Dual Delivery Research Articles

Glycol chitosan/oxidized hyaluronic acid hydrogel film for topical ocular delivery of dexamethasone and levofloxacin

In the present study, we fabricated a glycol chitosan/oxidized hyaluronic acid hydrogel film with promising potential for the dual ophthalmic delivery of dexamethasone (Dex) and levofloxacin (Lev). Utilizing different oxidation degrees of oxidized hyaluronic acid (OHA), several blank hydrogel films and Lev-loaded hydrogel films were successfully fabricated. With an increase in the oxidation degree of OHA, the swelling ratio of the hydrogel films decreased accordingly. The hydrogel films displayed a stepwise release of Lev and Dex, with Lev rapidly released from the hydrogel film, followed by a sustained release of Dex. Lev-loaded hydrogel films revealed a potent capacity to inhibit bacterial growth in different bacterial strains. In lipopolysaccharide-activated RAW264.7 macrophages, the formulated hydrogel films displayed potent in vitro anti-inflammatory activity by significantly downregulating various inflammatory cytokines. Overall, the fabricated hydrogel film acting as a dual drug delivery system might be a promising vehicle for the treatment of postoperative endophthalmitis.

Dual delivery of IL-10 and AT-RvD1 from PEG hydrogels polarize immune cells towards pro-regenerative phenotypes

Inflammation after traumatic injury or surgical intervention is both a protective tissue response leading to regeneration and a potential cause of wound complications. One potentially successful strategy to harness to pro-regenerative roles of host inflammation is the localized delivery of bioactive materials to induce immune suppressive cellular responses by cells responding to injury. In this study, we designed a fully synthetic poly (ethylene) glycol (PEG)-based hydrogel to release the specialized pro-resolving lipid mediator aspirin-triggered resolvin-D1 (AT-RvD1) and recombinant human interleukin 10 (IL-10). We utilized a unique side-by-side internally controlled implant design wherein bioactive hydrogels were implanted adjacent to control hydrogels devoid of immune modulatory factors in the dorsal skinfold window chamber. We also explored single-immune cell data with unsupervised approaches such as SPADE. First, we show that RGD-presenting hydrogel delivery results in enhanced immune cell recruitment to the site of injury. We then use intra-vital imaging to assess cellular recruitment and microvascular remodeling to show an increase in the caliber and density of local microvessels. Finally, we show that the recruitment and re-education of mononuclear phagocytes by combined delivery IL-10 and AT-RvD1 localizes immune suppressive subsets to the hydrogel, including CD206+ macrophages (M2a/c) and IL-10 expressing dendritic cells in the context of chronic inflammation following surgical tissue disruption. These data demonstrate the potential of combined delivery on the recruitment of regenerative cell subsets involved in wound healing complications.

Pancreatic cancer-targeting exosomes for enhancing immunotherapy and reprogramming tumor microenvironment

Immunotherapy has gained increasing focus in treating pancreatic ductal adenocarcinoma (PDAC), since conventional therapies like chemotherapy could not provide satisfactory improvement in overall survival outcome of PDAC patients. However, it is still not the game changing solution due to the unique tumor microenvironment and low cancer immunogenicity of PDAC. Thus, inducing more intratumoral effector immune cells as well as reversing immunosuppression is the core of PDAC treatment. Herein, we demonstrate an exosome-based dual delivery biosystem for enhancing PDAC immunotherapy as well as reversing tumor immunosuppression of M2-like tumor associated macrophages (M2-TAMs) upon disruption of galectin-9/dectin 1 axis. The deliver system is constructed from bone marrow mesenchymal stem cell (BM-MSC) exosomes, electroporation-loaded galectin-9 siRNA, and surficially modified with oxaliplatin (OXA) prodrug as an immunogenic cell death (ICD)-trigger. The use of biomaterials, BM-MSC exosomes, can significantly improve tumor targeting efficacy, thus increasing drug accumulation in the tumor site. The combined therapy (iEXO-OXA) elicits anti-tumor immunity through tumor-suppressive macrophage polarization, cytotoxic T lymphocytes recruitment and Tregs downregulation, and achieves significant therapeutic efficacy in cancer treatment.

Single and Dual Vector Gene Therapy with AAV9-PHP.B Rescues Hearing in Tmc1 Mutant Mice

AAV-mediated gene therapy is a promising approach for treating genetic hearing loss. Replacement or editing of the Tmc1 gene, encoding hair cell mechanosensory ion channels, is effective for hearing restoration in mice with some limitations. Efficient rescue of outer hair cell function and lack of hearing recovery with later-stage treatment remain issues to be solved. Exogenous genes delivered with the adeno-associated virus (AAV)9-PHP.B capsid via the utricle transduce both inner and outer hair cells of the mouse cochlea with high efficacy. Here, we demonstrate that AAV9-PHP.B gene therapy can promote hair cell survival and successfully rescues hearing in three distinct mouse models of hearing loss. Tmc1 replacement with AAV9-PHP.B in a Tmc1 knockout mouse rescues hearing and promotes hair cell survival with equal efficacy in inner and outer hair cells. The same treatment in a recessive Tmc1 hearing-loss model, Baringo, partially recovers hearing even with later-stage treatment. Finally, dual delivery of Streptococcus pyogenes Cas9 (SpCas9) and guide RNA (gRNA) in separate AAV9-PHP.B vectors selectively disrupts a dominant Tmc1 allele and preserves hearing in Beethoven mice, a model of dominant, progressive hearing loss. Tmc1-targeted gene therapies using single or dual AAV9-PHP.B vectors offer potent and versatile approaches for treating dominant and recessive deafness.

Dual self-regulated delivery of insulin and glucagon by a hybrid patch

Reduced β-cell function and insulin deficiency are hallmarks of diabetes mellitus, which is often accompanied by the malfunction of glucagon-secreting α-cells. While insulin therapy has been developed to treat insulin deficiency, the on-demand supplementation of glucagon for acute hypoglycemia treatment remains inadequate. Here, we describe a transdermal patch that mimics the inherent counterregulatory effects of β-cells and α-cells for blood glucose management by dynamically releasing insulin or glucagon. The two modules share a copolymerized matrix but comprise different ratios of the key monomers to be "dually responsive" to both hyper- and hypoglycemic conditions. In a type 1 diabetic mouse model, the hybrid patch effectively controls hyperglycemia while minimizing the occurrence of hypoglycemia in the setting of insulin therapy with simulated delayed meal or insulin overdose.

Glycyrrhetinic Acid-Functionalized Mesoporous Silica Nanoparticles for the Co-Delivery of DOX/CPT-PEG for Targeting HepG2 Cells.

A pH-triggered mesoporous silica nanoparticle (MSN)-based nano-vehicle for the dual delivery of doxorubicin (DOX)/camptothecin-PEG (CPT-PEG) has been prepared. To enhance its selectivity, the nanoparticles were decorated with glycyrrhetinic acid (GA) to target HepG2 cells. The highly insoluble CPT was derivatized with a reductive-cleavable PEG chain to improve its loading within the MSN. The preparation of these particles consisted of four steps. First, CPT-PEG was loaded within the pores of the MSN. Then, dihydrazide polyethylene glycol chains were introduced onto the surface of an aldehyde-functionalized MSN by means of a hydrazone bond. Afterwards, DOX was covalently attached to the other end of the dihydrazide polyethylene glycol chains. Finally, the resulting nanoparticles were decorated with GA by formation of an imine bond between the amino group of DOX and a benzaldehyde-GA derivative. The system was stable at physiological conditions and the release of both drugs was negligible. However, at acidic pH, a burst release of DOX and a gradual release of CPT-PEG takes place. GA-decorated drug delivery systems (DDS) selectively internalizes into HepG2. In vitro tests demonstrated that this system shows a great cytotoxicity towards HepG2 cells. Furthermore, glutathione cleavage of CPT prodrug assures the formation of free CPT leading to a synergistic effect in combination with DOX.

Single-Step Fabrication of Core–Shell Microgels for the Controlled Release of rhBMP-2 and Simvastatin to Induce Osteogenesis

Dual delivery of bioactive molecules (drugs and growth factors) has been attempted to enhance multiple processes during tissue regeneration. For bone tissue engineering, many attempts have been mad...

New insights into Hexakis macrocycles as a novel nano-carrier for highly potent anti-cancer treatment: A new challenge in drug delivery

The purpose of this study is to design and evaluate a new tubular assembly structure of Hexakis (m-phenylene ethynylene) (m-PE) macrocycles and to explore its potential application as an innovative drug delivery system. First, we focused on how (m-PE) macrocycles can be self-assembled in both chloroform (CHCl3) and water solvents for the formation of the assembled nanotube using molecular dynamics (MD) simulations. In contrast to their behavior in water solvent, all ten (m-PE) macrocycles remain aggregated at low concentrations of CHCl3. We found that these macrocycles carrying chiral side chains and capable of H-bonded self-association, assemble into tubular stacks. Then, the dual delivery strategy for the transport of doxorubicin (DOX) and curcumin (Cur) on the self-assembly system of hexakis (m-PE) nanocarrier is examined using molecular dynamics (MD) simulation and free energy calculation. The obtained results indicated that the binding energy of DOX (− 298.9 kJ/mol) on hexakis (m-PE) in the presence of Cur is higher than free DOX (− 247.7 kJ/mol). Furthermore, in the interaction of the DOX and hexakis m-PE, the contribution of van der Walls (vdW) energy is higher than electrostatic (elec) energy, which can be related to the strong π-π interactions between the drug molecules with the carrier surface. In general, the results indicated that the simultaneous delivery of DOX and Cur through DOX/Cur/hexakis (m-PE) could be a promising vehicle in tumor therapy. Based on the obtained results of the present research, hexakis (m-PE) macrocycle can be used as a drug delivery vehicle for targeted or systemic delivery.

Dual Gene Delivery Reagents From Antiproliferative Alkylphospholipids for Combined Antitumor Therapy.

Alkylphospholipids (APLs) have elicited great interest as antitumor agents due to their unique mode of action on cell membranes. However, their clinical applications have been limited so far by high hemolytic activity. Recently, cationic prodrugs of erufosine, a most promising APL, have been shown to mediate efficient intracellular gene delivery, while preserving the antiproliferative properties of the parent APL. Here, cationic prodrugs of the two APLs that are currently used in the clinic, miltefosine, and perifosine, are investigated and compared to the erufosine prodrugs. Their synthesis, stability, gene delivery and self-assembly properties, and hemolytic activity are discussed in detail. Finally, the potential of the pro-miltefosine and pro-perifosine compounds ME12 and PE12 in combined antitumor therapy is demonstrated using pUNO1-hTRAIL, a plasmid DNA encoding TRAIL, a member of the TNF superfamily. With these pro-APL compounds, we provide a proof of concept for a new promising strategy for cancer therapy combining gene therapy and APL-based chemotherapy.

Dual Delivery of Gemcitabine and Paclitaxel by Wet‐Spun Coaxial Fibers Induces Pancreatic Ductal Adenocarcinoma Cell Death, Reduces Tumor Volume, and Sensitizes Cells to Radiation

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis, with surgical resection of the tumor in conjunction with systemic chemotherapy the only potential curative therapy. Up to 80% of diagnosed cases are deemed unresectable, prompting the need for alternative treatment approaches. Herein, coaxial polymeric fibers loaded with two chemotherapeutic agents, gemcitabine (Gem) and paclitaxel (Ptx), are fabricated to investigate the effect of local drug delivery on PDAC cell growth in vitro and in vivo. A wet-spinning fabrication method to form a coaxial fiber with a polycaprolactone shell and alginate core loaded with Ptx and Gem, respectively, is used. In vitro, Gem+Ptx fibers display significant cytotoxicity as well as radiosensitizing properties toward PDAC cell lines greater than the equivalent free drugs, which may be attributed to a radiosensitizing effect of the polymers. In vivo studies assessing Gem+Ptx fiber efficacy found that Gem+Ptx fibers reduce tumor volume in a xenograft mouse model of PDAC. Importantly, no difference in mouse weight, circulating cytokines, or liver function is observed in mice treated with Gem+Ptx fibers compared to the empty fiber controls confirming the safety of the implant approach. With further development, Gem+Ptx fibers can improve the treatment of unresectable PDAC in the future.

Synergetic therapy of glioma mediated by a dual delivery system loading \u03b1-mangostin and doxorubicin through cell cycle arrest and apoptotic pathways

Two of the biggest hurdles in the deployment of chemotherapeutics against glioma is a poor drug concentration at the tumor site and serious side effects to normal tissues. Nanocarriers delivering different drugs are considered to be one of the most promising alternatives. In this study, a dual delivery system (methoxy poly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL)) loaded with α-mangostin (α-m) and doxorubicin (Dox) was decorated and constructed by self-assembly to determine its ability to treat glioma. Molecular dynamics simulations showed that MPEG-PCL could provide ideal interaction positions for both α-m and Dox, indicating that the two drugs could be loaded into MPEG-PCL. Based on the in vitro results, MPEG-PCL loaded with α-m and Dox (α-m-Dox/M) with a size of 25.68 nm and a potential of −1.51 mV was demonstrated to significantly inhibit the growth and promote apoptosis in Gl261, C6 and U87 cells, and the effects of the combination were better than each compound alone. The mechanisms involved in the suppression of glioma cell growth were blockage of the cell cycle in S phase by inhibition of CDK2/cyclin E1 and promotion of apoptosis through the Bcl-2/Bax pathway. The synergetic effects of α-m-Dox/M effectively inhibited tumor growth and prolonged survival time without toxicity in mouse glioma models by inducing glioma apoptosis, inhibiting glioma proliferation and limiting tumor angiogenesis. In conclusion, a codelivery system was synthesized to deliver α-m and Dox to the glioma, thereby suppressing the development of glioma by the mechanisms of cell cycle arrest and cellular apoptosis, which demonstrated the potential of this system to improve the chemotherapy response of glioma.

Comparison of CRISPR/Cas Endonucleases for in vivo Retinal Gene Editing.

CRISPR/Cas has opened the prospect of direct gene correction therapy for some inherited retinal diseases. Previous work has demonstrated the utility of adeno-associated virus (AAV) mediated delivery to retinal cells in vivo; however, with the expanding repertoire of CRISPR/Cas endonucleases, it is not clear which of these are most efficacious for retinal editing in vivo. We sought to compare CRISPR/Cas endonuclease activity using both single and dual AAV delivery strategies for gene editing in retinal cells. Plasmids of a dual vector system with SpCas9, SaCas9, Cas12a, CjCas9 and a sgRNA targeting YFP, as well as a single vector system with SaCas9/YFP sgRNA were generated and validated in YFP-expressing HEK293A cell by flow cytometry and the T7E1 assay. Paired CRISPR/Cas endonuclease and its best performing sgRNA was then packaged into an AAV2 capsid derivative, AAV7m8, and injected intravitreally into CMV-Cre:Rosa26-YFP mice. SpCas9 and Cas12a achieved better knockout efficiency than SaCas9 and CjCas9. Moreover, no significant difference in YFP gene editing was found between single and dual CRISPR/SaCas9 vector systems. With a marked reduction of YFP-positive retinal cells, AAV7m8 delivered SpCas9 was found to have the highest knockout efficacy among all investigated endonucleases. We demonstrate that the AAV7m8-mediated delivery of CRISPR/SpCas9 construct achieves the most efficient gene modification in neurosensory retinal cells in vivo.

A Dual Nanoparticle Delivery Strategy for Enhancing Drug Distribution in Cancerous Tissue.

Nanoparticle-mediated drug delivery may be a promising alternative to traditional chemotherapy of high systemic toxicity. Tumor tissue architecture poses a challenge to delivery of nanoparticles. Small and spherical nanoparticles have poor adherence to the tumor vasculature, while larger and more eccentric ones create high heterogeneity in tissue-to-drug exposure. In previous work, we quantified these tradeoffs using numerical optimization. In this study, we demonstrate that simultaneous delivery of multiple nanoparticle designs can enhance drug distribution in the cancerous tissue without compromising nanoparticle tumoral accumulation. We formulate and solve optimization problems to find the optimal constituent of the heterogeneous injection in terms of nanoparticle design diversity that increases drug distribution by 14%.

Changing language mindsets about modern languages: a school intervention

ABSTRACT In the context of the UK language learning crisis, several studies have aimed to influence student attitude towards languages via school interventions, with mixed results. A six-session tacking diverse metalinguistic issues (e.g. cognitive benefits of language learning, world languages) was carried out in three secondary schools in England, using both whole-class and small-group teaching. The study included a hitherto unmet aim, that of changing mindsets in mixed-ability settings, including students with the most negative language mindsets. Pre-post differences reveal that beliefs about language learning improved more than self-efficacy. Inclination to continue modern foreign language (MFL) study improved more in those students initially most disinclined to continue. Given the well-known gender divide in MFL uptake, it was pleasing to note that the intervention showed greater effect on boys than girls. Qualitative and quantitative data suggest that the intervention might have had a small ‘equalising’ effect in gender differences, in that boys’ self-efficacy improved more than girls’. The study concludes that the dual delivery (whole-class teaching and in-school mentoring, delivered by older students in the same school) offers a promising format, but that, in order to achieve greater effects, more contact time and more mentor preparation are needed.

Development of PLGA-PEG-COOH and gelatin-based microparticles dual delivery system and E-beam sterilization effects for controlled release of BMP-2 and IGF-1.

The purpose of this study was to develop a PLGA-PEG-COOH- and gelatin-based microparticles (MPs) dual delivery system for release of BMP-2 and IGF-1. We made and characterized the delivery system based on its morphology, loading capacity, Encapsulation efficiency and release kinetics. Second, we examined the effects of electron beam (EB) sterilization on BMP-2 and IGF-1 loaded MPs and their biological effects. Third, we evaluated the synergistic effect of a controlled dual release of BMP-2 and IGF-1 on osteogenesis of MSCs. Encapsulation efficiency of growth factors into gelatin and PLGA-PEG-COOH MPs are in the range of 64.78% to 76.11%. E-beam sterilized growth factor delivery systems were effective in significantly promoting osteogenesis of MSCs, although E-beam sterilization decreased the bioactivity of growth factors in MPs by approximately 22%. BMP-2 release behavior from gelatin MPs/PEG hydrogel shows a faster release (52.7%) than that of IGF-1 from the PLGA-PEG-COOH MPs/PEG hydrogel (27.3%). The results demonstrate that the gelatin and PLGA-PEG-COOH MPs based delivery system could realize temporal release of therapeutic biomolecules by incorporating different growth factors into distinct microparticles. EB sterilization was an accessible method for sterilizing growth factors loaded carriers, which could pave the way for implementing growth factor delivery in clinical applications.

Combined Delivery of Two Different Bioactive Factors Incorporated in Hydroxyapatite Microcarrier for Bone Regeneration.

The delivery of growth factors using a carrier system presents a promising and innovative tool in tissue engineering and dentistry today. Two of the foremost bioactive factors, bone morphogenetic protein-2 and vascular endothelial growth factor (VEGF), are widely applied using a ceramic scaffold. The aim of this study was to determine the use of hydroxyapatite microcarrier (MC) for dual delivery of osteogenic and angiogenic factors to accelerate hard tissue regeneration during the regenerative process. Two MCs of different sizes were fabricated by emulsification of gelatin and alpha-tricalcium phosphate (α-TCP). The experimental group was divided based on the combination of MC size and growth factors. For investigating the in vitro properties, rat mesenchymal stem cells (rMSCs) were harvested from bone marrow of the femur and tibia. For in vivo experiments, MC with/without growth factors was applied into the standardized, 5-mm diameter defects, which were made bilaterally on the parietal bone of the rat. The animals were allowed to heal for 8weeks, and samples were harvested and analyzed by micro-computed tomography and histology. Improved proliferation of rat mesenchymal stem cells was observed with VEGF loaded MC. For osteogenic differentiation, dual growth factors delivered by MC showed higher osteogenic gene expression, alkaline phosphatse production and calcium deposition. The in vivo results revealed statistically significant increase in new bone formation when dual growth factors were delivered by MC. Dual growth factors administered on a calcium phosphate matrix showed significantly enhanced osteogenic potential. We propose this system has potential clinical utility in providing solutions for craniofacial bone defects, with the added benefit of early availability.

Dual delivery of platelet-derived growth factor and bone morphogenetic factor-6 on titanium surface to enhance the early period of implant osseointegration.

To test the surface properties and in vitro effects of a new sequential release system on MC3T3-E1 cells for improved osseointegration. BMP6-loaded anodized titanium coated with PDGF containing silk fibroin (SF) may improve osseointegration. Titanium surfaces were electrochemically anodized, and SF layer was covered via electrospinning. Five experimental groups (unanodized Ti (Ti), anodized Ti (AnTi), anodized+BMP6-loaded Ti (AnTi-BMP6), anodized+BMP6 loaded+silk fibroin-coated Ti (AnTi-BMP6-SF), and anodized+BMP6-loaded+silk fibroin with PDGF-coated Ti (AnTi-BMP6-PDGF-SF)) were tested. After SEM characterization, contact angle analysis, and FTIR analysis, the amount of released PDGF and BMP6 was detected using ELISA. Cell proliferation (XTT), mineralization, and gene expression (RUNX2 and ALPL) were also evaluated. After successful anodization and loading of PDGF and BMP6, contact angle measurements showed hydrophobicity for TiO2 and hydrophilicity for protein-adsorbed surfaces. In FTIR, protein-containing surfaces exhibited amide-I, amide-II, and amide-III bands at 1600cm-1 -1700cm-1 , 1520cm-1 -1540cm-1 , and 1220cm-1 -1300cm-1 spectrum levels with a significant peak in BMP6- and/or SF-loaded groups at 1100cm-1 . PDGF release and BMP6 release were delayed, and relatively slower release was detected in SF-coated surfaces. Higher MC3T3-E1 proliferation and mineralization and lower gene expression of RUNX2 and ALPL were detected in AnTi-BMP6-PDGF-SF toward day 28. The new system revealed a high potential for an improved early osseointegration period by means of a better factor release curve and contribution to the osteoblastic cell proliferation, mineralization, and associated gene expression.

Dual delivery of stem cells and insulin-like growth factor-1 in coacervate-embedded composite hydrogels for enhanced cartilage regeneration in osteochondral defects

Exogenous dual delivery of progenitor cell population and therapeutic growth factors (GFs) is one of alternative tissue engineering strategies for osteochondral tissue regeneration. In the present study, an implantable dual delivery platform was developed using coacervates (Coa) (i.e., a tertiary complex of poly(ethylene argininylaspartate diglyceride) (PEAD) polycation, heparin, and cargo insulin-like growth factor-1 (IGF-1), in thiolated gelatin (gelatin-SH)/ poly(ethylene glycol) diacrylate (PEGDA) interpenetrating network (IPN) hydrogels. Since Coa is able to protect cargo GF and maintain its long-term bioactivity, it is speculated that Coa-mediated delivery of chondrogenic factor IGF-1 with the aid of adipose-derived stem cells (ADSCs) would synergistically facilitate osteochondral tissue repair during physiological regeneration process. Our results indicate that gelatin-SH/PEGDA IPN hydrogels demonstrated biocompatibility and mechanical properties for a possible long-term transplantation, and PEAD-base Coa exhibited a sustained release of bioactive IGF-1 over 3 weeks. Subsequently, released IGF-1 from Coa could effectively induce chondrogenic differentiation of embedded ADSCs in the hydrogel, by showing enhanced glycosaminoglycan deposition and expression of chondrogenesis-associated genes. More importantly, at 12 weeks post-implantation in a rabbit full thickness osteochondral defect model, the quality of regenerative tissues in both chondral and subchondral layers was significantly improved in dual delivery of ADSC and IGF-1 in Coa encapsulated in gelatin-SH/PEGDA IPN hydrogels, as compared with a single delivery of ADSC only and a dual delivery without Coa. Therefore, we conclude that our Coa-embedded composite hydrogel platform could effectively augment osteochondral tissue regeneration holds promise for a feasible osteoarthritis therapeutic application.

Dual local drug delivery of vancomycin and farnesol for mitigation of MRSA infection in vivo - a pilot study.

Surgical site infections after orthopaedic surgery using fracture fixation devices or endosseous implants create major surgical challenges with severe adverse effects, such as osteomyelitis. These infections are frequently caused by Staphylococcus aureus, often with high resistance to antibiotics, such as methicillin-resistant Staphylococcus aureus (MRSA). Due to the formation of impenetrable biofilms on implant surfaces, systemic antibiotic treatment has become exceedingly difficult. New solutions are pursued by combining several drugs using a controlled delivery system from specifically engineered implant surfaces. A sol-gel coating on titanium implants was previously developed with 20 wt % vancomycin and 30 wt % farnesol, with suppression of MRSA in vitro. The present study investigated the efficacy of sol-gel film coatings for controlled dual local delivery over 4 weeks utilising a rat infection model. The findings confirmed the viability of this new concept in vivo based on the differences observed between coatings containing vancomycin alone (SGV) and the dual-drug-containing coating with vancomycin and farnesol (SGVF). While both the SGVF and SGV coatings facilitated excellent preservation of the osseous microarchitecture, SGVF coating displayed a slightly higher potency for suppressing MRSA infiltration than SGV, in combination with a lower reactive bone remodelling activity, most likely by disturbing biofilm formation. The next step for advancing the concept of dual-drug delivery from sol-gel coatings to the clinic and confirming the promising effect of the SGVF coatings on reactive bone remodelling and suppressing MRSA infiltration is a study in a larger animal species with longer time points.

Effects of controlled dual growth factor delivery on bone regeneration following composite bone-muscle injury

The objective of this study was to investigate the controlled release of two growth factors (BMP-2 and VEGF) as a treatment strategy for bone healing in clinically challenging composite injuries, consisting of a femoral segmental bone defect and volumetric muscle loss. This is the first investigation of dual growth factor delivery in a composite injury model using an injectable delivery system consisting of heparin microparticles and alginate gel. The loading efficiency of growth factors into these biomaterials was found to be >90%, revealing a strong affinity of VEGF and BMP-2 to heparin and alginate. The system could achieve simultaneous or tunable release of VEGF and BMP-2 by varying the loading strategy. Single growth factor delivery (VEGF or BMP-2 alone) significantly enhanced vascular growth in vitro. However, no synergistic effect was observed for dual growth factor (BMP-2 + VEGF) delivery in vitro. Effective bone healing was achieved in all treatment groups (BMP-2, simultaneous or tunable delivery of BMP-2 and VEGF) in the composite injury model. The mechanics of the regenerated bone reached a maximum strength of ~52% of intact bone with tunable delivery of VEGF and BMP-2. Overall, simultaneous or tunable co-delivery of low-dose BMP-2 and VEGF failed to fully restore the mechanics of bone in this injury model. Given the severity of the composite injury, VEGF alone may not be sufficient to establish mature and stable blood vessels when compared with previous studies co-delivering BMP-2+VEGF enhanced bone tissue regeneration. Hence, future studies are warranted to develop an alternative treatment strategy focusing on better control over growth factor dose, spatiotemporal delivery, and additional growth factors to regenerate fully functional bone tissue. Statement of SignificanceWe have developed an injectable delivery system consisting of heparin microparticles and an alginate hydrogel that is capable of delivering multiple growth factors in a tunable manner. We used this delivery system to deliver BMP-2 and VEGF in a rodent model of composite bone-muscle injury that mimics clinical type III open fractures. An advanced treatment strategy is necessary for these injuries in order to avoid the negative side effects of high doses of growth factors and because it has been shown that the addition of a muscle injury in this model attenuates the bone regenerative effect of BMP-2. This is the first study to test the effects of dual growth factor delivery (BMP-2/VEGF) on bone healing in a composite bone-muscle injury model and is expected to open up new directions in protein delivery for regenerative medicine.