Functionally graded hydrogels with opposing biochemical cues for osteochondral tissue engineering

Osteochondral tissue (OC) repair remains a significant challenge in the field of musculoskeletal tissue engineering. OC tissue displays a gradient structure characterised by variations in both cell types and extracellular matrix components from cartilage to the subchondral bone. These functional gradients in the native tissue have been replicated to engineer osteochondral tissue in vitro. While diverse fabrication methods have been employed to create these microenvironments, emulating the natural gradients and effective regeneration of the tissue continues to present a significant challenge. In this study, we present the design and development of an interpenetrating (IPN) hydrogel with opposing dual biochemical gradients with the aim of regenerating the complete osteochondral unit. The gradients of biochemical cues were generated using an in-house built extrusion system in CMC-Silk IPN hydrogel having improved mechanical strength. Firstly, we fabricated a hydrogel that exhibits a smooth transition of sCMC and TGF-β1 (SCT gradient hydrogel) from the upper to the lower region of the IPN hydrogel, with the intent of regenerating the cartilage layer. Secondly, a hydrogel with a HAp gradient (HAp gradient hydrogel) from the lower to the upper region was fabricated to facilitate the regeneration of the subchondral bone layer. Subsequently, we developed a dual biochemical gradient hydrogel with the goal of regenerating the entire osteochondral unit. The fabricated hydrogel demonstrated a smooth transition of sCMC + TGF-β1 and HAp gradients in opposing directions, along with a blend of both the biochemical cues at the interface. The results showed that the hydrogels having biochemical cues corresponding to the three zones (i.e., cartilage, interface and bone) of dual biochemical gradient hydrogel led to differentiation of BMSCs towards their respective lineages, thereby demonstrating their efficacy in directing the fate of progenitor cells. The developed dual gradient hydrogel provided biochemical signals that have the potential to facilitate tissue growth and regeneration of the entire osteochondral tissue with a smooth transition from cartilage (soft) to bone (hard) tissues. In summary, our study provides a simple and innovative method for incorporating biochemical cues into hydrogels. This promising approach is translatable and has the potential to be extrapolated to other interface tissues. .

Engineering sulfated polysaccharides and silk fibroin based injectable IPN hydrogels with stiffening and growth factor presentation abilities for cartilage tissue engineering

The extracellular matrix (ECM) presents a framework for various biological cues and regulates homeostasis during both developing and mature stages of tissues. During development of cartilage, the ECM plays a critical role in endowing both biophysical and biochemical cues to the progenitor cells. Hence, designing microenvironments that recapitulate these biological cues as provided by the ECM during development may facilitate the engineering of cartilage tissue. In the present study, we fabricated an injectable interpenetrating hydrogel (IPN) system which serves as an artificial ECM and provides chondro-inductive niches for the differentiation of stem cells to chondrocytes. The hydrogel was designed to replicate the gradual stiffening (as a biophysical cue) and the presentation of growth factors (as a biochemical cue) as provided by the natural ECM of the tissue, thus exemplifying a biomimetic approach. This dynamic stiffening was achieved by incorporating silk fibroin, while the growth factor presentation was accomplished using sulfated-carboxymethyl cellulose. Silk fibroin and sulfated-carboxymethyl cellulose (s-CMC) were combined with tyraminated-carboxymethyl cellulose (t-CMC) and crosslinked using HRP/H2O2 to fabricate s-CMC/t-CMC/silk IPN hydrogels. Initially, the fabricated hydrogel imparted a soft microenvironment to promote chondrogenic differentiation, and with time it gradually stiffened to offer mechanical support to the joint. Additionally, the presence of s-CMC conferred the hydrogel with the property of sequestering cationic growth factors such as TGF-β and allowing their prolonged presentation to the cells. More importantly, TGF-β loaded in the developed hydrogel system remained active and induced chondrogenic differentiation of stem cells, resulting in the deposition of cartilage ECM components which was comparable to the hydrogels that were treated with TGF-β provided through media. Overall, the developed hydrogel system acts as a reservoir of the necessary biological cues for cartilage regeneration and simultaneously provides mechanical support for load-bearing tissues such as cartilage.

Polyhydroxybutyrate-based osteoinductive mineralized electrospun structures that mimic components and tissue interfaces of the osteon for bone tissue engineering

Scaffolds for bone tissue engineering should enable regeneration of bone tissues with its native hierarchically organized extracellular matrix (ECM) and multiple tissue interfaces. To achieve this, inspired by the structure and properties of bone osteon, we fabricated polyhydroxybutyrate (PHB)-based mineralized electrospun fibrous scaffolds. After studying multiple PHB-based fibers, we chose 7%PHB/1%Gelatin fibers (PG) to fabricate mineralized fibers that mimic mineralized collagen fibers in bone. The mineralized PG (mPG) surface had a rough, hydrophilic layer of low crystalline calcium phosphate which was biocompatible to bone marrow stromal cells (BMSCs), induced their proliferation and was osteoinductive. Subsequently, by modulating the electrospinning process, we fabricated mPG-based novel higher order fibrous scaffolds that mimic the macroscale geometries of osteons of bone ECM. Inspired by the aligned collagen fibers in bone lamellae, we fabricated mPG scaffolds with aligned fibers that could direct anisotropic elongation of mouse BMSC (mBMSCs). Further, we fabricated electrospun mPG-based osteoinductive tubular constructs which can mimic cylindrical bone components like osteons or lamellae or be used as long bone analogues based on their dimensions. Finally, to regenerate tissue interfaces in bone, we introduced a novel bi-layered scaffold-based approach. An electrospun bi-layered tubular construct that had PG in the outer layer and 7%PHB/0.5%Polypyrrole fibers (PPy) in the inner layer was fabricated. The bi-layered tubular construct underwent preferential surface mineralization only on its outer layer. This outer mineralized layer supported osteogenesis while the inner PPy layer could support neural cell growth. Thus, the bi-layered tubular construct may be used to regenerate haversian canal in the osteons which hosts nerve fibers. Overall, the study introduced novel techniques to fabricate biomimetic structures that can regenerate components of bone osteon and its multiple tissue interfaces. The study lays foundation for the fabrication of a modular scaffold that can regenerate bone with its hierarchical structure and complex tissue interfaces.

Directing ligament-mimetic bi-directional cell organization in scaffolds through zone-specific microarchitecture for ligament tissue engineering

Ligament tissues exhibit zone-specific anisotropic cell organization. The cells in ligament-proper are longitudinally oriented, whereas, the cells in epiligament are circumferentially oriented. Therefore, scaffolds developed to regenerate ligament tissues should possess adequate architectural features to govern ligament-mimetic bi-directional cell organization. The scaffold architectural features along with ligament-mimetic cell organization may ultimately yield neo-tissues with ligament-like extracellular matrix (ECM) structure and biomechanical properties. Towards this goal, we fabricated a silk/gelatin-based core-shell scaffold (csSG) with zone-specific anisotropic architectural features, wherein, the core of the scaffold possessed longitudinally aligned pores while the shell of the scaffold possessed parallel microgrooves that are aligned circumferentially around the surface of the scaffold. The ligament-mimetic architectural features significantly improved the mechanical properties of the scaffold. Moreover, architectural features of the csSG scaffold governed zone-specific anisotropic organization of cells. The cells in the core were longitudinally oriented as observed in the ligament-proper and the cells on the shell were circumferentially oriented as observed in epiligament. This bi-directional cell orientation partially mimicked the complex cellular network in native ligament tissue. Additionally, both the core and the shell individually supported fibrogenic differentiation of stem cells which further improved their potential for ligament tissue engineering. Further, the aligned pores of the core could govern unidirectional organization of ECM deposited by cells which is crucial for regenerating anisotropic tissues like ligaments. Finally, when implanted subcutaneously in mice, the scaffolds retained their anisotropic architecture for at least 2 weeks, were biocompatible, supported cell infiltration and governed anisotropic organization of cells and ECM. Taken together, the fabricated biomimetic csSG scaffold, through its zone-specific architectural features, could govern ligament-mimetic cellular and ECM organization which is ultimately expected to achieve regeneration of ligament tissues with native-like hierarchical structure and biomechanical properties. Consequently, this study introduces bi-directional structural parameters as design criteria for developing scaffolds for ligament tissue engineering.

Piperlongumine mediates amelioration of osteoarthritis via inhibition of chondrocyte senescence and inflammation in a goat ex vivo model

In osteoarthritis (OA), chondrocytes manifest senescence, which results in a vicious signaling loop that aids the progression of the disease. More specifically, inflammation-associated senescence is one of the major regulators of the initiation and progression of OA. Therefore, we targeted senescence through inflammation with a pharmacological approach for OA amelioration. In this study, we first confirmed the suitability of the IL1β-induced goat ex vivo OA model (emphasizing 3R's principle) for the screening of senotherapeutics, namely, ABT-263, ABT-737, and Piperlongumine (PL), wherein PL showed a positive outcome in the preliminary studies. Thereafter, we determined the cytocompatible concentrations of PL using live/dead staining. Further, treatment of ex vivo OA cartilage with PL exhibited a concentration-dependent increase in the retention of key cartilage matrix components. We then examined the effect of PL on chondrocyte senescence and observed a decreased expression of major senescence markers in the PL-treated groups. Interestingly, PL treatment reduced the expression of major downstream effectors of the chondrocyte senescence pathway in a concentration-dependent manner at both gene and protein levels. Moreover, IL1β-induced elevated levels of oxidative stress and DNA damage in cartilage explants were rescued by all the tested concentrations of PL. In addition, PL also reduced the expression of major inflammatory markers of OA in the goat ex vivo OA model. Finally, we proposed a model for the mechanism of action of PL in the treatment of OA. Overall, PL showed a promising outcome as a senotherapeutic for the amelioration of OA in the goat ex vivo OA model.

Targeting multiple disease hallmarks using a synergistic disease-modifying drug combination ameliorates osteoarthritis via inhibition of senescence and inflammation

AIMS

Osteoarthritis (OA), is a debilitating disease characterized by progressive cartilage degradation, synovial inflammation, and chondrocyte senescence. Various treatment agents independently targeting these hallmarks have been investigated. However, due to the complex multifaceted nature of OA, no disease-modifying osteoarthritis drugs are clinically available. In an attempt to overcome this, we developed a combinatorial approach and demonstrated the efficacy of TsC [Tissue inhibitor of metalloproteinase-3 (TIMP3) + sulfated carboxymethylcellulose (sCMC)] and piperlongumine (PL) combination for the amelioration of OA in a goat ex vivo OA model.

MAIN METHODS

The efficacy of the drug combination was evaluated using the goat ex vivo OA explant model and results were validated in clinically relevant human OA cartilage explants. The chondroprotective effects were evaluated in terms of reduced inflammation and cartilage matrix loss, reduction in chondrosenescence, and reduced oxidative stress.

KEY FINDINGS

A combination of TsC and PL (TsC-PL) significantly reduced inflammation, cartilage matrix loss, chondrosenescence, and oxidative stress in the goat ex vivo OA model and showed chondroprotective effects. Further, similar chondroprotective effects were observed in human OA cartilage. Additionally, the coefficient of drug interaction analysis indicated that the combination of TsC and PL had a synergistic effect in reducing matrix degrading proteases and inflammation (goat ex vivo OA model) and Reactive oxygen species (ROS) production (human OA cartilage).

SIGNIFICANCE

Combinatorial treatment with TsC and PL demonstrated potential disease-modifying effects for the treatment of osteoarthritis via inhibition of inflammation and senescence and supports the usage of treatment strategies targeting multiple pathological factors of OA simultaneously.

Converse modulation of Wnt/β-catenin signaling during expansion and differentiation phases of Infrapatellar fat pad-derived MSCs for improved engineering of hyaline cartilage

Mesenchymal stem cells (MSCs) are potential candidates in cell-based therapy for cartilage repair and regeneration. However, during chondrogenic differentiation, MSCs undergo undesirable hypertrophic maturation. This poses a risk of ossification in the neo-tissue formed that eventually impedes the clinical use of MSCs for cartilage repair. TGF-β is a potent growth factor used for chondrogenic differentiation of MSCs, however, its role in hypertrophy remains ambiguous. In the present work, we decipher that TGF-β activates Wnt/β-catenin signaling through SMAD3 and increases the propensity of Infrapatellar fat pad derived MSCs (IFP-MSCs) towards hypertrophy. Notably, inhibiting TGF-β induced Wnt/β-catenin signaling suppresses hypertrophic progression and enhances chondrogenic ability of IFP-MSCs in plasma hydrogels. Additionally, we demonstrate that activating Wnt signaling during expansion phase, promotes proliferation and reduces senescence, while improving stemness of IFP-MSCs. Thus, conversely modulating Wnt signaling in vitro during expansion and differentiation phases generates hyaline-like cartilage with minimal hypertrophy. Importantly, pre-treatment of IFP-MSCs encapsulated in plasma hydrogel with Wnt modulators followed by subcutaneous implantation in nude mice resulted in formation of a cartilage tissue with negligible calcification. Overall, this study provides technological advancement on targeting Wnt/β-catenin pathway in a 3D scaffold, while maintaining the standard chondro-induction protocol to overcome the challenges associated with the clinical use of MSCs to engineer hyaline cartilage.

Sulfated carboxymethylcellulose mediated enhancement of Timp3 efficacy synergistically attenuates osteoarthritis through inhibition of NFκB and JNK

Osteoarthritis (OA) is a prevalent degenerative joint condition with no effective disease modifying treatments. In this study, we aimed to address multiple OA hallmarks using a combination of pro-chondrogenic sulfated carboxymethylcellulose (sCMC) and anti-catabolic tissue inhibitor of metalloproteases 3 (Timp3) in relevant disease systems. Firstly, we chemically sulfated carboxymethylcellulose to impart a negative charge and improve the stability of cationic Timp3. The modified sCMC exhibited a molecular weight of 10 kDa and a degree of sulfation of ∼10 %. We further demonstrated that sulfation of CMC confers pro-chondrogenic characteristics. Subsequently, we demonstrated that the combination of sCMC and Timp3 effectively reduced key OA hallmarks, such as matrix degradation, inflammation, and protease expression, in a goat ex vivo OA model compared to individual treatments. We further demonstrated that the anti-OA effect of sCMC and Timp3 is mediated through the suppression of NFκB and JNK activation. To validate the clinical potential and mechanism of action, we conducted experiments on human OA explants. The combination treatment synergistically reduced the expression of MMP13 and NFκB in human OA explants. Overall, sCMC-mediated enhancement of Timp3 efficacy synergistically reduced OA-like traits and demonstrates the potential for OA amelioration.

Facile synthesis of multi-faceted, biomimetic and cross-protective nanoparticle-based vaccines for drug-resistant Shigella: a flexible platform technology

BACKGROUND

No commercial vaccines are available against drug-resistant Shigella due to serotype-specific/narrow-range of protection. Nanoparticle-based biomimetic vaccines involving stable, conserved, immunogenic proteins fabricated using facile chemistries can help formulate a translatable cross-protective Shigella vaccine. Such systems can also negate cold-chain transportation/storage thus overcoming challenges prevalent in various settings.

METHODS

We explored facile development of biomimetic poly (lactide-co-glycolide)/PLGA 50:50 based nanovaccines (NVs), encapsulating conserved stabilized antigen(s)/immunostimulant of S. dysenteriae 1 origin surface-modified using simple chemistries. All encapsulants (IpaC/IpaB/LPS) and nanoparticles (NPs)-bare and modified (NV), were thoroughly characterized. Effect of IpaC on cellular uptake of NPs was assessed in-vitro. Immunogenicity of the NVs was assessed in-vivo in BALB/c mice by intranasal immunization. Cross-protective efficacy was assessed by intraperitoneally challenging the immunized groups with a high dose of heterologous S. flexneri 2a and observing for visible diarrhea, weight loss and survival. Passive-protective ability of the simplest NV was assessed in the 5-day old progeny of vaccinated mice.

RESULTS

All the antigens and immunostimulant to be encapsulated were successfully purified and found to be stable both before and after encapsulation into NPs. The ~ 300 nm sized NPs with a zeta potential of ~ - 25 mV released ~ 60% antigen by 14th day suggesting an appropriate delivery kinetics. The NPs could be successfully surface-modified with IpaC and/or CpG DNA. In vitro experiments revealed that the presence of IpaC can significantly increase cellular uptake of NPs. All NVs were found to be cytocompatible and highly immunogenic. Antibodies in sera of NV-immunized mice could recognize heterologous Shigella. Immunized sera also showed high antibody and cytokine response. The immunized groups were protected from diarrhea and weight loss with ~ 70-80% survival upon heterologous Shigella challenge. The simplest NV showed ~ 88% survival in neonates.

CONCLUSIONS

Facile formulation of biomimetic NVs can result in significant cross-protection. Further, passive protection in neonates suggest that parental immunization could protect infants, the most vulnerable group in context of Shigella infection. Non-invasive route of vaccination can also lead to greater patient compliance making it amenable for mass-immunization. Overall, our work contributes towards a yet to be reported platform technology for facile development of cross-protective Shigella vaccines.

Stable Recombinant Invasion Plasmid Antigen C (IpaC)-Based Single Dose Nanovaccine for Shigellosis

Shigellosis, caused by the bacteria Shigella, is the leading cause of bacterial diarrhea and the second leading cause of diarrheal death among children under the age of five. Unfortunately, Shigella strains have acquired resistance to antibiotics, and a commercial vaccine is yet to be available. We have previously demonstrated that Shigella dysenteriae serotype 1 (Sd1)-based recombinant, stabilized, "invasion plasmid antigen C" (IpaC; 42 kDa) protein can induce robust immune responses in BALB/c mice against a challenge of a high dose of heterologous Shigella when immunized via three intranasal doses of IpaC without an adjuvant. In this work, in order to reduce the frequency of dosing and increase possible patient compliance, based on our previous screening, the minimum protective dose of stabilized IpaC (20 μg) was encapsulated in biodegradable polymeric poly(lactide-co-glycolide) nanoparticles (∼370 nm) and intranasally administered in BALB/c mice in a single dose. Interestingly, a single intranasal dose of the developed vaccine particles encapsulating only 20 μg of Sd1 IpaC led to a temporal increase in the antibody production with an improved cytokine response compared to free IpaC administered three times as described in our previous report. Upon intraperitoneal challenge with a high dose of heterologous Shigella flexneri 2a (common in circulation), the immunized animals were protected from diarrhea, lethargy, and weight loss with ∼67% survival, while all the control animals died by 36 h of the challenge. Overall, the developed nanovaccine could be explored as a potential noninvasive, cross-protective, single-dose, single-antigen Shigella vaccine amenable for scale-up and eventual mass immunization.

A human osteoarthritis mimicking goat cartilage explant-based disease model for drug screening

Although osteoarthritis (OA) is the most prevalent human joint disease with a large socioeconomic burden, it remains a neglected disease with no clinically approved disease modifying therapies. One of the key reasons for this is that the available disease models poorly recapitulate human OA-like traits, possibly because of the challenge of mimicking the disease in an ECM-rich cartilage tissue. In this study, we report the establishment and validation of a clinically relevant ex vivo OA model using IL1β-treated goat articular cartilage explants. Treatment with IL1β induced OA-like traits in goat cartilage explants and caused a shift in cartilage homeostasis towards enhanced catabolism, resulting in higher matrix degradation, overexpression of degradative and inflammatory mediators, and chondrocyte hypertrophy. We then validated the developed disease model for drug response using the drugs celecoxib, BMP7, and rapamycin, all of which demonstrated concentration-dependent disease amelioration in the model. Finally, we evaluated the translational relevance of the developed ex vivo OA model by comparing it with late-stage OA patient samples and observed a striking resemblance in terms of matrix degradation, expression of degradative enzymes, chondrocyte hypertrophy, and inflammation. Overall, the goat ex vivo OA model elicited a biological response to cytokine treatment that mirrors human OA-like traits and may reduce discordance between preclinical and clinical studies in OA drug development.

Bioinspired Injectable Hydrogels Dynamically Stiffen and Contract to Promote Mechanosensing-Mediated Chondrogenic Commitment of Stem Cells

Developing stiff and resilient injectable hydrogels that can mechanically support load-bearing joints while enabling chondrogenic differentiation of stem cells is a major challenge in the field of cartilage tissue engineering. In the present work, a triple-network injectable hydrogel system was engineered using Bombyx mori silk fibroin, carboxymethyl cellulose (CMC), and gelatin. The developed hydrogel demonstrated a simultaneous increase in both stiffness and contraction over time, thereby imparting a four-dimensional (4D) evolving niche to the cells. While resilience was provided by CMC, the dynamic alterations in the hydrogel matrix were attributed to the formation of β-sheets in silk. The engineered contraction facilitated condensation of cells that mimicked an important step during cartilage development. Subsequently, this led to downregulation of YAP signaling and enhanced chondrogenic commitment of stem cells. More importantly, the in vivo study showed that the ectopically regenerated cartilage was mature and closely resembled native articular cartilage. Overall, this strategy of engineering mechanotransduction that promotes chondrogenesis by contraction-mediated condensation is a promising and translatable approach for cartilage repair.

Development of a Self-Adjuvanting, Cross-Protective, Stable Intranasal Recombinant Vaccine for Shigellosis

With the acquirement of antibiotic resistance, Shigella has resulted in multiple epidemics of shigellosis, an infectious diarrheal disease, causing thousands of deaths per year. Unfortunately, there are no licensed vaccines, primarily due to low or serotype-specific immunogenicity. Thus, conserved subunit vaccines utilizing recombinant invasion plasmid antigens (Ipa) have been explored as cross-protective vaccine candidates. However, achieving cross-protection against Shigella dysenteriae 1, which caused multiple pandemics/epidemics in the recent past, has been difficult. Therefore, a rational approach to improve cross-protection in the preparation for a possible pandemic should involve conserved proteins from S. dysenteriae 1 (Sd1). IpaC is one such conserved immunogenic protein that is less explored as an independent vaccine due to its instability/aggregation. Therefore, to improve cross-protection and potential immunogenicity and to be prepared for a future epidemic/pandemic, herein, we stabilized recombinant Sd1 IpaC, expressed without its chaperone, using a previously reported stabilizing detergent (LDAO) in a modified protocol and assessed its vaccine potential without an adjuvant. The protein assembled into heterogeneous complex spherical structures in the presence of LDAO and showed improved stability at storage temperatures of -80, -20, 4, 25, and 37 °C while providing enhanced yield and concentration. The protein could also be stably lyophilized and reconstituted, increasing the convenience of transportation and storage. Upon intranasal administration in BALB/c mice, the stabilized-IpaC-immunized groups generated significant antibody response and were not only protected against a high intraperitoneal dose of homologous S. dysenteriae 1 but also showed 100% survival against heterologous Shigella flexneri 2a without an adjuvant, while the control animals showed visible diarrhea (bloody-Sd1 challenge), lethargy, and weight loss with 0% survival. Overall, this work demonstrates that stabilized IpaC can be explored as a minimalist, self-adjuvanting, cross-protective, intranasal, single-antigen Shigella vaccine.

Mesoporous Silica Nanoparticle-Based Combination of Niclosamide and Doxorubicin: Effect of Treatment Regimens on Breast Cancer Subtypes

Overexpressed Wnt/β-catenin signaling acts as a major cancer driver and plays an important role in the development of resistance against cancer chemotherapy. Therefore, the combinatorial approach of downregulating Wnt/β-catenin signaling along with using a chemotherapeutic agent may improve cancer therapy. However, systemic administration of free anticancer agents is nonspecific and poses serious side effects. Hence, the present study aimed at developing mesoporous silica nanoparticle (MSN)-based targeted combination therapy of a Wnt signaling inhibitor, niclosamide (Nic), and a conventional anticancer agent, doxorubicin (Dox). The results demonstrated the reproducible synthesis of highly stable and monodispersed sub-100 nm spherical shaped NPs. In vitro cytotoxicity studies demonstrated that the individual drug formulations caused concentration-dependent cytotoxicity to all of the three breast cancer subtypes, with higher concentrations being more cytotoxic. Further, sequential and concurrent combination of Nic-loaded MSNs with Dox-loaded MSNs was synergistic and caused significantly enhanced death in all breast cancer subtypes. Quantification of the combinatorial efficacy suggested that multiple combinatorial pairs were synergistic in all of the breast cancer types for both (sequential and concurrent) treatment regimens. However, the extent of synergism varied between the two treatment regimens in different clinical subtypes of breast cancer. Overall, the combination of Nic-loaded MSNs with Dox-loaded MSNs holds promise to be developed as an efficient therapeutic option for breast cancer irrespective of the clinical subtype in both sequential and concurrent treatment regimens.

Simultaneous amelioration of diabetic ocular complications in lens and retinal tissues using a non-invasive drug delivery system

Topically administered delivery systems for ophthalmic applications have been studied for the treatment of anterior or posterior eye diseases. However, simultaneous treatment of both anterior and posterior eye diseases has not been explored. In this study, we fabricated a topically administrable polymeric nanoparticle (NP)- based delivery system consisting of pluronic®F-68 shell and polycaprolactone core for the simultaneous treatment of both anterior and posterior eye diseases. These NPs were loaded with pyrrolidine dithiocarbamate (PDTC) or triamcinolone acetonide (TA) separately. The drug loading in NPs was optimized to initially achieve a moderate burst release of PDTC followed by slow and sustained release of both PDTC and TA. The resultant delivery system was studied for its in vivo efficacy in a diabetic retinopathy (DR) and cataract rat model. The results demonstrated that administration of PDTC NPs + TA NPs minimized oxidative stress in lens as evidenced by reduced levels of protein carbonyls and malondialdehyde, and, ameliorated DR complications in retina as evidenced by reduced expression of hypoxia inducible factor-1α along with a reduction in number of neovascular tufts and acellular capillaries. Therefore, delivery of PDTC and TA using PCL-PF68 NPs could be a useful approach for simultaneous treatment of diabetic cataract and DR.

A non-invasive nanoparticle-based sustained dual-drug delivery system as an eyedrop for endophthalmitis

Endophthalmitis is an infectious disease that affects the entire eye spreading to the internal retinal layers and the vitreous and causes severe sight-threatening conditions. Current treatment strategies rely on intraocular injections of antibiotics that are invasive, may lead to procedural complications and, ultimately, blindness. In this study, we developed a non-invasive strategy as an eyedrop containing nanoparticle-based dual-drug delivery system in which the hydrophobic poly-L-lactide core was loaded with azithromycin or triamcinolone acetonide, and the hydrophilic shell was made of chitosan. The developed nanoparticles were ~200-250 nm in size, spherical in shape, moderately hydrophilic, lysozyme tolerant, cytocompatible, and hemocompatible. Application of these chitosan-coated nanoparticles as eye drops to C57BL/6 mice showed higher bioavailability in choroid and retina when compared to the uncoated nanoparticles. The delivery system showed sustained release of drug for 300 h and exhibited antimicrobial effects against Gram-positive and Gram-negative bacteria and anti-inflammatory effects on activated microglial cells. Interestingly, the combination of the nanoparticles loaded with azithromycin and the nanoparticles loaded with triamcinolone acetonide acted synergistically as compared to either of the nanoparticles/drugs alone. Overall, the developed dual-drug delivery system is non-invasive, has antimicrobial and anti-inflammatory effects, and shows potential as an eye drop formulation against endophthalmitis.

A Synergistic Combination of Niclosamide and Doxorubicin as an Efficacious Therapy for All Clinical Subtypes of Breast Cancer

Simple Summary

Chemotherapy is the gold standard treatment option for metastatic cancers. However, the efficacy of chemotherapy is limited due to the development of resistance. The aberrantly expressed Wnt/β-catenin signaling pathway acts as one of the major cancer drivers that also causes the development of resistance. Therefore, in this study, we explored the combinatorial approach of downregulating the Wnt/β-catenin pathway along with using a chemotherapeutic agent as a strategy to overcome drug resistance and improve cancer therapy. We evaluated the combinatorial efficacy of Niclosamide (an antihelminthic repurposed as a Wnt signaling inhibitor) and Doxorubicin (first-line treatment for multiple cancers in the clinic) against breast cancer. The combination showed synergistically enhanced death of all three clinical subtypes of breast cancer cells in both the sequential and concurrent treatment regimens and holds the potential to be developed as an efficient therapeutic option for breast cancer irrespective of its clinical subtype.

Abstract

Drug resistance is one of the major hurdles in the success of cancer chemotherapy. Notably, aberrantly expressed Wnt/β-catenin signaling plays a major role in the initiation and maintenance of oncogenesis along with development of chemoresistance. Therefore, the combinatorial approach of targeting Wnt/β-catenin pathway along with using a chemotherapeutic agent seems to be a promising strategy to improve cancer therapy. In the present study, we evaluated the combination of niclosamide (Nic), an FDA-approved antihelminthic drug repurposed as a Wnt signaling inhibitor, and doxorubicin (Dox), a conventional anticancer agent, in all clinical subtypes of breast cancer viz. triple negative breast cancer, HER2 positive breast cancer, and hormone receptor positive breast cancer. The results demonstrated that the combination induced apoptosis and caused synergistically enhanced death of all breast cancer cell types at multiple combinatorial concentrations using both the sequential and concurrent treatment regimens. Mechanistically, downregulation of Wnt/β-catenin signaling and cell cycle arrest at G0/G1 phase by Nic and increase in reactive oxygen species by both Nic and Dox along with the inherent cytotoxicity of Dox mediated the synergism between the two drugs in both the treatment regimens. Overall, the combination of Nic and Dox holds promise to be developed as an efficient therapeutic option for breast cancer irrespective of its clinical subtype.

Sulfated carboxymethylcellulose conjugated electrospun fibers as a growth factor presenting system for tissue engineering

Inspired by the natural electrostatic interaction of cationic growth factors with anionic sulfated glycosaminoglycans in the extracellular matrix, we developed electrospun poly(hydroxybutyrate)/gelatin (PG) fibers conjugated with anionic sulfated carboxymethylcellulose (sCMC) to enable growth factor immobilization via electrostatic interaction for tissue engineering. The fibrous scaffold bound cationic molecules, was cytocompatible and exhibited a remarkable morphological and functional stability. Transforming growth factor-β1 immobilized on the sCMC conjugated fibers was retained for at least 4 weeks with negligible release (3%). Immobilized fibroblast growth factor-2 and connective tissue growth factor were bioactive and induced proliferation and fibrogenic differentiation of infrapatellar fat pad derived mesenchymal stem cells respectively with efficiency similar to or better than free growth factors. Taken together, our studies demonstrate that sCMC conjugated PG fibers can immobilize and retain function of cationic growth factors and hence show potential for use in various tissue engineering applications.

In vivo cartilage regeneration in a multi-layered articular cartilage architecture mimicking scaffold

AIMS

Extracellular matrix (ECM) and its architecture have a vital role in articular cartilage (AC) structure and function. We hypothesized that a multi-layered chitosan-gelatin (CG) scaffold that resembles ECM, as well as native collagen architecture of AC, will achieve superior chondrogenesis and AC regeneration. We also compared its in vitro and in vivo outcomes with randomly aligned CG scaffold.

METHODS

Rabbit bone marrow mesenchymal stem cells (MSCs) were differentiated into the chondrogenic lineage on scaffolds. Quality of in vitro regenerated cartilage was assessed by cell viability, growth, matrix synthesis, and differentiation. Bilateral osteochondral defects were created in 15 four-month-old male New Zealand white rabbits and segregated into three treatment groups with five in each. The groups were: 1) untreated and allogeneic chondrocytes; 2) multi-layered scaffold with and without cells; and 3) randomly aligned scaffold with and without cells. After four months of follow-up, the outcome was assessed using histology and immunostaining.

RESULTS

In vitro testing showed that the secreted ECM oriented itself along the fibre in multi-layered scaffolds. Both types of CG scaffolds supported cell viability, growth, and matrix synthesis. In vitro chondrogenesis on scaffold showed an around 400-fold increase in collagen type 2 (COL2A1) expression in both CG scaffolds, but the total glycosaminoglycan (GAG)/DNA deposition was 1.39-fold higher in the multi-layered scaffold than the randomly aligned scaffold. In vivo cartilage formation occurred in both multi-layered and randomly aligned scaffolds treated with and without cells, and was shown to be of hyaline phenotype on immunostaining. The defects treated with multi-layered + cells, however, showed significantly thicker cartilage formation than the randomly aligned scaffold.

CONCLUSION

We demonstrated that MSCs loaded CG scaffold with multi-layered zonal architecture promoted superior hyaline AC regeneration.Cite this article: Bone Joint Res 2020;9(9):601-612.

Role of Physicochemical Properties of Protein in Modulating the Nanoparticle-Bio Interface

Nanoparticles, on exposure to the biological milieu, tend to interact with macromolecules to form a biomolecular corona. The biomolecular corona confers a unique biological identity to nanoparticles, and its protein composition plays a deterministic role in the biological fate of nanoparticles. The physiological behavior of proteins stems from their physicochemical properties, including surface charge, hydrophobicity, and structural stability. However, there is insufficient understanding about the role of physicochemical properties of proteins in biomolecular corona formation. We hypothesized that the physicochemical properties of proteins would influence their interaction with nanoparticles and have a deterministic effect on nanoparticle-cell interactions. To test our hypothesis, we used model proteins from different structural classes to understand the effect of secondary structure elements of proteins on the nanoparticle-protein interface. Further, we modified the surface of proteins to study the role of protein surface characteristics in governing the nanoparticle-protein interface. For this study, we used mesoporous silica nanoparticles as a model nanoparticle system. We observed that the surface charge of proteins governs the nature of the primary interaction and the extent of subsequent secondary interactions causing structural rearrangements of the protein. We also observed that the secondary structural contents of proteins significantly affected both the extent of secondary interactions at the nanoparticle-protein interface and the dispersion state of the nanoparticle-protein complex. Further, we studied the interactions of different protein-coated nanoparticles with different cells (fibroblast, carcinoma, and macrophage). We observed that different cells internalized the nanoparticle-protein complex as a function of secondary structural components of the protein. The type of model protein had a significant effect on their internalization by macrophages. Overall, we observed that the physicochemical characteristics of proteins had a significant role in modulating the nanoparticle-bio-interface at the level of both biomolecular corona formation and nanoparticle internalization by cells.

Polycaprolactone as biomaterial for bone scaffolds: Review of literature

Bone tissue engineering using polymer based scaffolds have been studied a lot in last decades. Considering the qualities of all the polymers desired to be used as scaffolds, Polycaprolactone (PCL) polyester apart from being biocompatible and biodegradable qualifies to an appreciable level due its easy availability, cost efficacy and suitability for modification. Its adjustable physio-chemical state, biological properties and mechanical strength renders it to withstand physical, chemical and mechanical, insults without significant loss of its properties. This review aims to critically analyse the efficacy of PCL as a biomaterial for bone scaffolds.

A non-invasive nanoparticle mediated delivery of triamcinolone acetonide ameliorates diabetic retinopathy in rats

Diabetic retinopathy (DR) is a multifactorial manifestation associated with microvascular complications and is the fourth leading cause of visual impairment and blindness world-wide. Current day treatment of DR relies heavily on invasive techniques such as intravitreal injections of therapeutic agents. Unfortunately, intravitreal injections are associated with various complications such as intraocular bleeding, endophthalmitis, pain and discomfort resulting in poor patient compliance. To date, there has been no non-invasive drug delivery system reported for DR treatment. To address this, we developed a core-shell nanoparticle-based delivery system consisting of a hydrophobic polycaprolactone core and a hydrophilic Pluronic® F68 shell, loaded with triamcinolone acetonide and evaluated its efficacy in a DR rat model. After being administered as eye drops, the drug loaded nanoparticles significantly improved structural (retinal thickness and vascular health) and functional activity (rod and cone function) of retina as compared to DR controls that were treated with the drug alone or placebo nanoparticles. Furthermore, drug loaded nanoparticles reduced retinal inflammation as evidenced by a decrease in NF-κB, ICAM-1 and TNFα expression after 20 days of treatment. Similarly, a reduction in glial cell hyperplasia as evidenced by reduced GFAP expression, and a decrease in microvascular complications as evidenced by a decrease in VEGF secretion and microvascular tuft formation were observed in rat retinas after 40 days of treatment. The combined reduction in retinal inflammation and vascular abnormalities, both hallmarks of DR, demonstrates the potential of the nanoparticulate delivery system for use as a topical formulation for treating DR.

Co-culture of infrapatellar fat pad-derived mesenchymal stromal cells and articular chondrocytes in plasma clot for cartilage tissue engineering

BACKGROUND

Cell source plays a deterministic role in defining the outcome of a cell-based cartilage regenerative therapy and its clinical translational ability. Recent efforts in the direction of co-culture of two or more cell types attempt to combine the advantages of constituent cell types and negate their demerits.

METHODS

We examined the potential of co-culture of infrapatellar fat pad-derived mesenchymal stromal cells (IFP MSCs) and articular chondrocytes (ACs) in plasma clots in terms of their ratios and culture formats for cartilage tissue engineering.

RESULTS AND DISCUSSION

It was observed that IFP MSCs and ACs interact positively to produce a better quality hyaline cartilage-like matrix. While a supra-additive deposition of sulfated Glycosaminoglycans (sGAG), collagen type II, aggrecan and link protein was observed, deposition of collagen type I and X was sub-additive. (Immuno)-histologically similar cartilage was generated in vitro in IFP MSC:AC ratio of 50:50 and pure AC groups thus yielding a hyaline cartilage with 50% reduced requirement of ACs. Subsequently, we investigated if this response could be improved further by enabling better cell-cell interactions using scaffold-free systems such as self-assembled cartilage or by encapsulating cellular micro-aggregates in plasma clot. However, it was inferred that while self-assembly may have enabled better cell-cell interaction, poor cell survival negated its overall beneficial role, whereas the micro-aggregate group demonstrated highly heterogeneous matrix deposition within the construct, thus diminishing its translational utility. Overall, it was concluded that co-culture of IFP MSCs and ACs at a ratio of 50:50 within plasma clots demonstrated potential for cell-based cartilage regenerative therapy.

Pericellular plasma clot negates the influence of scaffold stiffness on chondrogenic differentiation

Matrix stiffness is known to play a pivotal role in cellular differentiation. Studies have shown that soft scaffolds (<2-3kPa) promote cellular aggregation and chondrogenesis, whereas, stiffer ones (>10kPa) show poor chondrogenesis in vitro. In this work we investigated if fibrin matrix from clotted blood can act as a soft surrogate which nullifies the influence of the underlying stiff scaffold, thus promoting chondrogenesis irrespective of bulk scale scaffold stiffness. For this we performed in vitro chondrogenesis on soft (∼1.5kPa) and stiff (∼40kPa) gelatin scaffolds in the presence and absence of pericellular plasma clot. Our results demonstrated that in absence of pericellular plasma clot, chondrocytes showed efficient condensation and cartilaginous matrix secretion only on soft scaffolds, whereas, in presence of pericellular plasma clot, cell rounding and cartilaginous matrix secretion was observed in both soft and stiff scaffolds. More specifically, significantly higher collagen II, chondroitin sulfate and aggrecan deposition was observed in soft scaffolds, and soft and stiff scaffolds with pericellular plasma clot as compared to stiff scaffolds without pericellular plasma clot. Moreover, collagen type I, a fibrocartilage/bone marker was significantly higher only in stiff scaffolds without plasma clot. Therefore, it can be concluded that chondrocytes surrounded by a soft fibrin network were unable to sense the stiffness of the underlying scaffold/substrate and hence facilitate chondrogenesis even on stiff scaffolds. This understanding can have significant implications in the design of scaffolds for cartilage tissue engineering.

STATEMENT OF SIGNIFICANCE

Cell fate is influenced by the mechanical properties of cell culture substrates. Outside the body, cartilage progenitor cells express significant amounts of cartilage-specific markers on soft scaffolds but not on stiff scaffolds. However, when implanted in joints, stiff scaffolds show equivalent expression of markers as seen in soft scaffolds. This disparity in existing literature prompted our study. Our results suggest that encapsulation of cells in a soft plasma clot, present in any surgical intervention, prevents their perception of stiffness of the underlying scaffold, and hence the ability to distinguish between soft and stiff scaffolds vanishes. This finding would aid the design of new scaffolds that elicit cartilage-like biochemical properties while simultaneously being mechanically comparable to cartilage tissue.

Physicochemical properties of core-shell type nanoparticles govern their spatiotemporal biodistribution in the eye

Due to the inherent barrier properties of eye tissues, a major challenge in treating eye diseases is to provide a therapeutic agent to the desired tissue in quantities and durations that are favorable. This study aimed at understanding the influence of physicochemical properties of nanoparticles on their spatiotemporal biodistribution in mouse eye. For this, core-shell nanoparticles with different properties were designed by varying either core or shell and administered as eye-drops to mice. The results demonstrated that all nanoparticles irrespective of type of core or shell followed the conjunctival-scleral pathway. The bioavailability of cores followed the order polylactide-co-glycolide≥polylactide≥polycaprolactone for all tissues and time-points. The bioavailability for all shell types was greater in conjunctiva, sclera, choroid and retina when compared to other eye tissues. Therefore, modulating physicochemical properties of nanoparticles can be used as a design strategy to devise drug carriers that target specific tissues of the eye.

A simple method for fabrication of electrospun fibers with controlled degree of alignment having potential for nerve regeneration applications

In peripheral nerve injuries where direct suturing of nerve endings is not feasible, nerve regeneration has been facilitated through the use of artificially aligned fibrous scaffolds that provide directional growth of neurons to bridge the gap. The degree of fiber alignment is crucial and can impact the directionality of cells in a fibrous scaffold. While there have been multiple approaches that have been used for controlling fiber alignment, however, they have been associated with a compromised control on other properties, such as diameter, morphology, curvature, and topology of fibers. Therefore, the present study demonstrates a modified electrospinning set-up, that enabled fabrication of electrospun fibers with controlled degree of alignment from non-aligned (NA), moderately aligned (MA, 75%) to highly aligned (HA, 95%) sub-micron fibers while keeping other physical properties unchanged. The results demonstrate that the aligned fibers (MA and HA) facilitated directional growth of human astrocytoma cells (U373), wherein the aspect ratio of cells was found to increase with an increase in degree of fibers alignment. In contrast to NA and MA fibers, the HA fibers showed improved contact guidance to U373 cells that was demonstrated by a significantly higher cell aspect ratio and nuclear aspect ratio. In conclusion, the present study demonstrated a modified electrospinning setup to fabricate differentially aligned fibrous scaffolds with the HA fibers showing potential for use in neural tissue engineering.

Poly(d,l-lactide-co-glycolide)-chitosan composite particles for the treatment of lung cancer

Tumor heterogeneity makes combination chemotherapy one of the preferred modes of treatment regimens. In this work, sequential exposure of two anticancer agents, paclitaxel (Tx) followed by topotecan (TPT), was shown to have a synergistic effect on non-small cell lung cancer (NSCLC) cell line, NCI-H460. In order to improve patient compliance, the aforementioned concept was translated into a drug delivery system comprising of poly(d,l-lactide-co-glycolide) (PLGA)-chitosan composite particles. TPT-containing chitosan micro-/nanoparticles were prepared by the facile technique of electrospraying and encapsulated within PLGA microparticles using emulsion-solvent evaporation technique for delayed release of TPT. The formulation containing Tx- and TPT-loaded composite particles demonstrated synergism when exposed to NCI-H460 cellular aggregates (tumoroids) generated in vitro. Overall, the results of this study demonstrated the potential of the formulation containing Tx and PLGA-chitosan (TPT-loaded) composite particles for the treatment of lung cancer.

Growth factor-delivery systems for tissue engineering: a materials perspective

The transplantation of organs, their surgical reconstruction or implantation of synthetic devices that can perform the function of organs, are the currently available methods for treating loss of tissue/organs in humans. However, the limitations associated with these techniques have led to the development of tissue engineering. One of the primary goals of tissue engineering is to provide growth factor delivery systems that can induce desired cell responses both in vitro and in vivo, in order to cause accelerated tissue regeneration. To make growth factors a more therapeutically viable alternative for the treatment of chronic degenerative diseases, a wide range of natural and synthetic materials have been employed as vehicles for their controlled delivery. The choice of material and design of the carrier device influence the mode of immobilization of growth factors on the scaffolds and their local/systemic administration. From a tissue engineer's perspective, materials could be used for designing scaffolds as well as for delivering single or multiple growth factors. Therefore, this review discusses growth factor delivery systems, with particular reference to carrier-based growth factor delivery systems with a focus on materials.

Combination of single walled carbon nanotubes/graphene oxide with paclitaxel: a reactive oxygen species mediated synergism for treatment of lung cancer

Heterogeneity in tumors has led to the development of combination therapies that enable enhanced cell death. Previously explored combination therapies mostly involved the use of bioactive molecules. In this work, we explored a non-conventional strategy of using carbon nanostructures (CNs) [single walled carbon nanotube (SWNT) and graphene oxide (GO)] for potentiating the efficacy of a bioactive molecule [paclitaxel (Tx)] for the treatment of lung cancer. The results demonstrated enhanced cell death following combination treatment of SWNT/GO and Tx indicating a synergistic effect. In addition, synergism was abrogated in the presence of an anti-oxidant, N-acetyl cysteine (NAC), and was therefore shown to be reactive oxygen species (ROS) dependent. It was further demonstrated using bromodeoxyuridine (BrdU) incorporation assay that treatment with CNs was associated with enhanced mitogen associated protein kinase (MAPK) activation that was ROS mediated. Hence, these results for the first time demonstrated the potential of SWNT/GO as co-therapeutic agents with Tx for the treatment of lung cancer.

Mathematical model of mechanical behavior of micro/nanofibrous materials designed for extracellular matrix substitutes

Electrospun micro/nanofibrous biomaterials are widely used as extracellular matrix substitutes in tissue engineering applications because of their structural and mechanical properties. To explore the influence of microstructure on the mechanical behavior of fibrous material, a mathematical model of the fiber system was developed. The model describes the microstructural properties of a fibrous matrix using a probability density function, and enables study of their mechanical properties. The results from the mathematical model were validated by qualitative comparison with the experimental results of mechanical testing of polystyrene electrospun nanofibrous materials. The analyses show a trend of three-phase load-displacement behavior. Initially, as an increasing number of fibers are recruited for load bearing, the load-displacement curve has a 'J'-shaped toe region, which is followed by a nearly linear load-displacement curve, in which the number of load-bearing fibers remains nearly steady. Finally, there is a phase when the load-displacement curve descends, indicating failure of the material. The increase in flexibility of the fibrous material makes it stronger, but the randomness of fiber orientation makes the fibrous structure more flexible at the cost of lower strength. The measured mechanical properties of a fibrous matrix were also observed to be dependent on sample size. Therefore, the analyses establish a clear link between the structure and strength of fibrous materials for optimized design and fabrication of fibrous biomaterials with targeted use in tissue engineering, regenerative medicine and drug delivery. The model also establishes a need for standardization of experimental protocols for mechanical characterization of fibrous materials for consistency.

A one-step electrospray-based technique for modulating morphology and surface properties of poly(lactide-co-glycolide) microparticles using Pluronics®

The influence of morphology and surface properties on the therapeutic efficacy of degradable polymeric microparticles has not been well understood. One of the primary reasons for this is the limited ability to fabricate microparticles with controlled morphology and surface properties. Here, we report the electrospraying of blends of Pluronic^® with poly(lactide-co-glycolide) (PLGA) as a novel, one-step approach for the simultaneous modulation of morphology and surface properties of PLGA microparticles. Blending with Pluronic^® altered the morphology from doughnut-shaped to smooth, spherical-shaped microparticles, and variation in the type of Pluronic^® systematically modulated the surface properties of the microparticles. Hence, blending with Pluronic^® can be a facile technique for the modulation of morphology and surface properties of electrosprayed PLGA microparticles.

Recapitulating tumour microenvironment in chitosan-gelatin three-dimensional scaffolds: an improved in vitro tumour model

Owing to the reduced co-relationship between conventional flat Petri dish culture (two-dimensional) and the tumour microenvironment, there has been a shift towards three-dimensional culture systems that show an improved analogy to the same. In this work, an extracellular matrix (ECM)-mimicking three-dimensional scaffold based on chitosan and gelatin was fabricated and explored for its potential as a tumour model for lung cancer. It was demonstrated that the chitosan-gelatin (CG) scaffolds supported the formation of tumoroids that were similar to tumours grown in vivo for factors involved in tumour-cell-ECM interaction, invasion and metastasis, and response to anti-cancer drugs. On the other hand, the two-dimensional Petri dish surfaces did not demonstrate gene-expression profiles similar to tumours grown in vivo. Further, the three-dimensional CG scaffolds supported the formation of tumoroids, using other types of cancer cells such as breast, cervix and bone, indicating a possible wider potential for in vitro tumoroid generation. Overall, the results demonstrated that CG scaffolds can be an improved in vitro tool to study cancer progression and drug screening for solid tumours.

Structural and functional characterization of proteins adsorbed on hydrophilized polylactide-co-glycolide microfibers

Background:

Hydrophobic biopolymers such as polylactide-co-glycolide (PLGA, 85:15) have been extensively explored as scaffolding materials for tissue engineering applications. More recently, electrospun microfiber-based and nanofiber-based scaffolds of PLGA have received increased attention because they act as physical mimics of the fibrillar extracellular matrix. However, the hydrophobicity of the PLGA microfiber surface can limit its use in biomedical applications. Therefore, in a previous study, we fabricated Pluronic^® F-108 (PF-108)-blended PLGA microfibrous scaffolds that alleviated the hydrophobicity associated with PLGA by enriching the surface of microfibers with the ethylene oxide units present in PF-108.

Methods:

In this study, we report the influence of the extent of surface enrichment of PLGA microfibers on their interaction with two model proteins, ie, bovine serum albumin (BSA) and lysozyme. BSA and lysozyme were adsorbed onto PLGA microfiber meshes (unmodified and modified) and studied for the amount, secondary structure conformation, and bioactivity of released protein.

Results:

Irrespective of the type of protein, PF-108-blended PLGA microfibers showed significantly greater protein adsorption and release than the unblended PLGA samples. However, in comparison with BSA, lysozyme showed a 7–9-fold increase in release. The Fourier transform infrared spectroscopy studies for secondary structure determination demonstrated that irrespective of type of microfiber surface (unblended or blended), adsorbed BSA and lysozyme did not show any significant change in secondary structure (α-helical content) as compared with BSA and/or lysozyme in the free powder state. Further, the bioactivity assay of lysozyme released from blended PLGA microfiber meshes demonstrated 80%–85% bioactivity, indicating that the process of adsorption did not significantly affect biological activity. Therefore, this study demonstrated that the decreased hydrophobicity of blended PLGA microfibrous meshes not only improved the amount of protein adsorbed (lysozyme and BSA) but also maintained the secondary structure and bioactivity of the adsorbed proteins.

Conclusion:

Modulating the hydrophobicity of PLGA via blending with PF-108 could be a viable strategy to improve its interaction with proteins and subsequent cell interaction in tissue engineering applications.

Nanofibers and their applications in tissue engineering

Developing scaffolds that mimic the architecture of tissue at the nanoscale is one of the major challenges in the field of tissue engineering. The development of nanofibers has greatly enhanced the scope for fabricating scaffolds that can potentially meet this challenge. Currently, there are three techniques available for the synthesis of nanofibers: electrospinning, self-assembly, and phase separation. Of these techniques, electrospinning is the most widely studied technique and has also demonstrated the most promising results in terms of tissue engineering applications. The availability of a wide range of natural and synthetic biomaterials has broadened the scope for development of nanofibrous scaffolds, especially using the electrospinning technique. The three dimensional synthetic biodegradable scaffolds designed using nanofibers serve as an excellent framework for cell adhesion, proliferation, and differentiation. Therefore, nanofibers, irrespective of their method of synthesis, have been used as scaffolds for musculoskeletal tissue engineering (including bone, cartilage, ligament, and skeletal muscle), skin tissue engineering, vascular tissue engineering, neural tissue engineering, and as carriers for the controlled delivery of drugs, proteins, and DNA. This review summarizes the currently available techniques for nanofiber synthesis and discusses the use of nanofibers in tissue engineering and drug delivery applications.

Bioresorbable nanofiber-based systems for wound healing and drug delivery: Optimization of fabrication parameters

Wound healing is a complex process that often requires treatment with antibiotics. This article reports the initial development of a biodegradable polymeric nanofiber-based antibiotic delivery system. The functions of such a system would be (a) to serve as a biodegradable gauze, and (b) to serve as an antibiotic delivery system. The polymer used in this study was poly(lactide-co-glycolide) (PLAGA), and nanofibers of PLAGA were fabricated with the use of the electrospinning process. The objective of this study was to determine the effect of fabrication parameters: orifice diameter (needle gauge), polymer solution concentration, and voltage per unit length, on the morphology and diameter of electrospun nanofibers. The needle gauges studied were 16 (1.19 mm), 18 (0.84 mm), and 20 (0.58 mm), and the range of polymer solution concentration studied was from 0.10 g/mL to 0.30 g/mL. The effect of voltage was determined by varying the voltage per unit electrospinning distance, and the range studied was from 0.375 kV/cm to 1.5 kV/cm. In addition, the mass per unit area of the electrospun nanofibers as a function of time was determined and the feasibility of antibiotic (cefazolin) loading into the nanofibers was also studied. The results indicate that the diameter of nanofibers decreased with an increase in needle gauge (decrease in orifice diameter), and increased with an increase in the concentration of the polymer solution. The voltage study demonstrated that the average diameter of the nanofibers decreased with an increase in voltage. However, the effect of voltage on fiber diameter was less pronounced as compared to polymer solution concentration. The results of the areal density study indicated that the mass per unit area of the electrospun nanofibers increased linearly with time. Feasibility of drug incorporation into the nanofibers was demonstrated with the use of cefazolin, a broad-spectrum antibiotic. Overall, these studies demonstrated that PLAGA nanofibers can be tailored to desired diameters through modifications in processing parameters, and that antibiotics such as cefazolin can be incorporated into these nanofibers. Therefore, PLAGA nanofibers show potential as antibiotic delivery systems for the treatment of wounds.

Novel polymer-synthesized ceramic composite-based system for bone repair: Anin vitro evaluation

The emergence of synthetic bone repair scaffolds has been necessitated by the limitations of both autografts and allografts. Several candidate materials are available including degradable polymers and ceramics. However, these materials possess their own limitations that at least in part may be overcome by combining the two materials into a composite. Toward that end, a novel approach to forming a polymer/ceramic composite has been developed that combines degradable poly(lactide-co-glycolide) microspheres and a poorly crystalline calcium phosphate that is synthesized within the microspheres, which are then fused together to form a porous three-dimensional scaffold for bone repair. The design, fabrication, and characterization of the composite microspheres, the calcium phosphate formed within these microspheres, and the formation of scaffolds were studied. The calcium phosphate formed was analyzed by x-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy, and was shown to be similar to native bone in both composition and crystallinity by controlling certain processing parameters such as mixing time, solution pH, and mixing temperature. Scaffolds with porous interconnected structures and mechanical properties in the range of trabecular bone were fabricated via precise control of polymer/ceramic ratios within the microspheres and scaffold heating times. This composite scaffold represents a new and important vehicle for bone-tissue engineering.