the ϕFF increased above 0.6, gel stability decreased in buffered solution at pH 7.46. The incorporation of doxorubicin (DOX) as a cationic model drug significantly increased the stability of the complex hydrogels. DOX-loaded hydrogels exhibited slow DOX release, probably due to the drug's strong binding to Fmoc–FF via electrostatic attraction and the high gel stability. These hydrogels also exhibited excellent thixotropic features that facilitated the development of injectable self-healing drug delivery systems. Notably, DOX release was significantly accelerated as the pH of the medium decreased from 7.46 to 5.5 and 4.0, possibly due to hydrogel components' protonation. The DOX-loaded hydrogel exhibited notable cytotoxicity against A549 human lung cancer cells, which suggests the newly developed hydrogel to be a promising candidate vehicle for the localized and controlled drug delivery in cancer therapy.

Preparation and characterization of injectable self-antibacterial gelatin/carrageenan/bacterial cellulose hydrogel scaffolds for wound healing application

This study reports the preparation of self-crosslinked Schiff base gels using gelatin and oxidized carrageenan gum interpenetrated with bacterial cellulose (BC) as injectable drug delivery systems. The injectable gels were successfully prepared at body temperature upon blending with BC and loaded with bovine serum albumin (as the model drug) to produce scaffolds. The gel scaffolds were characterized via rheological, FTIR, SEM, XRD, TGA and mechanical compression analysis. Gelation kinetics of gels as well as swelling, in vitro degradation and drug release kinetics of gel scaffolds were examined. Results showed that the incorporation of BC to the gel system considerably improved mechanical integrity with remarkable rheological shear-thinning properties. Maximum in vitro cumulative drug release from gel scaffolds was determined as 84.01 ± 3.66% within the studied time interval of 168 h. Further analysis showed that the prepared gel scaffolds possess self-antibacterial properties with growth inhibition capacity against E. coli, S. aureus, and K. pneumonia. In vitro cell cytotoxicity was also performed by MTT assay and results depicted >80% cell viability, which indicates the gel scaffolds are cytocompatible. In conclusion, this paper presents a facile approach to fabricate all-natural crosslinked injectable self-antibacterial gels systems with prospective potential application in wound dressing and tissue regeneration.