Controlled delivery of platelet-derived proteins enhances porcine wound healing

Advancements in employing two-dimensional nanomaterials for enhancing skin wound healing: a review of current practice

The two-dimensional nanomaterials are characterized by their ultra-thin structure, diverse chemical functional groups, and remarkable anisotropic properties. Since its discovery in 2004, graphene has attracted significant scientific interest due to its potential applications in various fields, including electronics, energy systems, and biomedicine. In medicine, graphene is used for designing smart drug delivery systems, especially for antibiotics, and biosensing. Skin trauma is a prevalent dermatological condition that increasingly contributes to morbidities and mortalities, thus representing a significant health burden. During tissue damage, rapid skin repair is crucial to prevent blood loss and infection. Therefore, drugs used for skin trauma must possess antimicrobial and anti-inflammatory properties. Two-dimensional (2D) nanomaterials possess remarkable physical, chemical, optical, and biological characteristics due to their uniform shape, increased surface area, and surface charge. Graphene and its derivatives, transition-metal dichalcogenides (TMDs), black phosphorous (BP), hexagonal boron nitride (h-BN), MXene, and metal-organic frameworks (MOFs) are among the commonly used 2D nanomaterials. Moreover, they exhibit antibacterial and anti-inflammatory properties. This review presents a comprehensive discussion of the clinical approaches employed for wound healing treatment and explores the applications of commonly used 2D nanomaterials to enhance wound healing outcomes.

Unraveling mechanisms of protein encapsulation and release in coacervates via molecular dynamics and machine learning

Coacervates play a pivotal role in protein-based drug delivery research, yet their drug encapsulation and release mechanisms remain poorly understood. Here, we utilized the Martini model to investigate bovine serum albumin (BSA) protein encapsulation and release within polylysine/polyglutamate (PLys/PGlu) coacervates. Our findings emphasize the importance of ingredient addition sequence in coacervate formation and encapsulation rates, attributed to preference contact between oppositely charged proteins and poly(amino acid)s. Notably, coacervates composed of β-sheet poly(amino acid)s demonstrate greater BSA encapsulation efficiency due to their reduced entropy and flexibility. Furthermore, we examined the pH responsiveness of coacervates, shedding light on the dissolution process driven by Coulomb forces. By leveraging machine learning algorithms to analyze simulation results, our research advances the understanding of coacervate-based drug delivery systems, with the ultimate goal of optimizing therapeutic outcomes.

A Bionic Thermosensitive Sustainable Delivery System for Reversing the Progression of Osteoarthritis by Remodeling the Joint Homeostasis

Although the pathogenesis of osteoarthritis (OA) is unclear, inflammatory cytokines are related to its occurrence. However, few studies focused on the therapeutic strategies of regulating joint homeostasis by simultaneously remodeling the anti-inflammatory and immunomodulatory microenvironments. Fibroblast growth factor 18 (FGF18) is the only disease-modifying OA drug (DMOAD) with a potent ability and high efficiency in maintaining the phenotype of chondrocytes within cell culture models. However, its potential role in the immune microenvironment remains unknown. Besides, information on an optimal carrier, whose interface and chondral-biomimetic microenvironment mimic the native articular tissue, is still lacking, which substantially limits the clinical efficacy of FGF18. Herein, to simulate the cartilage matrix, chondroitin sulfate (ChS)-based nanoparticles (NPs) are integrated into poly(D, L-lactide)-poly(ethylene glycol)-poly(D, L-lactide) (PLEL) hydrogels to develop a bionic thermosensitive sustainable delivery system. Electrostatically self-assembled ChS and ε-poly-l-lysine (EPL) NPs are prepared for the bioencapsulation of FGF18. This bionic delivery system suppressed the inflammatory response in interleukin-1β (IL-1β)-mediated chondrocytes, promoted macrophage M2 polarization, and inhibited M1 polarization, thereby ameliorating cartilage degeneration and synovitis in OA. Thus, the ChS-based hydrogel system offers a potential strategy to regulate the chondrocyte-macrophage crosstalk, thus re-establishing the anti-inflammatory and immunomodulatory microenvironment for OA therapy.

Triple-layered core-shell fiber dressings with enduring platelet conservation and sustained growth factor release abilities for chronic wound healing

Platelet-rich plasma (PRP) is one of the most popular biomaterials in regenerative medicine. However, the difficulties encountered in its preservation, and the requirement for on-demand preparation severely limit its application. In addition, its rapid degradation in the wound microenvironment makes the sustained release of growth factors impossible and finally reduces the therapeutic effect on chronic wounds. Here, a multifunctional dressing based on triple-layered core-shell fibers for loading and enduring preservation of PRP was developed using a one-step coaxial bioprinting technique combined with freeze-drying. The platelets were effectively dispersed and immobilized in the core layer of the fiber, leading to a sustained release of growth factors from the PRP. The rate of release can be controlled by adjusting the triple-layered core-shell structure. Simultaneously, the triple-layered core-shell structure can reduce the deactivation of PRP during freezing and storage. The experimental findings suggest that PRP exhibits sustained activity, facilitating the process of wound healing even after a storage period of 180 days. Furthermore, the protective mechanism of PRP by the triple-layered core-shell fiber was investigated, and the conditions for freeze-drying and storage were optimized, further enhancing the long-term storability of PRP. As a result, the multifunctional core-shell fiber dressings developed in this study offer a novel approach for sustained growth factor release and the enduring preservation of active PRP.

Platelet-Rich Plasma Composite Organohydrogel with Water-Locking and Anti-Freezing to Accelerate Wound Healing

Hydrogels have gained impressive attention in biological medicine due to their excellent biosafety, softness, and varied functional components. However, conventional hydrogels have inherent defects, such as low tensile strength, weak water-locking, and poor anti-freezing. In tissue engineering, once the hydrogel loses water or freezes, it will harden the interaction interfaces and destroy the nascent granulation tissue. Herein, based on the design concept of "hard frame-soft penetration", a composite adhesive organohydrogel is fabricated by introducing bacterial cellulose and platelet-rich plasma (PRP) into a poly-N-(tris[hydroxymethyl]methyl)acrylamide (THMA)/N-acryloyl aspartic acid (AASP) hybrid gel network infiltrated with glycerol/water binary solvent. The resultant organohydrogels exhibit excellent antifreeze properties at low temperatures (-80 °C) and demonstrate stable long-term water retention (91%) in the open environment within 12 days and can adhere firmly to the tissues by the action of "hydrogen bond clusters". Additionally, the introduction of bacterial cellulose matrix endows the organohydrogel with high tensile strength similar to that of skin. In vivo, the PRP-loaded organohydrogel can release a variety of growth factors to accelerate the wound healing process through collagen deposition and angiogenesis. Altogether, this strategy will extend the life of the hydrogel in some harsh medical environments.

Risk factors for wound healing complications after revascularization for MMD with complete Y-shaped incision

Moyamoya disease (MMD) is a chronic occlusive cerebrovascular disease that can be treated with revascularization. Surgery increases the risk of poor wound healing (PWH) due to the impact on the blood supply to the flap. We aimed to analyze risk factors for PWH in MMD with a complete Y-shaped incision. A total of 125 patients with MMD were enrolled in this prospective observational study. The wounds were assessed and measured on the third and seventh days after surgery. The mean age of these patients was 43.3 ± 10.0 years. The ratio of male to female was 1:1.3. 15 (12.0%) patients had incision complications. 5 patients (4.0%) had redness; 2 patients (1.6%) had swelling; 2 patients (1.6%) had fat necrosis; 3 patients (2.4%) had incision infection; and 3 patients (2.4%) had flap necrosis. Student's t test showed significant differences in BMI (P = 0.040) and fever time (P = 0.050). The standard chi-squared test showed significant differences in incision infection (P = 0.010), suture mode (P = 0.047), and cutting off large branch vessels in the flap (P < 0.001). Multivariate logistic regression analysis suggested that incision infection (P = 0.026, OR 12.958), using a skin stapler (P = 0.030, OR 4.335), cutting off large branch vessels in the flap (P = 0.009, OR 5.227), and BMI (P = 0.027, OR 1.204) were risk factors. The area under the curve for risk factors for PWH on a receiver operating characteristic curve was 0.853. Incision infection, using a skin stapler, higher BMI, and cutting off large branch vessels in the flap are risk factors for PWH.

Coacervate-Filled Lipid Vesicles for Protein Delivery

Macromolecularly crowded coacervate is useful in protein delivery for tissue engineering and regenerative medicine. However, coacervate tends to aggregate easily, which impedes their application. Here, this work presents a method to prepare coacervate with enhanced stability. This work assembles phospholipids on the surface of a coacervate to form lipocoacervate (LipCo). The resultant LipCo possesses a discrete spherical structure with a coacervate interior and phospholipid outer shell. The size of LipCo does not change over the four-week observation window, whereas coacervate coalesced into one bulk phase within 30 min. This work uses vascular endothelial growth factor-C (VEGF-C) and fibroblast growth factor-2 (FGF-2) as examples to test LipCo's ability to maintain protein bioactivity. The in vitro lymphangiogenesis assay demonstrates that human dermal lymphatic endothelial cells (LECs) formed increased network of cord in VEGF-C and FGF-2 loaded LipCo group compared to free proteins and proteins loaded in coacervate. Overall, LipCo could serve as a protein delivery vehicle with improved colloidal stability.

Icy core-shell composite nanofibers with cooling, antibacterial and healing properties for outdoor burns

Burns are usually difficult to treat because their susceptibe to bacterial infections. When burns is accompanied by hyperthermia, the heat accumulated on the skin will causes extensive tissue damage. Most dressings focus on the treatment process, while ignoring the first-aid treatment to remove hyperthermia. To make matters worse, when outdoors, it is hard to find clean water to wash and cool the burned area. A dressing which can simultaneously realize first-time cooling and repairing treatment of the burned area can shorten treatment time, and is especially beneficial for outdoor use. In this study, a handheld coaxial electrospinning device is developed for preparing platelet-rich plasma @Polycaprolactone-epsilon polylysine (PRP@PCL/ε-PL) core-shell nanofibers. The nanofibers can be synchronously transformed into ice fibers during the spinning process, and directly deposited on the skin. The whole process is convenient to use outdoor. Via dual cooling mechanisms, first aid can take away the excessive heat in the burn area by nanofibers. These core-shell nanofibers also show its excellent antimicrobial and tissue regeneration-promoting properties. Therefore, it achieves first-time cooling and repair treatment of the burned area at the same time. Moreover, due to direct in-situ deposition of this handheld coaxial electrospinning, better antimicrobial properties, and faster healing performance are achieved. By using this integrated strategy that combines cooling, antibacterial and healing promotion, the burn recovery time is shortened from 21 days to 14 days.

Delivery of bone morphogenetic protein-2 by crosslinking heparin to nile tilapia skin collagen for promotion of rat calvaria bone defect repair

Collagen has been widely used as a biomaterial for tissue regeneration. At the present, aqua-collagen derived from fish is poorly explored for biomedical material applications due to its insufficient thermal stability. To improve the bone repair ability and thermal stability of fish collagen, the tilapia skin collagen was crosslinked by EDC/NHS with heparin to bind specifically to BMP-2. The thermal stability of tilapia skin collagen crosslinked with heparin (HC-COL) was detected by differential scanning calorimetry (DSC). Cytotoxicity of HC-COL was assessed by detecting MC3T3-E1 cell proliferation using CCK-8 assay. The specific binding of BMP-2 to HC-COL was tested and the bioactivity of BMP-2-loaded HC-COL (HC-COL-BMP-2) was evaluated in vitro by inducing MC3T3-E1 cell differentiation. In vivo, the bone repair ability of HC-COL-2 was evaluated using micro-CT and histological observation. After crosslinking by EDC/NHS, the heparin-linked and the thermostability of the collagen of Nile Tilapia were improved simultaneously. HC-COL has no cytotoxicity. In addition, the binding of BMP-2 to HC-COL was significantly increased. Furthermore, the in vitro study revealed the effective bioactivity of BMP-2 binding on HC-COL by inducing MC3T3-E1 cells with higher ALP activity and the formation of mineralized nodules. In vivo studies showed that more mineralized and mature bone formation was achieved in HC-COL-BMP-2 group. The prepared HC-COL was an effective BMP-2 binding carrier with enough thermal stability and could be a useful biomaterial for bone repair.

Functionalizing multi-component bioink with platelet-rich plasma for customized in-situ bilayer bioprinting for wound healing

In-situ three-dimensional (3D) bioprinting has been emerging as a promising technology designed to rapidly seal cutaneous defects according to their contour. Improvements in the formulations of multi-component bioink are needed to support cytocompatible encapsulation and biological functions. Platelet-rich plasma (PRP), as a source of patient-specific autologous growth factors, exhibits capabilities in tissue repair and rejuvenation. This study aimed to prepare PRP-integrated alginate-gelatin (AG) composite hydrogel bioinks and evaluate the biological effects in vitro and in vivo. 3D bioprinted constructs embedded with dermal fibroblasts and epidermal stem cells were fabricated using extrusion strategy. The integration of PRP not only improved the cellular behavior of seeded cells, but regulate the tube formation of vascular endothelial cells and macrophage polarization in a paracrine manner, which obtained an optimal effect at an incorporation concentration of 5%. For in-situ bioprinting, PRP integration accelerated the high-quality wound closure, modulated the inflammation and initiated the angiogenesis compared with the AG bioink. In conclusion, we revealed the regenerative potential of PRP, readily available at the bedside, as an initial signaling provider in multi-component bioink development. Combined with in-situ printing technology, it is expected to accelerate the clinical translation of rapid individualized wound repair.

The effects of mesenchymal stromal cells and platelet-rich plasma treatments on cutaneous wound healing

Cellular therapy and platelet-rich plasma (PRP) have been used as a treatment for skin wounds. Previous evidence has shown that mesenchymal stromal cells (MSC) may improve skin wound healing. In contrast, contradictory effects have been reported by using PRP treatment on skin wound healing. However, there is evidence that PRP constitutes an excellent scaffold for tissue engineering. In this work, we aim to study the effect of MSC on skin wound healing. We used an experimental murine model of full-thickness wounds. Wounds were treated with human bone marrow-MSC contained in a PRP clot. Untreated or PRP-treated wounds were used as controls. Wound healing was evaluated by macroscopic observation and histological analysis at day 7 post-wounding. Immunohistochemical studies were performed to detect the presence of epithelial progenitor cells (EPC) and the expression of basic fibroblast growth factor (bFGF). MSC/PRP implantation induced a significant wound closure and re-epithelialization as compared with the controls. Increase of CD34⁺ cells and bFGF was observed in the wounds treated with MSC/PRP. Our results show that MSC included in PRP clot induce cutaneous wound repair by promoting re-epithelialization, migration of EPC and expression of bFGF. PRP alone does not exert a significant effect on wound healing. Our results support the possible clinical use of MSC in PRP scaffold as potential treatment of skin wounds.

Enhanced anticancer efficacy of primed natural killer cells via coacervate-mediated exogenous interleukin-15 delivery

Effective exogenous delivery of interleukin (IL)-15 to natural killer (NK) cells with subsequent anticancer efficacy could be a promising immune cell-based cancer immunotherapy. For the protection of encapsulated cargo IL-15 while maintaining its bioactivity under physiological conditions, we utilized a coacervate (Coa) consisting of a cationic methoxy polyethylene glycol-poly(ethylene arginyl aspartate diglyceride) (mPEG-PEAD) polymer, anionic counterpart heparin, and cargo IL-15. mPEGylation into the backbone cation effectively preserved the colloidal stability of Coa in harsh environments and enhanced the protection of cargo IL-15 than normal Coa without mPEGylation. Proliferation and anticancer efficacy of primed NK cells through co-culture with multiple cancer cell lines were enhanced in the mPEG-Coa group due to the maintained bioactivity of cargo IL-15 during the ex vivo expansion of NK cells. These facilitated functions of NK cells were also supported by the increased expression of mRNAs related to anticancer effects of NK cells, including cytotoxic granules, death ligands, anti-apoptotic proteins, and activation receptors. In summary, our Coa-mediated exogenous IL-15 delivery could be an effective ex vivo priming technique for NK cells with sustained immune activation that can effectively facilitate its usage for cancer immunotherapy.

3D printed carboxymethyl cellulose scaffolds for autologous growth factors delivery in wound healing

This work aims to use carboxymethyl cellulose (CMC) as main structural and functional component of 3D printed scaffolds for healing of diabetic wounds. Differently from previous inks involving small contents in CMC, herein sterile (steam-heated) concentrated CMC solely dispersions (10-20%w/v) were screened regarding printability and fidelity properties. CMC (15%w/v)-citric acid inks showed excellent self-healing rheological properties and stability during storage. CMC scaffolds loaded with platelet rich plasma (PRP) sustained the release of relevant growth factors. CMC scaffolds both with and without PRP promoted angiogenesis in ovo, stem cell migration in vitro, and wound healing in a diabetic model in vivo. Transparent CMC scaffolds allowed direct monitoring of bilateral full-thickness wounds created in rat dorsum. CMC scaffolds facilitated re-epithelialization, granulation, and angiogenesis in full-thickness skin defects, and the performance was improved when combined with PRP. Overall, CMC is pointed out as outstanding component of active dressings for diabetic wounds.

Fat grafting and platelet-rich plasma in wound healing: a review of histology from animal studies

Stem cells could form the basis of a novel, autologous treatment for chronic wounds like diabetic foot ulcers. Fat grafts contain adipose-derived stem cells (ADSC) but low survival of cells within the grafts is a major limitation. Platelet-rich plasma (PRP) may increase graft survival. This review examines the histology from animal studies on fat grafting, ADSC and PRP in wound healing. A literature review of major electronic databases was undertaken, and narrative synthesis performed. Data from 30 animal studies were included. ADSC increase angiogenesis over 14 days and often clinically accelerated wound healing. ADSC had a greater effect in animals with impaired wound healing (e.g. diabetes). Activated PRP increased viability of fat grafts. Despite the high number of studies, the quality is variable which weakens the evidence. It does suggest there is a benefit of ADSC, particularly in impaired wound healing. High-quality evidence in humans is required, to establish its clinical usefulness.

Persistent fibrosis and decreased cardiac function following cardiac injury in the Ctenopharyngodon idella (grass carp)

Following the discovery of heart regeneration in zebrafish, several more species within the Cyprinidae family have been found to have the same capability, suggesting heart regeneration may be conserved within this family. Although gonad regeneration has been observed in grass carp (Ctenopharyngodon idella), one of the largest cyprinid fish, the species' response to cardiac injury has not been characterized. Surprisingly, we found cardiomyocytes do not repopulate the injured region following cryoinjury to the ventricle, instead exhibiting unresolved fibrosis and decreased cardiac function that persists for the 8-week duration of this study. Additionally, fibroblasts are likely depleted following injury, a phenomenon not previously described in any cardiac model. The data collected in this study indicate that heart regeneration is unlikely in grass carp (C. idella). It is possible that not all members of the Cyprinidae family possesses regenerative capability observed in zebrafish. Further study of these phenomenon may reveal the underlying differences between regeneration versus unresolved fibrosis in heart disease.

Intralesional platelet-rich plasma injection promotes tongue regeneration following partial glossectomy in a murine model

BACKGROUND

We examined the regenerative efficacy of the activated platelet-rich plasma (PRP) concentrate administered by local injection in an animal model mimicking partial glossectomy for tongue cancer.

METHODS

Four-week-old mice were randomized to four groups; (1) a treatment-naïve control group, (2) a PRP group, (3) a hemiglossectomy group, and (4) a hemiglossectomy + PRP group. The activated PRP concentrate was injected into the deep layer of resected surfaces of mouse tongues immediately after excision, and tongue widths and lengths were measured on postoperative days (POD) 5 and 12. Gross tongue morphologies and microscopic findings were investigated. Inflammation and fibrous tissue areas were also measured, and immunohistochemical analysis was performed for c-kit, neurofilament, and S-100.

RESULTS

The activated PRP concentrate reduced wound scar contracture, promoted wound healing, and reduced inflammation and wound fibrosis. On POD 12, histologic findings in the hemiglossectomy + PRP group were similar to those in the normal control group, and the intensity of stem cell factor receptor c-kit expression was also significantly greater in the PRP group than in the hemiglossectomy group on POD 12. Immunohistochemical staining revealed S100 and neurofilament expressions in the hemiglossectomy + PRP group were significantly more intense than in the hemiglossectomy group.

CONCLUSION

Intralesional activated PRP concentrate injection has potential use for tongue regeneration, wound healing, and neural regeneration with minimal scarring after partial glossectomy.

The Additive Effect of Platelet-Rich Plasma in the Treatment of Actively Bleeding Peptic Ulcer

Background/Aims

Peptic ulcer bleeding is the most common cause of upper gastrointestinal tract bleeding. Platelet-rich plasma (PRP) enhances tissue repair, and is therefore used in various medical treatments. A combination of mechanical or electrothermal hemostasis has been recommended for upper gastrointestinal tract bleeding treatment. This study evaluated the additive efficacy of PRP in bleeding peptic ulcer hemostasis and recovery.

Methods

Eighty patients with peptic ulcer bleeding were initially treated by hemoclipping, and were randomly chosen for either additional PRP (n=40) or additional epinephrine (n=40) injections. Both groups were compared with regard to achieving hemostasis and the frequency of complications.

Results

Hemostasis was immediately achieved in both groups. Two patients (5%) in the PRP group and 8 (20%) patients in the epinephrine group experienced rebleeding after 15.9±2.8 and 12.3±3.7 days, respectively. They were managed by PRP injection in addition to proton pump inhibitor infusion. Hemoglobin was substantially increased in the PRP-treated group with full recovery occurring in 60.5% compared to 31.3% of patients in the epinephrine group (p=0.001). There was no recurrent bleeding in the PRP group, but 4/32 (12.5%) patients in the epinephrine group exhibited rebleeding.

Conclusions

PRP showed additional benefit in reducing peptic ulcer bleeding with no reported significant complications. Clinical trial (NCT03733171).

A composite hydrogel with co-delivery of antimicrobial peptides and platelet-rich plasma to enhance healing of infected wounds in diabetes

Diabetic wound healing remains a major challenge due to its vulnerability to bacterial infection, as well as the less vascularization and prolonged inflammatory phase. In this study, we developed a hydrogel system for the treatment of chronic infected wounds, which can regulate inflammatory (through the use of antimicrobial peptides) and enhance collagen deposition and angiogenesis (through the addition of platelet-rich plasma (PRP)). Based on the formation of Schiff base linkage, the ODEX/HA-AMP/PRP hydrogel was prepared by mixing oxidized dextran (ODEX), antimicrobial peptide-modified hyaluronic acid (HA-AMP) and PRP under physiological conditions, which exhibited obvious inhibition zones against three pathogenic bacterial strains (E. coli, S. aureus and P. aeruginosa) and slow release ability of antimicrobials and growth factors. Moreover, CCK-8, live/dead fluorescent staining and scratch test confirmed that ODEX/HA-AMP/PRP hydrogel could facilitate the proliferation and migration of L929 fibroblast cells. More importantly, in vivo experiments further demonstrated that the prepared hydrogels could significantly improve wound healing in a diabetic mouse infection by regulating inflammation, accelerating collagen deposition and angiogenesis. In addition, prepared hydrogel showed a significant antibacterial activity against S. aureus and P. aeruginosa, inhibited pro-inflammatory factors (TNF-α, IL-1β and IL-6), enhanced anti-inflammatory factors (TGF-β1) and vascular endothelial growth factor (VEGF) production. The findings of this study suggested that the composite hydrogel with AMP and PRP controlled release ability could be used as a promising candidate for chronic wound healing and infection-related wound healing.

Nanoparticle-Assembled Vacuolated Coacervates Control Macromolecule Spatiotemporal Distribution to Provide a Stable Segregated Cell Microenvironment

Membraneless coacervate compartments in the intracellular and pericellular space mediate critical cellular functions. Developing synthetic coacervates that emulate the morphological, physical, and functional complexity of these natural coacervates is challenging but highly desirable. Herein, a generalizable nanoparticle assembly (NPA) strategy is developed, which is applicable to interactive core-shell nanoparticles with different chemical makeups, to fabricate vacuolated coacervates. The obtained NPA coacervates contain stable internal vacuoles to provide segregated microcompartments, which can mediate the spatially heterogeneous distribution of diverse macromolecules via restricted diffusion. It is further shown that the vacuolated NPA coacervates can harbor and retain macromolecular medium supplements to regulate the functions of cells encapsulated in vacuoles. Furthermore, the restricted macromolecule diffusion can be abolished on demand via the triggered coacervate-hydrogel transition, thereby altering the exposure of encapsulated cells to environmental factors. It is believed that the NPA strategy provides new insights into the design principles of hierarchical coacervates that hold promising potential for a wide array of biomedical applications.

Biopolymeric Coacervate Microvectors for the Delivery of Functional Proteins to Cells

The extent to which biologic payloads can be effectively delivered to cells is a limiting factor in the development of new therapies. Limitations arise from the lack of pharmacokinetic stability of biologics in vivo. Encapsulating biologics in a protective delivery vector has the potential to improve delivery profile and enhance performance. Coacervate microdroplets are developed as cell-mimetic materials with established potential for the stabilization of biological molecules, such as proteins and nucleic acids. Here, the development of biodegradable coacervate microvectors (comprising synthetically modified amylose polymers) is presented, for the delivery of biologic payloads to cells. Amylose-based coacervate microdroplets are stable under physiological conditions (e.g., temperature and ionic strength), are noncytotoxic owing to their biopolymeric structure, spontaneously interacted with the cell membrane, and are able to deliver and release proteinaceous payloads beyond the plasma membrane. In particular, myoglobin, an oxygen storage and antioxidant protein, is successfully delivered into human mesenchymal stem cells (hMSCs) within 24 h. Furthermore, coacervate microvectors are implemented for the delivery of human bone morphogenetic protein 2 growth factor, inducing differentiation of hMSCs into osteoprogenitor cells. This study demonstrates the potential of coacervate microdroplets as delivery microvectors for biomedical research and the development of new therapies.

Platelet-Rich Plasma Therapy in the Treatment of Diseases Associated with Orthopedic Injuries

Platelet-rich plasma (PRP) is an autologous platelet concentrate prepared from the whole blood that is activated to release growth factors (GFs) and cytokines and has been shown to have the potential capacity to reduce inflammation and improve tissue anabolism for regeneration. The use of PRP provides a potential for repair due to its abundant GFs and cytokines, which are key in initiating and modulating regenerative microenvironments for soft and hard tissues. Among outpatients, orthopedic injuries are common and include bone defects, ligament injury, enthesopathy, musculoskeletal injury, peripheral nerve injury, chronic nonhealing wounds, articular cartilage lesions, and osteoarthritis, which are caused by trauma, sport-related or other types of trauma, or tumor resection. Surgical intervention is often required to treat these injuries. However, for numerous reasons regarding limited regeneration capacity and insufficient blood supply of the defect region, these treatments commonly result in unsatisfactory outcomes, and follow-up treatment is challenging. The aim of the present review is to explore future research in the field of PRP therapy in the treatment of diseases associated with orthopedic injuries. Impact statement In recent years, platelet-rich plasma (PRP) has become widely used in the treatment of diseases associated with orthopedic injuries, and the results of numerous studies are encouraging. Due to diseases associated with orthopedic injuries being common in clinics, as a conservative treatment, more and more doctors and patients are more likely to accept PRP. Importantly, PRP is a biological product of autologous blood that is obtained by a centrifugation procedure to enrich platelets from whole blood, resulting in few complications, such as negligible immunogenicity from an autologous source, and it is also simple to produce through an efficient and cost-effective method in a sterile environment. However, the applicability, advantages, and disadvantages of PRP therapy have not yet been fully elucidated. The aim of the present review is to explore future research in the field of PRP therapy in the treatment of diseases associated with orthopedic injuries, as well as to provide references for clinics.

Skin wound healing assisted by angiogenic targeted tissue engineering: A comprehensive review of bioengineered approaches

Skin injuries and in particular, chronic wounds, are one of the major prevalent medical problems, worldwide. Due to the pivotal role of angiogenesis in tissue regeneration, impaired angiogenesis can cause several complications during the wound healing process and skin regeneration. Therefore, induction or promotion of angiogenesis can be considered as a promising approach to accelerate wound healing. This article presents a comprehensive overview of current and emerging angiogenesis induction methods applied in several studies for skin regeneration, which are classified into the cell, growth factor, scaffold, and biological/chemical compound-based strategies. In addition, the advantages and disadvantages of these angiogenic strategies along with related research examples are discussed in order to demonstrate their potential in the treatment of wounds.

Engineering Thermo-pH Dual Responsive Hydrogel for Enhanced Tumor Accumulation, Penetration, and Chemo-Protein Combination Therapy

Purpose

Combined chemotherapeutic drug and protein drug has been a widely employed strategy for tumor treatment. To realize both tumor accumulation and deep tumor penetration for drugs with different pharmacokinetics, we propose a structure-transformable, thermo-pH dual responsive co-delivery system to co-load granzyme B/docetaxel (GrB/DTX).

Methods

Thermo-sensitive hydrogels based on diblock copolymers (mPEG-b-PELG) were synthesized through ring opening polymerization. GrB/DTX mini micelles (GDM) was developed by co-loading these two drugs in pH-sensitive mini micelles, and the GDM-incorporated thermo-sensitive hydrogel (GDMH) was constructed. The thermo-induced gelation behavior of diblock copolymers and the physiochemical properties of GDMH were characterized. GDMH degradation and deep tumor penetration of released mini micelles were confirmed. The pH-sensitive disassembly and lysosomal escape abilities of released mini micelles were evaluated. In vitro cytotoxicity was studied using MTT assays and the in vivo antitumor efficacy study was evaluated in B16-bearing C57BL/6 mice.

Results

GDMH was gelatinized at body temperature and can be degraded by proteinase to release mini micelles. The mini micelles incorporated in GDMH can achieve deep tumor penetration and escape from lysosomes to release GrB and DTX. MTT results showed that maximum synergistic antitumor efficacy of GrB and DTX was observed at mass ratio of 1:100. Our in vivo antitumor efficacy study showed that GDMH inhibited tumor growth in the subcutaneous tumor model and in the post-surgical recurrence model.

Conclusion

The smart-designed transformable GDMH can facilitate tumor accumulation, deep tumor penetration, and rapid drug release to achieve synergistic chemo-protein therapy.

Prospects for the application of growth factors in wound healing

As the largest organ of the body, human skin is multifunctional and enjoys two layers, the epidermis and the dermis, the separation of which is performed by a basement membrane zone. Skin protects the body against mechanical forces and infections. Skin wounds represent large and growing challenges to the healthcare systems globally. Skin wound healing, as a protective shield for the body against the external environment, includes interactions among cell types, the neurovascular system, cytokines, and matrix remodeling. Growth factors (GFs) affect the microenvironment of the wound, and cause rises in cell differentiation, proliferation, and migration. Administrating exogenous GFs has revealed potential in enhancing wound healing outcomes. The use of human GFs in the field of wound healing is becoming gradually more interesting, because of the low-invasive techniques required for their use. Reviewed here are the literatures on the healing of skin wounds with emphasize on the role of GFs and their future prospects, containing profits, and probable long-standing side effects accompanied with their use.

A comparison of BMP2 delivery by coacervate and gene therapy for promoting human muscle-derived stem cell-mediated articular cartilage repair

Background

Osteoarthritis and cartilage injury treatment is an unmet clinical need. Therefore, development of new approaches to treat these diseases is critically needed. Previous work in our laboratory has shown that murine muscle-derived stem cells (MDSCs) can efficiently repair articular cartilage in an osteochondral and osteoarthritis model. However, the cartilage repair capacity of human muscle-derived stem cells has not been studied which prompt this study.

Method

In this study, we tested the in vitro chondrogenesis ability of six populations of human muscle-derived stem cells (hMDSCs), before and after lenti-BMP2/GFP transduction using pellet culture and evaluated chondrogenic differentiation of via histology and Raman spectroscopy. We further compared the in vivo articular cartilage repair of hMDSCs stimulated with BMP2 delivered through coacervate sustain release technology and lenti-viral gene therapy-mediated gene delivery in a monoiodoacetate (MIA)-induced osteoarthritis (OA) model. We used microCT and histology to evaluate the cartilage repair.

Results

We observed that all hMDSCs were able to undergo chondrogenic differentiation in vitro. As expected, lenti-BMP2/GFP transduction further enhanced the chondrogenic differentiation capacities of hMDSCs, as confirmed by Alcian blue and Col2A1staining as well as Raman spectroscopy analysis. We observed through micro-CT scanning, Col2A1 staining, and histological analyses that delivery of BMP2 with coacervate could achieve a similar articular cartilage repair to that mediated by hMDSC-LBMP2/GFP. We also found that the addition of soluble fms-like tyrosine kinase-1 (sFLT-1) protein further improved the regenerative potential of hMDSCs/BMP2 delivered through the coacervate sustain release technology. Donor cells did not primarily contribute to the repaired articular cartilage since most of the repair cells are host derived as indicated by GFP staining.

Conclusions

We conclude that the delivery of hMDSCs and BMP2 with the coacervate technology can achieve a similar cartilage repair relative to lenti-BMP2/GFP-mediated gene therapy. The use of coacervate technology to deliver BMP2/sFLT1 with hMDSCs for cartilage repair holds promise for possible clinical translation into an effective treatment modality for osteoarthritis and traumatic cartilage injury.

Self-assembling in situ gel based on lyotropic liquid crystals containing VEGF for tissue regeneration

Current tissue-regenerative biomaterials confront two critical issues: the uncontrollable delivery capacity of vascular endothelial growth factor (VEGF) for adequate vascularization and the poor mechanical properties of the system for tissue regeneration. To overcome these two issues, a self-assembling in situ gel based on lyotropic liquid crystals (LLC) was developed. VEGF-LLC was administrated as a precursor solution that would self-assemble into an in situ gel with well-defined internal inverse bicontinuous cubic phases when exposed to physiological fluid at a defect site. The inverse cubic phase with a 3D bicontinuous water channel enabled a 7-day sustained release of VEGF. The release profile of VEGF-LLC was controlled using octyl glucoside (OG) as a hydration-modulating agent, which could enlarge the water channel, yielding a 2-fold increase in water channel size and a 7-fold increase in VEGF release. For the mechanical properties, the elastic modulus was found to decrease from ∼100 kPa to ∼1.2 kPa, which might be more favorable for angiogenesis. Furthermore, the self-recovery ability of the VEGF-LLC gel was confirmed by quick recovery of the inner network in step-strain measurements. In vitro, VEGF-LLC considerably promoted the proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) as compared to free VEGF (p < 0.05). Furthermore, angiogenesis was successfully induced in rats after subcutaneous injection of VEGF-LLC. The self-assembling LLC gel showed satisfactory degradability and mild inflammatory response with little impact on the surrounding tissue. The controllable release profile and unique mechanical properties of VEGF-LLC offer a new approach for tissue regeneration. STATEMENT OF SIGNIFICANCE: The potential clinical use of currently available biomaterials in tissue regeneration is limited by their uncontrollable drug delivery capacity and poor mechanical properties. Herein, a self-assembling in situ gel based on lyotropic liquid crystals (LLC) for induced angiogenesis was developed. The results showed that the addition of octyl glucoside (OG) could change the water channel size of LLC, which enabled the LLC system to release VEGF in a sustained manner and to possess a suitable modulus to favor angiogenesis simultaneously. Moreover, the self-recovery capability allowed the gel to match the deformation of surrounding tissues during body motion to maintain its properties and reduce discomfort. In vivo, angiogenesis was induced by VEGF-LLC 14 days after administering subcutaneous injection. These results highlight the potential of LLC as a promising sustained protein drug delivery system for vascular formation and tissue regeneration.

Impact of platelet-rich plasma on cell migration processes after external radiation

BACKGROUND

To overcome the compromised wound healing in radiation induced chronic wounds platelet-rich plasma (PRP), as therapeutic agent, is current subject of studies. PRP is associated with pro-angiogenic effects. Nevertheless, effects of platelet-rich plasma in cutaneous wound healing processes are poorly understood so far.

METHODS

In this study, the migration of endothelial cells, fibroblasts and keratinocytes in conjunction with platelet-rich plasma treatment is investigated in the context of radiation effects. Additionally, cell proliferation and viability after external radiation was analyzed regarding treatment by platelet-rich plasma.

RESULTS

All cell cultures showed a trend towards decreasing proliferation and viability after irradiation irrespective of PRP. Upon PRP treatment, irradiated fibroblasts as well as endothelial cells showed an enhanced proliferation whereas proliferation and viability of keratinocytes was reduced after PRP treatment. Scratch assays support the positive effect of PRP on fibroblast and endothelial cell migration, whereas a negative effect on keratinocytes was observed after PRP treatment.

CONCLUSIONS

The present study documents both deleterious effects of external radiation as well as the protective effect of PRP. In summary, increased viability, proliferation and migration are indeed a consequence of the pro-proliferative effect exerted by PRP. Therefore, treatment with PRP products might be useful in the management of chronic radiogenic wounds.

Advanced drug delivery systems and artificial skin grafts for skin wound healing

Cutaneous injuries, especially chronic wounds, burns, and skin wound infection, require painstakingly long-term treatment with an immense financial burden to healthcare systems worldwide. However, clinical management of chronic wounds remains unsatisfactory in many cases. Various strategies including growth factor and gene delivery as well as cell therapy have been used to enhance the healing of non-healing wounds. Drug delivery systems across the nano, micro, and macroscales can extend half-life, improve bioavailability, optimize pharmacokinetics, and decrease dosing frequency of drugs and genes. Replacement of the damaged skin tissue with substitutes comprising cell-laden scaffold can also restore the barrier and regulatory functions of skin at the wound site. This review covers comprehensively the advanced treatment strategies to improve the quality of wound healing.

Keratinocyte Migration in a Three-Dimensional In Vitro Wound Healing Model Co-Cultured with Fibroblasts

Background

Because three-dimensional (3D) models more closely mimic native tissues, one of the goals of 3D in vitro tissue models is to aid in the development and toxicity screening of new drug therapies. In this study, a 3D skin wound healing model comprising of a collagen type I construct with fibrin-filled defects was developed.

Methods

Optical imaging was used to measure keratinocyte migration in the presence of fibroblasts over 7 days onto the fibrin-filled defects. Additionally, cell viability and growth of fibroblasts and keratinocytes was measured using the alamarBlue^® assay and changes in the mechanical stiffness of the 3D construct was monitored using compressive indentation testing.

Results

Keratinocyte migration rate was significantly increased in the presence of fibroblasts with the cells reaching the center of the defect as early as day 3 in the co-culture constructs compared to day 7 for the control keratinocyte monoculture constructs. Additionally, constructs with the greatest rate of keratinocyte migration had reduced cell growth. When fibroblasts were cultured alone in the wound healing construct, there was a 1.3 to 3.4-fold increase in cell growth and a 1.2 to 1.4-fold increase in cell growth for keratinocyte monocultures. However, co-culture constructs exhibited no significant growth over 7 days. Finally, mechanical testing showed that fibroblasts and keratinocytes had varying effects on matrix stiffness with fibroblasts degrading the constructs while keratinocytes increased the construct's stiffness.

Conclusion

This 3D in vitro wound healing model is a step towards developing a mimetic construct that recapitulates the complex microenvironment of healing wounds and could aid in the early studies of novel therapeutics that promote migration and proliferation of epithelial cells.

Review: Multimodal bioactive material approaches for wound healing

Wound healing is a highly complex process of tissue repair that relies on the synergistic effect of a number of different cells, cytokines, enzymes, and growth factors. A deregulation in this process can lead to the formation of a non-healing chronic ulcer. Current treatment options, such as collagen wound dressings, are unable to meet the demand set by the wound environment. Therefore, a multifaceted bioactive dressing is needed to elicit a targeted affect. Wound healing strategies seek to develop a targeted effect through the delivery of a bioactive molecule to the wound by a hydrogel or a polymeric scaffold. This review examines current biomaterial and small molecule-based approaches that seek to develop a bioactive material for targeted wound therapy and accepted wound healing models for testing material efficacy.

Biodegradable Scaffolds for Bone Regeneration Combined with Drug-Delivery Systems in Osteomyelitis Therapy

A great deal of research is ongoing in the area of tissue engineering (TE) for bone regeneration. A possible improvement in restoring damaged tissues involves the loading of drugs such as proteins, genes, growth factors, antibiotics, and anti-inflammatory drugs into scaffolds for tissue regeneration. This mini-review is focused on the combination of the local delivery of antibiotic agents with bone regenerative therapy for the treatment of a severe bone infection such as osteomyelitis. The review includes a brief explanation of scaffolds for bone regeneration including scaffolds characteristics and types, a focus on severe bone infections (especially osteomyelitis and its treatment), and a literature review of local antibiotic delivery by the combination of scaffolds and drug-delivery systems. Some examples related to published studies on gentamicin sulfate-loaded drug-delivery systems combined with scaffolds are discussed, and future perspectives are highlighted.