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Light has attracted significant attention as a promising tool in the biomedical and cosmetic industries. However, little is known about the cytotoxic effects of conventional light sources based on their physical effects such as temperature and luminance. Here, the cytotoxic effects of representative light sources, a light-emitting diode (LED) and an organic light-emitting diode (OLED), were studied with human adipose-derived stem cells (hADSCs). Regardless of the identical light energy conditions, LED group induced a higher apoptotic activity in hADSCs than the OLED group due to its significant heat generation compared to OLED as further demonstrated with heat shock protein family gene expression. Additionally, we further confirmed the effect of luminance by irradiating light from LED and OLED under the same temperature and energy conditions. Increased cell proliferation was confirmed in the OLED group, and a significant expression of intracellular reactive oxygen species was observed in the LED group without showing heat shock protein upregulation. Taken together, the differences in cytotoxicity and cellular response after LED irradiation compared with OLED irradiation can be varied with temperature and luminance control. This study suggests that OLED based device could be an alternative and promising light source for future biomedical and cosmetic applications.

The restoration of damaged endothelium is promising to reduce side effects, including restenosis and thrombosis, in the stent treatment for vascular diseases. Current technologies based on drug delivery for these complications still do not satisfy patients due to invariant recurrence rate. Recently, even if one approach was applied to clinical trial to develop the firstly commercialized stent employing circulating endothelial progenitor cells (EPCs) in blood vessels, it resulted in failure in clinical trial. Based on instruction of the failed case, we designed an advanced EPC-capture stent covered with anti-CD146 antibody (Ab) immobilized silicone nanofilament (SiNf) for the highly efficient and specific capture of not early but late stage of EPCs. In vitro cell capture test demonstrates enhanced capture efficiency and adhesion morphology of late EPCs on the modified substrate. The modified substrates could capture 8 times more late EPCs and even 3 times more mesenchymal stem cells (MSCs) as compared to unmodified one. A porcine model with high similarity to human reproduced in vivo results ideally translated from in vitro cell capture results. As restenosis indicators, lumen area, neointimal rate and stenosis area for modified stents were reduced at the range of 30-60% as compared to those for bare metal stent (BMS). Fibrin score indicating thrombosis was lowered less than half as comparing to that on BMS. These inspiring results are attributed to ~2-fold increased endothelial coverage, determined by immuno-histological staining. Taken together, the CD146 Ab-armed nanofilamentous stent could show great performance in the reduction of thrombosis and restenosis through re-endothelialization due to highly efficient specific cell capture. STATEMENT OF SIGNIFICANCE: Stents have been developed from simple metal stents to functionalized stents for past decades. However, they have still risks to relapse the occlusion in stented arteries. In this paper, we describe the fabrication and optimization of cell capturing stents to maximize the effective re-endothelialization through the serial coating of silicone nanofilaments and anti-CD146 antibody. The nanofilaments increase the amount of coated antibodies and provide the anchoring points of circulating angiogenic cells for strong focal adhesion. We demonstrate high immobilizing ability of circulating angiogenic cells (endotheliali progenitor cells and mesenchymal stem cells) in vitro under similar shear stress to coronary arteries (15 dyne/cm2). Also, we show accelerating re-endothelialization and the efficient prevention of restenosis in porcine coronary arteries in vivo.

Background Human adipose-derived stem cells (hADSCs) have been used in various fields of tissue engineering because of their promising therapeutic efficacy. However, the stemness of hADSCs cannot be maintained for long durations, and their therapeutic cellular functions, such as paracrine factor secretion decrease during long-term cell culture. To facilitate the use of long-term-cultured hADSCs (L-ADSCs), we designed a novel therapeutic anti-senescence ion-delivering nanocarrier (AIN) that is capable of recovering the therapeutic properties of L-ADSCs. In the present study, we introduced a low-pH-responsive ion nanocarrier capable of delivering transition metal ions that can enhance angiogenic paracrine factor secretion from L-ADSCs. The AINs were delivered to L-ADSCs in an intracellular manner through endocytosis. Results Low pH conditions within the endosomes induced the release of transition metal ions (Fe) into the L-ADSCs that in turn caused a mild elevation in the levels of reactive oxygen species (ROS). This mild elevation in ROS levels induced a downregulation of senescence-related gene expression and an upregulation of stemness-related gene expression. The angiogenic paracrine factor secretion from L-ADSCs was significantly enhanced, and this was evidenced by the observed therapeutic efficacy in response to treatment of a wound-closing mouse model with conditioned medium obtained from AIN-treated L-ADSCs that was similar to that observed in response to treatment with short-term-cultured adipose-derived stem cells. Conclusions This study suggests a novel method and strategy for cell-based tissue regeneration that can overcome the limitations of the low stemness and therapeutic efficacy of stem cells that occurs during long-term cell culture. Graphical Abstract

Drug-eluting stents (DESs) have been used for the treatment of cardiovascular diseases including stenosis. However, in-stent restenosis, thrombosis, and delayed re-endothelialization represent challenges for their clinical applications. Here, we demonstrate a novel work to overcome these limitations through surface modification technology. The cobalt-chromium (Co-Cr) surface was modified with antioxidants such as gallic acid (GA) and rutin (Ru) and the corresponding persulfates derivatives (i.e., GAS, and RuS) through a simple conjugation procedure. Various analyses tools such as ATR-FTIR, XPS, water contact angle, SEM, and AFM characterized the functionalized surface. The surface characterization confirmed that the antioxidant and the additional persulfates were successfully bonded to the Co-Cr surface. The results of in vitro endothelial cells proved that the persulfates derivatives showed the highest tendency to get rapid re-endothelialization especially RuS. In addition, it showed inhibition to smooth muscle cells (SMCs) as compared to control Co-Cr substrate. The persulfates modified substrates reduced the amount of adsorbed fibrinogen and albumin with higher stability to fetal bovine serum. Moreover, platelet study also demonstrated that Ru and RuS presented lower platelet adhesion with round shape morphology, whereas the control Co-Cr adhere and activate many platelets with pseudopodium morphology. Moreover, these modification processes did not cause any inflammatory responses. In conclusion, it is believed that the persulfates flavonoids have a great potential in the field of drug-eluting stents and blood contacting medical implants to improve blood compatibility, suppress SMCs, and get rapid re-endothelialization.

Kidney diseases are a worldwide public health issue. Renal tissue regeneration using functional scaffolds with biomaterials has attracted a great deal of attention due to limited donor organ availability. Here, we developed a bioinspired scaffold that can efficiently induce renal tissue regeneration. The bioinspired scaffold was designed with poly(lactide-co-glycolide) (PLGA), magnesium hydroxide (Mg(OH)2), and decellularized renal extracellular matrix (ECM). The Mg(OH)2 inhibited materials-induced inflammatory reactions by neutralizing the acidic microenvironment formed by degradation products of PLGA, and the acellular ECM helped restore the biological function of kidney tissues. When the PLGA/ECM/Mg(OH)2 scaffold was implanted in a partially nephrectomized mouse model, it led to the regeneration of renal glomerular tissue with a low inflammatory response. Finally, the PLGA/ECM/Mg(OH)2 scaffold was able to restore renal function more effectively than the control groups. These results suggest that the bioinspired scaffold can be used as an advanced scaffold platform for renal disease treatment., PLGA scaffold with Mg(OH)2 and renal ECM facilitates kidney reconstruction (histological structure and biological function) by neutralizing the acidic microenvironment and improving biocompatibility.

Synthetic biodegradable polymers including poly(lactide-co-glycolide) (PLGA) have been widely used as alternatives to metallic implantable materials in the orthopedic field due to their superior biocompatibility and biodegradability. However, weak mechanical properties of the biodegradable polymers and inflammatory reaction caused by the acidic degradation products have limited their biomedical applications. In this study, we have developed a PLGA composite containing beta-tricalcium phosphate (β-TCP) and magnesium hydroxide (Mg(OH)2) as additives to improve mechanical, osteoconductivity, and anti-inflammation property of the biopolymer composite simultaneously. The β-TCP has an osteoconductive effect and the Mg(OH)2 has a pH neutralizing effect. The PLGA/inorganic composites were uniformly blended via a twin extrusion process. The mechanical property of the PLGA/β-TCP/Mg(OH)2 composite was improved compared to the pure PLGA. In particular, the addition of Mg(OH)2 suppressed the inflammatory reaction of normal human osteoblast (NHOst) cells and also inhibited the differentiation of pre-osteoclastic cells into osteoclasts. Moreover, synergistically upregulated late osteogenic differentiation of NHOst cells was observed on the PLGA/β-TCP/Mg(OH)2 composite. Taken all together, we believe that the use of β-TCP and Mg(OH)2 as additives with synthetic biodegradable polymers has great potential by the synergistic effect in orthopedic applications.

In this study, a polydioxanone (PDO) and poly(L-lactic acid) (PLLA) sheath-core biphasic monofilament was designed to develop an esophageal stent with improved mechanical properties and controlled biodegradability. The radial force of PDO/PLLA sheath-core stent was 10.24 N, while that of PDO stent was 5.64 N. Deteriorations of tensile strength, elastic modulus and elongation during degradation test were also delayed on PDO/PLLA group. Hyaluronic acid–dopamine conjugate and BaSO4/PDO conjugate coating layers provided improved tissue adhesion strength and reasonable X-ray contrast, respectively. Taken all together, the sheath-core filaments with tissue adhesive and radiopaque properties will be useful in designing esophageal stents.

Fibroblast-derived extracellular matrix (fECM)-supported scaffolds made up of poly(lactic-co-glycolic acid) were prepared with the enhanced preservation of ECM components by composites with magnesium hydroxide nanoparticles (MH NPs), and were applied for the renal tissue regeneration. MH NP utilization resulted in an increased ECM protein amount, decreased scaffold degradation, and surface hydrophilic modification. These effects were correlated with the improved adhesion and viability of renal proximal tubule epithelial cells on the scaffold. In vivo experiments demonstrated effects of fECM and MH NPs on renal regeneration. The number of glomeruli was the largest in the ECM scaffold with MH NPs as compared to the pristine scaffold and ECM scaffold without MH NPs. Quantitative PCR analysis exhibited less inflammation (IL-1β, TNF-α, and IL-6) and fibrosis-related (vimentin, collagen I, and α-SMA) markers, whereas opposite results were found in regeneration-related markers (Pax2, vWf, Wt1, and Emx2). The concentration of renal function-related molecules, creatinine and blood urea nitrogen diminished in the ECM scaffold with MH NPs. All results indicate that MH NPs utilization for the renal regenerative scaffold is effective for in vitro and in vivo environments and is, therefore, a good model for regeneration of kidneys and other tissues, and organs.

Atherosclerotic plaques within the vasculature may eventually lead to heart failure. Currently, cardiac stenting is the most effective and least invasive approach to treat this disease. However, in-stent restenosis is a complex chronic side effect of stenting treatment. This study used coronary stents coated with stem cells secreting angiogenic growth factors via an inducible genome-editing system to reduce stent restenosis and induce re-endothelialization within the artery. The characteristics of the cells and their adhesion properties on the stents were confirmed, and the stents were transplanted into a swine model to evaluate restenosis and the potential therapeutic use of stents with stem cells. Restenosis was evaluated using optical coherence tomography (OCT), microcomputed tomography (mCT) and angiography, and re-endothelialization was evaluated by immunostaining after cardiac stent treatment. Compared to a bare metal stent (BMS) or a parental umbilical cord blood-derived mesenchymal stem cell (UCB-MSC)-coated stent, the stents with stem cells capable of the controlled release of hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) successfully reduced restenosis within the stent and induced natural re-endothelialization. Furthermore, UCB-MSCs exhibited the ability to differentiate into endothelial cells in Matrigel, and HGF and VEGF improved this differentiation. Our study indicates that stents coated with UCB-MSCs secreting VEGF/HGF reduce the restenosis side effects of cardiac stenting with improved re-endothelialization.

Artificial scaffolds made up of various synthetic biodegradable polymers have been reported to have many advantages including cheap manufacturing, easy scale up, high mechanical strength, convenient manipulation, and molding into an unlimited variety of shapes. However, the synthetic biodegradable polymers still have the insufficiency for cartilage regeneration owing to their acidic degradation products. To reduce acidification by degradation of synthetic polymers, we incorporated magnesium hydroxide (MH) nanoparticles into porous polymer scaffold not only to effectively neutralize the acidic hydrolysate but also to minimize the structural disturbance of scaffolds. The neutralization effect of poly(D,L-lactic-co-glycolic acid; PLGA)/MH scaffold was confirmed with the maintenance of neutral pH, contrary to a PLGA scaffold with low pH. Further, the scaffolds were applied to evaluate the chondrogenic differentiation of the human bone marrow mesenchymal stem cells. In in vitro study, the PLGA/MH scaffold enhanced the chondrogenesis markers and reduced the calcification, compared to the PLGA scaffold. Additionally, the PLGA/MH scaffold reduced the release of inflammatory cytokines, compared to the PLGA scaffold, as the cell death decreased. Moreover, the addition of MH reduced necrotic cell death at the early stage of chondrogenic differentiation. Further, the necrotic cell death by the PLGA scaffold was mediated by cleavage of caspase-1, the so-called interleukin 1-converting enzyme, and MH alleviated it as well as nuclear factor kappa B expression. Furthermore, the PLGA/MH scaffold highly supported chondrogenic healing of rat osteochondral defect sites in in vivo study. Therefore, it was suggested that a synthetic polymer scaffold containing MH could be a novel healing tool to support cartilage regeneration and further treatment of orthopedic patients. Statement of Significance Synthetic polymer scaffolds have been widely utilized for tissue regeneration. However, they have a disadvantage of releasing acidic products through degradation. This paper demonstrated a novel type of synthetic polymer scaffold with pH-neutralizing ceramic nanoparticles composed of magnesium hydroxide for cartilage regeneration. This polymer showed pH-neutralization property during polymer degradation and significant enhancement of chondrogenic differentiation of mesenchymal stem cells. It reduced not only chondrogenic calcification but also release of proinflammatory cytokines. Moreover, it has an inhibitory effect on necrotic cell death, particularly caspase-1-mediated necrotic cell death (pyroptosis). In in vivo study, it showed higher healing rate of the damaged cartilage in a rat osteochondral defect model. We expected that this novel type of scaffold can be effectively applied to support cartilage regeneration and further treatment of orthopedic patients.

Biodegradable polymers have been extensively used in biomedical applications, ranging from regenerative medicine to medical devices. However, the acidic byproducts resulting from degradation can generate vigorous inflammatory reactions, often leading to clinical failure. We present an approach to prevent acid-induced inflammatory responses associated with biodegradable polymers, here poly(lactide- co-glycolide), by using oligo(lactide)-grafted magnesium hydroxide (Mg(OH)2) nanoparticles, which neutralize the acidic environment. In particular, we demonstrated that incorporating the modified Mg(OH)2 nanoparticles within degradable coatings on drug-eluting arterial stents efficiently attenuates the inflammatory response and in-stent intimal thickening by more than 97 and 60%, respectively, in the porcine coronary artery, compared with that of drug-eluting stent control. We also observed that decreased inflammation allows better reconstruction of mouse renal glomeruli in a kidney tissue regeneration model. Such modified Mg(OH)2 nanoparticles may be useful to extend the applicability and improve clinical success of biodegradable devices used in various biomedical fields.

Vascular stent is tubular shaped medical device designed to treat occluded circulatory or digestive systems by opening the blocked vascular sites. Originally stents were made of bare metals, such as stainless steel and cobalt–chromium alloys, due to their inherent corrosion resistance and good mechanical properties. Damage of intimal layer during expansion of stent, however, have caused neointimal hyperplasia resulting in in-stent restenosis which is one of main complications of vascular stent treatment. Drug-eluting stents (DESs) were introduced to alleviate this restenosis by local delivery of anti-proliferative drugs to the implanted or inserted site. The DES systems have been developed over the years by making changes in its main component, namely, drug, polymeric coating layer and expandable scaffold. Nevertheless, late thrombosis caused by drugs themselves and polymeric coating layer still remains as a serious problem of DES systems. Numerous studies, therefore, consistently focus on more advanced DES systems to solve the current issues. In this mini review article, we cast an opinion on how to improve the potential of DES system by means of (i) summarizing the history of DES system developed so far and (ii) updating current advances for the future generation of DES system.

Several developments are in progress for improving the performance of drug-eluting stents (DESs) including use of biodegradable polymers, polymer-free DES, fully bioabsorbable stents, and so on. The commercially available DESs still suffer from polymer defects that could affect the performance of a DES through a series of adverse events such as coating delamination and/or peeling-off that lead to non-uniform local drug distribution, restenosis, and thrombosis. The goal of this work was to enhance the stability of drug-in-polymer matrix coating on a stent metal surface through surface modification. The cobalt–chromium (Co–Cr) surface was chemically modified using poly(dopamine) (PDA) nano-coating and poly(L-lactide) (PLLA) nano-brush in order to be applied to a biodegradable polymer-coated DES. The biodegradable polymer loaded with sirolimus was coated using an ultrasonic spray coating instrument. The coating morphology on all samples showed a very smooth and uniform coating. The stability of the coating was evaluated for 2 months under the circulation system in which the drug-in-polymer coating on the PLLA brush-modified stent presented the most stable coating behavior as compared to other samples. The in vitro sirolimus release study from both unmodified and modified stents was studied in phosphate-buffered saline (PBS), and the modified stents showed slower sirolimus release profile as compared to unmodified stents. In vivo study was performed in a porcine coronary artery injury model for 28 days. The percentage of in-stent restenosis area (ISR) for PLLA brush-modified sirolimus-eluting stent (SES) decreased significantly as compared to unmodified SES and bare metal stent (BMS). This study demonstrated that the modification of stent surface using PLLA brushes affects in vitro and in vivo performance effectively to be applied for biodegradable polymercoated DES.

The sustained or controlled release of nitric oxide (NO) can be the most promising approach for the suppression or prevention of restenosis and thrombosis caused by stent implantation. The aim of this study is to investigate the feasibility in the potential use of layer-by-layer (LBL) coating with a NO donor-containing liposomes to control the release rate of NO from a metallic stent. Microscopic observation and surface characterizations of LBL-modified stents demonstrate successful LBL coating with liposomes on a stent. Release profiles of NO show that the release rate is sustained up to 5 d. In vitro cell study demonstrates that NO release significantly enhances endothelial cell proliferation, whereas it markedly inhibits smooth muscle cell proliferation. Finally, in vivo study conducted with a porcine coronary injury model proves the therapeutic efficacy of the NO-releasing stents coated by liposomal LBL technique, supported by improved results in luminal healing, inflammation, and neointimal thickening except thrombo-resistant effect. As a result, all these results demonstrate that highly optimized release rate and therapeutic dose of NO can be achieved by LBL coating and liposomal encapsulation, followed by significantly efficacious outcome in vivo.

The restoration of a damaged endothelium might be a fascinating way to reduce significantly late-thrombosis and restenosis in the stent treatment. It has been recently reported that the recruitment of endothelial progenitor cells (EPCs), capable for repairing a damaged endothelium, can be important in the vascular stent application. Therefore, we focused on the hypothesis that stromal cell-derived factor-1α (SDF-1α) acts as a key chemokine for the mobilization and recruitment of EPCs to the damaged endothelium lesion. In this study, the effect of SDF-1α released from a cobalt-chromium alloy (Co-Cr) plate, vascular stent material, was investigated on the recruitment of EPCs in vitro. Dopamine-conjugated heparin was synthesized to introduce heparin onto Co-Cr. Heparin-coated Co-Cr surfaces were examined by water contact angle and attenuated total reflectance-Fourier transform infrared (ATRFTIR) to prove successful coating of heparin. Finally, SDF-1α was bound to the coated heparin derivative. Amounts of loaded and released SDF-1α were measured by ELISA, and the recruited EPC by released SDF-1α was evaluated using two different migration assays. The quantity of SDF-1α bound to the heparin-modified surface increased in a concentration-dependent manner and SDF-1α was released over 28 days. Transwell migration assay revealed that soluble SDF-1α released from the heparin-coated Co-Cr induced significantly more EPC recruitment than bare Co-Cr and heparin-coated Co-Cr. More importantly, fibrin gel migration assay further demonstrated that EPCs evidently respond to heparin-based substrate with SDF-1α and this type of behaviors was surprisingly found at as low level as less 1 ng/day of SDF-1α. These results are strongly encouraging for further in vitro and in vivo studies. Open image in new window

Polymer-based drug-eluting stents (DESs) represented attractive application for the treatment of cardiovascular diseases; however, polymer coating has caused serious adverse responses to tissues such as chronic inflammation due to acidic by-products. Therefore, polymer-free DESs have recently emerged as promising candidates for the treatment; however, burst release of drug(s) from the surface limited its applications. In this study, we focused on delivery of therapeutic drug from polymer-free (or -less) DESs through surface modification using cobalt oxide nanowires (Co3O4 NWs) to improve and control the drug release. The results demonstrated that Co3O4 NWs could be simply fabricated on cobalt–chromium substrate by ammonia-evaporation-induced method. The Co3O4 NWs were uniformly arrayed with diameters of 50–100 nm and lengths of 10 µm. It was found that Co3O4 NWs were comparatively stable without any delamination or change of the morphology under in vitro long-term stability using circulating system. Sirolimus was used as a model drug for studying in vitro release behavior under physiological conditions. The sirolimus release behavior from flat cobalt–chromium showed an initial burst (over 90%) after one day. On the other hand, Co3O4 NWs presented a sustained sirolimus release rate for up to seven days. Similarly, the polymer-less specimens on Co3O4 NWs substrates sustained sirolimus release for a longer-period of time when compared to flat Co–Cr substrates. In summary, the current approach of using Co3O4 NWs-based substrates might have a great potential to sustain drug release for drug-eluting implants and medical devices including stents.

BACKGROUND: Kidney ischemia–reperfusion (IR) via laparotomy is a conventional method for kidney surgery in a mouse model. However, IR, an invasive procedure, can cause serious acute and chronic complications through apoptotic and inflammatory pathways. To avoid these adverse responses, a Non-IR and dorsal slit approach was designed for kidney surgery. METHODS: Animals were divided into three groups, 1) sham-operated control; 2) IR, Kidney IR via laparotomy; and 3) Non-IR, Non-IR and dorsal slit. The effects of Non-IR method on renal surgery outcomes were verified with respect to animal viability, renal function, apoptosis, inflammation, fibrosis, renal regeneration, and systemic response using histology, immunohistochemistry, real-time polymerase chain reaction, serum chemistry, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, and Masson’s trichrome staining. RESULTS: The Non-IR group showed 100% viability with mild elevation of serum blood urea nitrogen and creatinine values at day 1 after surgery, whereas the IR group showed 20% viability and lethal functional abnormality. Histologically, renal tubule epithelial cell injury was evident on day 1 in the IR group, and cellular apoptosis enhanced TUNEL-positive cell number and Fas/caspase-3 and KIM-1/NGAL expression. Inflammation and fibrosis were high in the IR group, with enhanced CD4/CD8-positive T cell infiltration, inflammatory cytokine secretion, and Masson’s trichrome stain-positive cell numbers. The Non-IR group showed a suitable microenvironment for renal regeneration with enhanced host cell migration, reduced immune cell influx, and increased expression of renal differentiation-related genes and anti-inflammatory cytokines. The local renal IR influenced distal organ apoptosis and inflammation by releasing circulating pro-inflammatory cytokines. CONCLUSION: The Non-IR and dorsal slit method for kidney surgery in a mouse model can be an alternative surgical approach for researchers without adverse reactions such as apoptosis, inflammation, fibrosis, functional impairment, and systemic reactions.

Biomedical devices have come a long way since they were first introduced as a medically interventional methodology in treating various types of diseases. Different techniques were employed to make the devices more biocompatible and promote tissue repair; such as chemical surface modifications, using novel materials as the bulk of a device, physical topological manipulations and so forth. One of the strategies that recently gained a lot of attention is the use of tissue-inspired biomaterials that are coated on the surface of biomedical devices via different coating techniques, such as the use of extracellular matrix (ECM) coatings, extracted cell membrane coatings, and so on. In this chapter, we will give a general overview of the different types of tissue-inspired coatings along with a summary of recent studies reported in this scientific arena.

The appropriate anti-adhesive effect of polymers on cells or tissues in the body is one of the essential requirements of maintaining health and protecting the body from trauma and foreign bodies. Regulating the anti-adhesive properties of biomedical polymers against cells has been considered a pivotal parameter in developing polymeric biomaterials for biomedical applications such as artificial blood vessels and cell encapsulation. Meanwhile, tissue adhesion barriers that can physically isolate wounds and thus effectively prevent the formation of tissue adhesion have been a hot topic in both research and industrial fields. This review describes the comprehensive knowledge and recent research efforts on polymers for anti-adhesion to both cells and tissues. The basic concepts and mechanisms for the design and performance of anti-adhesive polymers are introduced in terms of both cell and tissue. Polymer-based approaches for anti-adhesion to cells or tissues are then extensively discussed.

A drug-eluting stent (DES) is one of the commonly used treatment techniques in percutaneous coronary intervention (PCI). Sirolimus (SRL) has been widely used for DES as a drug for suppressing neointimal hyperplasia causing restenosis. Phytoncides (PTC) are compounds released from trees and plants, and their solutions contain monoterpenoids such as α-pinene, careen, and myrceen. Some studies have reported that these components exhibit antioxidant, antimicrobial, and anti-inflammatory activities. We hypothesized that PTC may become an alternative drug to SRL for DES, exhibiting alleviated side effects as compared to SRL. A PTC-incorporated stent was compared with an SRL-incorporated stent in terms of physicochemical, pharmacokinetic, and biological properties. In in vitro studies, the effects of each drug on cells were investigated. The results showed that both drugs exhibited similar cytotoxicity, anti-inflammation, and antiproliferation effects. However, these effects resulted from different mechanisms associated with cells, as seen in the immunofluorescence result. An in vivo assay showed that the lumen area was significantly larger and the neointimal area was significantly smaller in SRL- and PTC-loaded stents compared to a drug-unloaded stent. These results suggest that phytoncide can be a feasible alternative drug to SRL for advanced DES although more studies are needed.

Objectives/Hypothesis This study was conducted to determine whether a surface-modified tracheal T-tube can prevent tracheal stenosis in a rabbit model. Study Design Animal model study. Methods We designed surface-modified tracheal T-tubes in which silicone rubber was modified by coating it with hyaluronic acid (HA) or polyethylene glycol (PEG). Sixteen rabbits were divided into four insertion groups: normal, silicone tube, silicone tube coated with HA, and silicone tube coated with PEG. Surface-modified tubes were inserted into the tracheal lumen after a scraping injury on the inner tracheal mucosa around the preformed tracheostoma. Laryngoscopy was performed to evaluate formation of stenosis in the trachea. Histological examinations were performed to evaluate epithelial thickness, inflammatory response, and fibrosis. Results Endoscopic finding showed that the HA- and PEG-coated tube groups had less granulation tissue in the trachea than the noncoated tube group. Greater epithelialization was observed in the noncoated tube group than in the normal group. HA- and PEG-coated tube groups showed a tendency to decreasing epithelialization compared with the noncoated tube group. More inflammatory cells were observed in the noncoated tube group than in the normal group, and fewer inflammatory cells were observed in the HA- and PEG-coated tube groups than in the noncoated tube group. The noncoated tube group showed a greater area of fibrosis than the HA- and PEG-coated tube groups. Conclusions A surface-modified tracheal T-tube may have a favorable effect on reducing tracheal stenosis in a rabbit model. We suggest that local application of HA and PEG should be further researched for prevention of tracheal stenosis. Our rabbit model could be helpful in providing an additional scenario for evaluating new strategies to prevent tracheal stenosis. Level of Evidence NA Laryngoscope, 125:1465–1471, 2015

Cardiovascular diseases are considered as one of the serious diseases that leads to the death of millions of people all over the world. Stent implantation has been approved as an easy and promising way to treat cardiovascular diseases. However, in-stent restenosis and thrombosis remain serious problems after stent implantation. It was demonstrated in a large body of previously published literature that endothelium impairment represents a major factor for restenosis. This discovery became the driving force for many studies trying to achieve an optimized methodology for accelerated re-endothelialization to prevent restenosis. Thus, in this review, we summarize the different methodologies opted to achieve re-endothelialization, such as, but not limited to, manipulation of surface chemistry and surface topography.

Genetically-modified mesenchymal stem cells (GM-MSCs) have emerged as promising therapeutic tools for orthopedic degenerative diseases. GM-MSCs have been widely reported that they are able to increase bone and cartilage tissue regeneration not only by secreting transgene products such as growth factors in a long-term manner, also by inducing MSCs into tissue-specific cells. For example, MSCs modified with BMP-2 gene increased secretion of BMP-2 protein resulting in enhancement of bone regeneration, while MSCs with TGF-b gene did cartilage regeneration. In this review, we introduce several growth factors for gene delivery to MSCs and strategies for bone and cartilage tissue regeneration using GM-MSCs. Furthermore, we describe strategies for strengthening GM-MSCs to more intensively induce tissue regeneration by co-delivery system of multiple genes.

Vascular stenting has a great attention as a treatment for coronary arteries diseases as compared with percutaneous balloon angioplasty. In-stent restenosis and thrombosis are side effects resulting from using bare metal stent (BMS). Employing platelet therapy allowed to reduce the rate of thrombosis, however, the rate of restenosis remains a major problem. In 2002, drug-eluting stents (DESs) were introduced as an effort to reduce the restenosis. The commercially available DESs continue to suffer from coating defects that might lead to a series of adverse effects. Most importantly, multiple concerns remain regarding the polymer coating integrity on metal surfaces or the relation of polymer irregularities to long- term adverse events.

Combination chemotherapy using more than two therapeutic agents with different modes of action is a promising strategy that can be used to enhance the therapeutic efficacy of cancer treatment, even though it is a complicated treatment modality. The aim of this study was to investigate how a novel multidrug nanocarrier is effective for combination chemotherapy in vitro and, more specifically, whether combined agents with different modes of action and physicochemical properties show synergistic cytotoxicity with the use of this nanocarrier. A heparin-Pluronic (Hep-Pr) nanogel encapsulating both paclitaxel and DNase was shown to be efficient for intracellular delivery with respect to size, encapsulation efficiency, and intracellular uptake/fates. As a result of these properties, a Hep-Pr nanogel combined with paclitaxel and DNase exhibited a dose-dependent synergistic cytotoxicity compared to single drug and free-drug treatments, whose combination indices were 0.93 and 0.45 at higher concentrations (250 and 500 μg/mL). Therefore, Hep-Pr nanogels have the potential to deliver multitherapeutic agents with different characteristics and thereby enhance the therapeutic efficacy of combination cancer chemotherapy.

Durable and blood-compatible coating of metallic biomaterials remains a major issue in biomedical fields despite its long history of development. In this study, in situ forming, metal-adhesive heparin hydrogels were developed to coat metallic substrates to enhance blood compatibility. The hydrogels are composed of metal-adhesive and enzyme-reactive amphiphilic block copolymer (Tetronic-tyramine/dopamine; TTD) and enzyme-reactive heparin derivatives (heparin-tyramine or heparin-polyethylene glycol-tyramine), which are cross-linkable in situ via an enzyme reaction. The combinations of heparin and Tetronic formed hydrogels with relatively high mechanical strengths of 300–5000 Pa within several tens of seconds; this was also confirmed by observing a dried porous structure as coated on a metal surface. The introduction of dopamine to the hydrogel network enhanced the durability of the hydrogel layers coated on metal, such that more than 60% heparin remained for 7 days. Compared to bare metal surfaces, hydrogel-coated metal surfaces exhibited significantly enhanced blood compatibility. Reduced fibrinogen adsorption and platelet adhesion showed that blood compatibility was 3–5-fold-enhanced on coated hydrogel layers than on the bare metal surface. In conclusion, hydrogels containing heparin and dopamine prepared by enzyme reaction have the potential to be an alternative coating method for enhancing blood compatibility of metallic biomaterials.

Chronic kidney disease is now recognized as a major health problem, but current therapies including dialysis and renal replacement have many limitations. Consequently, biodegradable scaffolds to help repairing injured tissue are emerging as a promising approach in the field of kidney tissue engineering. Poly(lactic-co-glycolic acid) (PLGA) is a useful biomedical material, but its insufficient biocompatibility caused a reduction in cell behavior and function. In this work, we developed the kidney-derived extracellular matrix (ECM) incorporated PLGA scaffolds as a cell supporting material for kidney tissue regeneration. Biomimetic PLGA scaffolds (PLGA/ECM) with different ECM concentrations were prepared by an ice particle leaching method, and their physicochemical and mechanical properties were characterized through various analyses. The proliferation of renal cortical epithelial cells on the PLGA/ECM scaffolds increased with an increase in ECM concentrations (0.2, 1, 5, and 10%) in scaffolds. The PLGA scaffold containing 10% of ECM has been shown to be an effective matrix for the repair and reconstitution of glomerulus and blood vessels in partially nephrectomized mice in vivo, compared with only PLGA control. These results suggest that not only can the tissue-engineering techniques be an effective alternative method for treatment of kidney diseases, but also the ECM incorporated PLGA scaffolds could be promising materials for biomedical applications including tissue engineered scaffolds and biodegradable implants.

The clinical utility of a small-caliber vascular graft is still limited, owing to the occlusion of graft by thrombosis and restenosis. A small-caliber vascular graft (diameter, 2.5 mm) fabricated by electrospinning with a polyurethane (PU) elastomer (Pellethane) and biofunctionalized with heparin and two cell-adhesive peptides, GRGDS and YIGSR, was developed for the purpose of preventing the thrombosis and restenosis through antithrombogenic activities and endothelialization. The vascular grafts showed slightly reduced adhesion of platelets and significantly decreased adsorption of fibrinogen. In vitro studies demonstrated that peptide treatment on a vascular graft enhanced the attachment of human umbilical vein endothelial cells (HUVECs), and the presence of heparin and peptides on the graft significantly increased the proliferation of HUVECs. In vivo implantation of heparin/peptides coimmobilized graft (PU-PEG-Hep/G+Y) and PU (control) grafts was performed using an abdominal aorta rabbit model for 60 days followed by angiographic monitoring and explanting for histological analyses. The patency was significantly higher for the modified PU grafts (71.4%) compared to the PU grafts (46.2%) at 9 weeks after implantation. The nontreated PU grafts showed higher levels of α-SMA expression compared to the modified grafts, and for both samples, the proximal and distal regions expressed higher levels compared to the middle region of the grafts. Moreover, immobilization of heparin and peptides and adequate porous structure were found to play important roles in endothelialization and cellular infiltration. Our results strongly encourage that the development of small-caliber vascular grafts is feasible.

Stent implantation with balloon angioplasty is a widely used treatment for coronary artery diseases. Stents have been developed from bare metal stent (BMS) to advanced forms such as drug-eluting stent (DES). However, modern DES still causes thrombosis and/or in-stent restenosis as long-term outcomes. For effective prevention of these problems, we fabricated a dual functionalized stent using spatio-temporal coating, which has two different surfaces, as a novel type of DES. Hyaluronic acid conjugated with dopamine (HA-DA) was applied to a bare cobalt-chromium (CC) stent prior to abluminal coating of sirolimus (SRL)-in-polymer such as poly( d , l -lactide). The SRL-in-polymer (P+S) coated on the abluminal surface of the HA-DA modified stent showed highly stable coating layer and prevented the crack formation after ballooning. In the blood- and cyto-compatibility tests, HA-DA coating displayed suppressive effects on adhesion and activation of platelets and maintained the cell viability and proliferation of human coronary artery endothelial cells even under the existence of SRL. In in vivo study using porcine restenosis model, the neointimal area and inflammation score of the dual functionalized stent with HA-DA and P+S were significantly reduced than those of BMS. It is expected that this novel type of DES can be effectively applied to utilize diverse anti-proliferative drugs and bioactive polymers. Statement of Significance Stents have been developed from bare metal stent to advanced forms such as drug-eluting stents (DESs). However, even DESs can still cause in-stent restenosis as long-term outcomes. This paper demonstrated a novel DES using spatio-temporal coating by dopamine-mediated hyaluronic acid coating (HA-DA) before asymmetric coating of sirolimus-in-poly( d , l -lactide) (P+S). It showed stable coating surface and prevented crack formation after ballooning. HA-DA coating also had an inhibitive effect on adhesion of platelets and maintained cell viability of endothelial cells even under the existence of sirolimus. Additionally, in vivo neointima area and inflammation score of HA-DA/P+S stent significantly decreased than those of BMS. We expected that this novel type of DES can be effectively applied to introduce diverse anti-proliferative drugs and bioactive molecules.

The efficacy of three-dimensional (3D) culture on the proliferation and maturation of chondrocytes seeded into a hydrogel scaffold was assessed. Three types of hydrogel were prepared for the 3D culture of primary isolated chondrocytes. Chondrocyte proliferation was assessed using a live/dead viability/cytotoxicity assay and semiquantitative RT-PCR after 3D culture in hydrogel. Cylindrical defects in the center of rat xyphoids were used for the implantation of platelet-rich plasma (PRP)/hydrogel composites. Rats were killed at day 7 postoperatively and evaluated histochemically and immunohistologically. Xyphoid chondrocytes proliferated well with time in hydrogels. In the PRP-containing hydrogels, xyphoid defects displayed early formation of chondroid matrix with massive peripheral infiltration of spindle cells. These results were consistent with Safranin-O staining for proteoglycans and immunohistochemistry for type II collagen. Gene expression analyses in vitro revealed aggrecan, type II collagen, and ChM-1 and CB1 upregulation by PRP/hydrogel. PRP/hydrogel provided a suitable environment for hyaline cartilaginous regeneration, leading to anti-inflammation by significant increase of CB1 and inhibiting vascular ingrowth via considerable upregulation of ChM-1. The results provide a valuable reference for the clinical application of hydrogel scaffolds for hyaline cartilage regeneration, as well as the use of autologous PRP to improve cellular proliferation and maturation of xyphoid repair. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 100A:3099–3107, 2012.

In this study, in situ–forming quercetin-conjugated heparin hydrogels to be used to coat metal surfaces for blood compatibility were developed and characterized. Four units of quercetin and poly(ethylene glycol)–tyramine were conjugated per heparin for blood compatibility and hydrogel formation, respectively. The product, quercetin-conjugated heparin–poly(ethylene glycol)–tyramine, was cross-linked in situ via an enzymatic reaction using horseradish peroxidase and hydrogen peroxide to form a hydrogel. The physicochemical properties, such as the gelation time and swelling/degradation time as well as the release kinetics of quercetin, were controlled by changing the catalytic concentrations. The quercetin-conjugated heparin hydrogel, when adhered to a metal surface, enhanced blood compatibility and reduced platelet adhesion by 77%. The release of quercetin inhibited the proliferation of smooth muscle cells. The quercetin-conjugated heparin–poly(ethylene glycol)–tyramine hydrogel is a promising biomaterial with a stable-coated metal surface, with enhanced blood compatibility and antiproliferation effects.

Surface-modified poly(L-lactic acid) (PLLA) films and scaffolds were treated with plasma discharge in oxygen gas and subsequently subjected to in situ grafting of acrylic acid (AA) in order to increase the cell compatibility. The surface of AA-grafted PLLA was converted to hydroxyapatite (HA)-deposited PLLA in stimulated body fluid (SBF). After the samples were immersed in phosphate-buffered saline (PBS), fetal bovine serum (FBS), normal saline, or cell medium, the water contact angles were significantly reduced on the surface of HA-deposited PLLA. Chondrocyte and osteoblast showed a higher attachment and cell proliferation on HA-deposited surfaces and in particular, it was confirmed that chondrocyte was considerably influenced by HA. However, osteoblast showed better cell proliferation on the surfaces immersed in FBS, cell medium or HA-deposited surface. In addition, the cell proliferation in 3D scaffolds was much higher than that on film type, irrespective of chondrocyte and osteoblast. Therefore, such surface-modified PLLAs are expected to be useful as organic-inorganic hybrid scaffolds in the regeneration of cartilage and bone.

Three-dimensional scaffolds like hydrogels can be used for cell and drug delivery and have become a major research focus in tissue engineering. Presently, we investigated the regenerative potency of platelet-rich plasma (PRP) combined with a chondrocyte/hydrogel composite scaffold in the repair of articular cartilage defects using a rabbit model. Primary isolated joint chondrocytes from the trachlear groove of rabbit were cultured in hydrogels as follows; hydrogel (2900 Pa or 5900 Pa)+chondrocytes and hydrogel+chondrocytes+PRP for in vitro analysis and in vivo implantation. The 5900 Pa hydrogel markedly increased cellular viability and development in a time-dependent manner. Furthermore, the hydrogels attenuated the expression of SOX-9, aggrecan, and type II collagen. PRP-containing hydrogels produced an immediate increase in mRNA levels of cannabinoid receptor (CB)1 and CB2, compared with control and PRP-free hydrogels. Osteochondral defects were enhanced recovery with formation of cartilage and perichondrium in the 5900 Pa hydrogel+chondrocytes+PRP. Hydrogel may provide a suitable environment for proliferation and maturation of joint chondrocytes in relation to the gelation density and bioactive sources like PRP resulting in improvement for cartilage regeneration.

Rapid re-endothelialization of damaged vessel lining efficiently prevents restenosis and thrombosis and restores original vascular functions. In this study, we designed a novel metallic stent with a heparin-modified surface and used different methods, including 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and divinyl sulfone (DVS), to load growth factors. First we loaded heparin into a dopamine-conjugated hyaluronic acid (HA) coating to serve as a growth factor reservoir. In a second step, we took advantage of the heparin-binding domain of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) to gain advanced re-endothelialization capabilities. We demonstrated that DVS technique offered higher amount of growth factor loading. In vitro assessment also showed better capillary-like structure formation and localized gap junctions when DVS coating was employed. This study suggested that growth factor loaded stent modified by HA and heparin provided the advantage to rapid and tight restoration of endothelium.

Heparin has not been used as a macromolecule to prepare nanocarriers for drug delivery, even though it has advantageous structural features, such as a negatively charged structure and presence of specific binding domains of proteins. In this study, a nanogel of a Pluronic-conjugated heparin was prepared by direct dissolution to develop a versatile drug nanocarrier composed of heparin. The aqueous nanogel solution of the heparin-Pluronic (HP) conjugate, exhibited higher stability than the micelles and smaller hydrodynamic size than 100 nm. The drug encapsulation test demonstrated that the HP nanogel encapsulates efficiently both hydrophobic small molecules and proteins. The release profile of indomethacin (IMC) was almost zero-order without a burst due to the presence of heparin, which appears to be advantageous comparing to polymeric micelles. Circular dichroism (CD) and gel electrophoresis demonstrated that the stability of monoclonal antibodies (3D8 scFv) encapsulated into the HP nanogel had been maintained. Overall, the self-assembled HP nanogel may be a versatile and promising nanocarrier for a range of drugs in drug delivery applications.

Low molecular weight heparin (LH) has been reported to have anti-fibrotic and anti-cancer effects. To enhance the efficacy and minimize adverse effects of LH, a low molecular weight heparin-pluronic nanogel (LHP) was synthesized by conjugating carboxylated pluronic F127 to LH. The LHP reduced anti-coagulant activity by about 33% of the innate activity. Liver fibrosis was induced by the injection of 1% dimethylnitrosamine (DMN) in rats, and LH or LHP (1000 IU/kg body weight) was treated once daily for 4 weeks. LHP administration prevented DMN-mediated liver weight loss and decreased the values of aspartate transaminase, alanine transaminase, total bilirubin, and direct bilirubin. LHP markedly reduced the fibrotic area compared to LH. Also, LHP potently inhibited mRNA or protein expression of alpha-smooth muscle actin, collagen type I, matrix metalloproteinase-2, and tissue inhibitor of metalloproteinase-1 compared to LH, in DMN-induced liver fibrosis. In addition, LHP decreased the expression of transforming growth factor-β(1) (TGF-β(1)), p-Smad 2, and p-Smad 3, which are all important molecules of the TGF-β/Smad signaling pathway. The results support an LHP shows anti-fibrotic effect in the liver via inhibition of the TGF-β/Smad pathway as well as by the elimination of the extracellular matrix.

Injectable hydrogels are quite promising materials due to their potential to minimize invasive implantation and this provides versatile fitness irrespective of the damaged regions and facilitates the incorporation of bioactive agents or cells.In situ gel formation through stereocomplex formation is a promising candidate for injectable hydrogels. In this paper, a new series of enantiomeric, four-arm, PEG-PLA block copolymers and their stereocomplexed hydrogels were prepared by bulk ring-opening polymerization of D-lactide and L-lactide, respectively, with stannous octoate as a catalyst. The prepared polymers were characterized by1H nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FT IR) spectroscopy, gel permeation chromatography (GPC) and thermal gravitational analysis (TGA), confirming the tailored structure and chain lengths. The swelling and degradation behavior of the hydrogels formed from a selected copolymer series were observed in different concentrations. The degradation rate decreased with increasing polymer content in the solution. The rheological behavior indicated that the prepared hydrogel underwentin situ gelation and had favorable mechanical strength. In addition, its feasibility as an injectable scaffold was evaluated using a media dependence test for cell culture. A Tris solution was more favorable forin situ gel formation than PBS and DMEM solutions were. These results demonstrated thein situ formation of hydrogel through the construction of a stereocomplex with enantiomeric, 4-arm, PEG-PLA copolymers. Overall, enantiomeric, 4-arm, PEG-PLA copolymers are a new species of stereocomplexed hydrogels that are suitable for further research into injectable hydrogels.

Novel heparin-conjugated PLGA-PEG-PLGA hydrogels were prepared via Michael-type addition between thiolated heparin and PLGA-PEG-PLGA diacrylate. The thiolated heparin (HP-SH) was conjugated with thiolacid dihydrazide followed by reduction. The structure and the thiol determination of obtained HP-SH were characterized by 1H NMR and the Ellman method. Anticoagulant activity and pK a of the HP-SH were determined by aPTT test and UV absorbance measurement which were 79.3% and 10.5, respectively. The PLGA-PEG-PLGA diacrylate was synthesized by bulk ring-opening polymerization of D,L-lactide (DLLA) and glycolide (GA) with PEG and stannous 2-ethylhexanoate, followed by the acrylation of the terminal groups. HP—SH was then conjugated to PLGA-PEG-PLGA diacrylate by Michael addition. Phase diagrams of the hydrogels were obtained by vial tilting; the release of heparin from the hydrogels exhibited temperature dependent sol—gel transition behavior. These in situ-forming heparin-conjugated hydrogels are novel as injectable and tissue-compatible scaffold formation, thermo-sensitivity, and growth factor binding.

A RGD (Arg-Gly-Asp) conjugated chitosan hydrogel was used as a cell-supporting scaffold for articular cartilage regeneration. Thermosensitive chitosan-Pluronic (CP) has potential biomedical applications on account of its biocompatibility and injectability. A RGD-conjugated CP (RGD-CP) copolymer was prepared by coupling the carboxyl group in the peptide with the residual amine group in the CP copolymer. The chemical structure of RGD- CP was characterized by H NMR and FT IR. The concentration of conjugated RGD was quantified by amino acid analysis (AAA) and rheology of the RGD-CP hydrogel was investigated. The amount of bound RGD was 0.135 µg per 1 mg of CP copolymer. The viscoelastic parameters of RGD-CP hydrogel showed thermo-sensitivity and suit- able mechanical strength at body temperature for cell scaffolds (a > 100 kPa storage modulus). The viability of the bovine chondrocyte and the amount of synthesized glycosaminoglycans (GAGs) on the RGD-CP hydrogels were evaluated together with the alginate hydrogels as a control over a 14 day period. Both results showed that the RGD- CP hydrogel was superior to the alginate hydrogel. These results show that conjugating RGD to CP hydrogels improves cell viability and proliferation, including extra cellular matrix (ECM) expression. Therefore, RGD conju- gated CP hydrogels are quite suitable for a chondrocyte culture and have potential applications to the tissue engi- neering of articular cartilage tissue.

This work describes the development of heparinized polymeric micelle as a novel injectable carrier for the dual drug delivery that can simultaneously release basic fibroblast growth factor (bFGF) and indomethacin (IMC), which can promote the regeneration of damaged tissue and prevent the inflammatory response after implantation. Tetronic®–PCL–heparin for the preparation of heparinized polymeric micelle was synthesized by introducing PCL as a biodegradable linkage on Tetronic, following the conjugation of heparin. The mean diameter of the formed TCH micelle was around 114 nm and increases in the micelle size after single and dual drug loading were observed. Loading efficiencies of IMC and bFGF were 30.9% and 70.5%, respectively. In vitro dual drug release profiles from TCH micelles were investigated. IMC was more slowly released from dual drug-loaded micelle over 3 weeks as compared with single drug-loaded one. bFGF was released over 2 months in a controlled manner. Therefore, the release profile results support that TCH micelle could not only incorporate a hydrophobic drug into the core but also bind with bFGF to heparin that exists on its outer shell. The TCH micelle will have enhanced therapeutic effects on the target site which may be required the multi-function of drugs to use.

Antiplatelet and antithrombotic therapies are systematically considered to prevent restenosis following coronary stent implantation. Currently, patients receiving medicated stents are prescribed to orally take anticoagulants and antiplatelet drugs such as aspirin (ASP) and prasugrel (PRAS). Propolis (PROP) known as a natural organic compound was recently evaluated for its antiplatelet activity, antibiotics and immunomodulatory activities. In this study, antiplatelet drug-coated Co-Cr substrates were prepared with biodegradable poly(d,l-lactide) (PDLLA) containing ASP, PRA, or PROP using electrospray and the blood compatibility of the different substrates was investigated by measuring protein adsorption and platelet adhesion. In addition, the anti-inflammatory properties of the modified Co-Cr surfaces were assessed by measuring IL-8 and IL-6 expression levels in human endothelial cell cultures. Drug-coated surfaces were found to resist the adsorption of fibrinogen when compared to bare Co-Cr or PDLLA-coated Co-Cr. Interestingly, ASP- and PROP-containing substrates not only showed reduced adhesion of platelets and delayed coagulation time, but also drastically reduced the expression level of IL-8 and IL-6. Such results are supported that ASP- or PROP-coated Co-Cr can be potentially used as a stent material to mitigate early stage of restenosis. The developed coating materials might be an interesting alternative to systemic anticoagulant therapies prescribed after stent implantation.

Polyrotaxanes with both sulfonyl and carboxyl groups were synthesized and characterized for mimicking the anticoagulant activity of heparin. A polyrotaxane consisting of α-cyclodextrins (α-CDs) and poly(ethylene glycol) (PEG) was synthesized, and carboxyethylester (CEE) groups and taurine were successively conjugated with the polyrotaxane to obtain taurine-conjugated carboxyethylester-polyrotaxanes (TAU-CEE-PRxs). The number of α-CDs and the anionic groups could be varied by synthetic conditions. The structural factors of TAU-CEE-PRxs affecting anticoagulant activity were suggested as following: (i) relatively lower threading percentage of α-CDs, (ii) the ratio of anionic groups similar to heparin, and (iii) lower molecular weight of PEG. The TAU-CEE-PRx that sufficiently meet the mentioned requirements showed enhanced antithrombin III (AT III) activity, indicating that the TAU-CEE-PRx interacts with AT III and/or thrombin. From these results, it is suggested that the sliding and rotation of free α-CDs with anionic groups are related with enhancing anticoagulant activity.

This chapter describes some examples of heparin-conjugated nanointerfaces for biomedical applications in terms of both development and application. First, heparin-conjugated linear and star shaped poly(lactic acid) (PLA-Hep and sPLA-Hep) to improve blood compatibility and its related biocompatibility of degradable polymers were introduced. Second, a heparin-conjugated PM system that consists of Tetronic and poly(ɛ-caprolactone) (PCL) is described as an injectable vehicle for an effective long-term delivery of growth factors. Finally, the heparin-immobilized small intestinal submucosa (SIS) was investigated to observe the effect of heparin immobilization on blood compatibility, in vitro fibroblast attachment and in vivo calcification of SIS. All of these examples demonstrate that heparin-conjugated nanointerfaces might be a versatile and promising tool to achieve advanced biomaterials.

The strategy of growth factor delivery to specific sites for therapeutic applications has been considered an essential process in biomedical fields despite some obstacles, such as a non-controlled release with initial burst. This article focuses on particulate systems using heparin for the controlled delivery of heparin-binding growth factors (HBGFs), an emerging area in the tissue engineering field. Since heparin has been widely utilized for growth factor delivery due to its electrostatic nature and specific affinity with HBGFs, heparin-containing polymeric particulates can be utilized as functional carriers to deliver growth factors in a controlled manner. In particular, examples of the HBGF delivery systems containing heparin, perspectives and potential applications are described and discussed.

Injectable hydrogels have been studied for potential applications for articular cartilage regeneration. In this study, a thermosensitive chitosan-Pluronic (CP) hydrogel was designed as an injectable cell delivery carrier for cartilage regeneration. The CP conjugate was synthesized by grafting Pluronic onto chitosan using EDC/NHS chemistry. The sol-gel phase transition and mechanical properties of the CP hydrogel were examined by rheological experiments. The CP solution underwent a sol-gel transition around 25 degrees C at which the storage modulus (G') approaches 10(4)Pa, highlighting the potential of this material as an injectable scaffold for cartilage regeneration. The CP hydrogel was formed rapidly by increasing the temperature. The morphology of the dried CP hydrogel was observed by scanning electron microscopy. In vitro cell culture was performed using bovine chondrocytes. The proliferation of bovine chondrocytes and the amount of synthesized glycosaminoglycan increased for 28 days. These results suggested that the CP hydrogel has potential as an injectable cell delivery carrier for cartilage regeneration and could serve as a new biomaterial for tissue engineering.

Low efficiency and stability problems have been major issues in the formulation of engineered monoclonal antibodies (mAbs) for a variety of therapeutic uses, which may be severer for applying to encapsulation into nanoparticle (NP). In this study, the formulation and stabilizing conditions to encapsulate a potential mAb (3D8 scFv) into biodegradable poly(lactic-co-glycolic acid) (PLGA) NPs were investigated. And the effect of stabilizers on the stability of 3D8 scFv was investigated with the 3D8 scFv that was recovered from the primary emulsion in the double emulsion process. The conformational stability of the recovered 3D8 scFv was evaluated by circular dichroism (CD) and fluorescence spectroscopy. The DNA binding and hydrolyzing activities of the recovered 3D8 scFv were evaluated by enzyme-linked immunosorbent assay (ELISA) and agarose gel electrophoresis, respectively. The results conclude that mannitol was the most suitable stabilizer for retaining stability and activity of 3D8 scFv in the process of the PLGA NP preparation. Finally, obtained results suggest that this systematic process can provide efficient delivery system of 3D8 scFv as well as other potential mAbs or proteins for therapeutic uses, which is likely to be useful for intracellular delivery requiring sustained release.

Star-shaped PLA-heparin (sPLA-Hep) was prepared by coupling heparin to the star-shaped PLA (sPLA) reaction using carbonyldiimidazole (CDI) chemistry. Hydroxyl groups of sPLA were activated by CDI for the reaction with the remained amino-terminal groups of heparin. The surface heparin content of sPLA-Hep was measured to be 1.43 μg/cm2. sPLA-Hep-coated surface has shown higher hydrophilicity than control surface. The clotting time of sPLA-Hep measured by activated partial thromboplastin time (APTT) was significantly prolonged when compared with sPLA and linear PLA-Hep. sPLA-Hep surface demonstrated lower protein adsorption and platelet adhesion than control sPLA surface. In addition, fibroblast culture on the sPLA-Hep surface showed the enhanced cell spreading area compared with the sPLA surface. Obtained results suggest that the incorporation of heparin to sPLA is effective in curtailing the surface induced-thrombosis and in manipulating the cell interaction. sPLA-Hep could be applied as blood/tissue compatible biodegradable materials for implantable medical devices and tissue engineering. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 2008

For the prevention of coronary restenosis, estrogen was coupled onto a metallic stent and in vitro release of estrogen was investigated. Estrogen was introduced to the metal surface using a hydrolysable covalent bond for local sustained delivery of drug as follows: (i) the stainless steel (SS) surface was activated with silane by plasma polymerization, (ii) the activated surface (SS–Si surface) was treated with acrylic acid by plasma polymerization (SS–Si–AAc surface), and (iii) 17β-estradiol (E 2 ) was covalently linked to the carboxyl group on that surface (SS–Si–AAc–E 2 surface). The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and water contact angle measurement. The amount of E 2 was measured by UV–visible spectrophotometry and high performance liquid chromatography (HPLC). The in vitro release profile of E 2 demonstrated sustained release of E 2 in aqueous buffer. In summary, a novel method of immobilizing estrogen onto a metallic stent surface using plasma polymerization has been developed. The obtained results attest to the usefulness of the estrogen-releasing stent for preventing restenosis.