Multifunctional Poly Ethylene Glycol Research Articles

In Situ-forming Collagen Hydrogels Crosslinked by Multifunctional Polyethylene Glycol as a Matrix Therapy for Corneal Defects: 2-Month Follow-up In Vivo.

We recently showed that in situ-forming collagen gels crosslinked through multifunctional polyethylene glycol (PEG) supported corneal epithelialization 7 days after treatment of lamellar keratectomy wounds. In this study, we aimed to evaluate the longer-term regenerative effects of this gel in animals. Corneal wound healing was assessed 60 days after lamellar keratectomy and gel treatment using slitlamp examination, optical coherence tomography (OCT), pachymetry, corneal topography, an ocular response analyzer, and tonometry. The corneas were evaluated for the presence of beta-tubulin, cytokeratin 3, zonula occludens-1, and alpha smooth muscle actin (SMA) markers. Gene expression of aldehyde dehydrogenase 3A1 (ALDH3A1), cluster of differentiation 31, CD163, alpha-SMA, hepatocyte growth factor, and fibroblast growth factor 2 (FGF-2) and protein expression of CD44 and collagen VI were evaluated. Intraocular pressure, corneal thickness, and hysteresis for the corneas treated with collagen-PEG gels did not significantly change compared with the saline group. However, placido disk topography revealed greater regularity of the central cornea in the gel-treated group compared to the saline group. The gel-treated group exhibited a lower degree of epithelial hyperplasia than the saline group. Immunohistochemical and gene expression analysis showed that the gel-treated corneas exhibited lower alpha-SMA expression compared with the saline group. CD163 and CD44 were found to be elevated in the saline-treated group compared with normal corneas. The in situ-forming collagen-PEG gel promoted epithelialization that improved central corneal topography, epithelial layer morphology, and reduced expression of fibrotic and inflammatory biomarkers after 60 days compared to the saline group.

In vivo biocompatibility evaluation of in situ-forming polyethylene glycol-collagen hydrogels in corneal defects

The available treatment options include corneal transplantation for significant corneal defects and opacity. However, shortage of donor corneas and safety issues in performing corneal transplantation are the main limitations. Accordingly, we adopted the injectable in situ-forming hydrogels of collagen type I crosslinked via multifunctional polyethylene glycol (PEG)-N-hydroxysuccinimide (NHS) for treatment and evaluated in vivo biocompatibility. The New Zealand White rabbits (N = 20) were randomly grouped into the keratectomy-only and keratectomy with PEG-collagen hydrogel-treated groups. Samples were processed for immunohistochemical evaluation. In both clinical and histologic observations, epithelial cells were able to migrate and form multilayers over the PEG-collagen hydrogels at the site of the corneal stromal defect. There was no evidence of inflammatory or immunological reactions or increased IOP for PEG-collagen hydrogel-treated corneas during the four weeks of observation. Immunohistochemistry revealed the presence of α-smooth muscle actin (α-SMA) in the superior corneal stroma of the keratectomy-only group (indicative of fibrotic healing), whereas low stromal α-SMA expression was detected in the keratectomy with PEG-collagen hydrogel-treated group. Taken together, we suggest that PEG-collagen may be used as a safe and effective alternative in treating corneal defect in clinical setting.

In situ-forming collagen hydrogel crosslinked via multi-functional PEG as a matrix therapy for corneal defects

Visually significant corneal injuries and subsequent scarring collectively represent a major global human health challenge, affecting millions of people worldwide. Unfortunately, less than 2% of patients who could benefit from a sight-restoring corneal transplant have access to cadaveric donor corneal tissue. Thus, there is a critical need for new ways to repair corneal defects that drive proper epithelialization and stromal remodeling of the wounded area without the need for cadeveric donor corneas. Emerging therapies to replace the need for donor corneas include pre-formed biosynthetic buttons and in situ-forming matrices that strive to achieve the transparency, biocompatibility, patient comfort, and biointegration that is possible with native tissue. Herein, we report on the development of an in situ-forming hydrogel of collagen type I crosslinked via multi-functional polyethylene glycol (PEG)-N-hydroxysuccinimide (NHS) and characterize its biophysical properties and regenerative capacity both in vitro and in vivo. The hydrogels form under ambient conditions within minutes upon mixing without the need for an external catalyst or trigger such as light or heat, and their transparency, degradability, and stiffness are modulated as a function of number of PEG arms and concentration of PEG. In addition, in situ-forming PEG-collagen hydrogels support the migration and proliferation of corneal epithelial and stromal cells on their surface. In vivo studies in which the hydrogels were formed in situ over stromal keratectomy wounds without sutures showed that they supported multi-layered surface epithelialization. Overall, the in situ forming PEG-collagen hydrogels exhibited physical and biological properties desirable for a corneal stromal defect wound repair matrix that could be applied without the need for sutures or an external trigger such as a catalyst or light energy.

Short peptide analogs as alternatives to collagen in pro-regenerative corneal implants

Short collagen-like peptides (CLPs) are being proposed as alternatives to full-length collagen for use in tissue engineering, on their own as soft hydrogels, or conjugated to synthetic polymer for mechanical strength. However, despite intended clinical use, little is known about their safety and efficacy, mechanism of action or degree of similarity to the full-length counterparts they mimic. Here, we show the functional equivalence of a CLP conjugated to polyethylene glycol (CLP-PEG) to full-length recombinant human collagen in vitro and in promoting stable regeneration of corneal tissue and nerves in a pre-clinical mini-pig model. We also show that these peptide analogs exerted their pro-regeneration effects through stimulating extracellular vesicle production by host cells. Our results support future use of CLP-PEG implants for corneal regeneration, suggesting the feasibility of these or similar peptide analogs in clinical application in the eye and other tissues. Statement of significanceAlthough biomaterials comprising full-length recombinant human collagen and extracted animal collagen have been evaluated and used clinically, these macromolecules provide only a limited number of functional groups amenable to chemical modification or crosslinking and are demanding to process. Synthetic, customizable analogs that are functionally equivalent, and can be readily scaled-up are therefore very desirable for pre-clinical to clinical translation. Here, we demonstrate, using cornea regeneration as our test bed, that collagen-like-peptides conjugated to multifunctional polyethylene glycol (CLP-PEG) when grafted into mini-pigs as corneal implants were functionally equivalent to recombinant human collagen-based implants that were successfully tested in patients. We also show for the first time that these materials affected regeneration through stimulation of extracellular vesicle production by endogenous host cells that have migrated into the CLP-PEG scaffolds.

Multifunctional PEG modified DOX loaded mesoporous silica nanoparticle@CuS nanohybrids as photo-thermal agent and thermal-triggered drug release vehicle for hepatocellular carcinoma treatment

The combination of a multi-therapeutic mode with a controlled fashion is a key improvement in nanomedicine. Here, we synthesized polyethylene glycol (PEG)-modified doxorubicin (DOX)-loaded mesoporous silica nanoparticle (MSN) @CuS nanohybrids as efficient drug delivery carriers, combined with photothermal therapy and chemotherapy to enhance the therapeutic efficacy on hepatocellular carcinoma (HCC). The physical properties of the nanohybrids were characterized by transmission electron microscopy (TEM), N2 adsorption and desorption experiments and by the Vis-NIR absorption spectra. The results showed that the doxorubicin could be stored in the inner pores of mesoporous silica nanoparticles; the CuS nanoparticles, which are coated on the surface of a mesoporous silica nanoparticle, could serve as efficient photothermal therapy (PTT) agents; the loaded drug release could be easily triggered by NIR irradiation. The combination of the PTT treatment with controlled chemotherapy could further enhance the cancer ablation ability compared to any of the single approaches alone. Hence, the reported PEG-modified DOX-loaded mesoporous silica nanoparticle@CuS nanohybrids might be very promising therapeutic agents for HCC treatment.

Multifunctional PEG retinylamine conjugate provides prolonged protection against retinal degeneration in mice.

A polyethylene glycol (PEG) retinylamine (Ret-NH2) conjugate PEG-GFL-NH-Ret with a glycine-phenylalanine-leucine (GFL) spacer was synthesized for controlled oral delivery of Ret-NH2 to treat retinal degenerative diseases, including Stargardt disease (STGD) and age-related macular degeneration (AMD). The peptide spacer was introduced for sustained release of the drug by digestive enzymes in the gastrointestinal tract. The pharmacokinetics experiments showed that the PEG conjugate could control the sustained drug release after oral administration and had much lower nonspecific liver drug accumulation than the free drug in wild-type female C57BL mice. In the mean time, the conjugate maintained the same concentration of Ret-NH2 in the eye as the free drug. Also, PEG-GFL-NH-Ret at a Ret-NH2 equivalent dose of 25 mg/kg produced complete protection of Abca4–/–Rdh8–/– mouse retinas against light-induced retinal degeneration for 3 days after oral administration, as revealed by OCT retina imaging, whereas free Ret-NH2 did not provide any protection under identical conditions. The polymer conjugate PEG-GFL-NH-Ret has great potential for controlled delivery of Ret-NH2 to the eye for effective protection against retinal degenerative diseases.

Amine Functionalization of Collagen Matrices with Multifunctional Polyethylene Glycol Systems

A method to functionalize collagen-based biomaterials with free amine groups was established in an attempt to improve their potential for tethering of bioactive molecules. Collagen sponges were incorporated with amine-terminated multifunctional polyethylene glycol (PEG) derivatives after N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide and N-hydroxysuccinimide (EDC/NHS) cross-linking. The extent of the incorporation of different amounts and different numbers of active moieties of amine-terminated PEG systems into the collagen scaffolds was evaluated using ninhydrin assay, Fourier transform infrared spectrophotometry (FTIR), collagenase degradation assay, denaturation temperature measurements, and in vitro cell studies. A 3% 8-arm amine-terminated PEG was found to be the minimum required effective concentration to functionalize EDC/NHS stabilized collagen scaffolds. EDC/NHS stabilized scaffolds treated with 3% 8-arm amine-terminated PEG exhibited significantly improved denaturation temperature and resistance to collagenase degradation over non-cross-linked scaffolds (p < 0.002). Biological evaluation using 3T3 cells demonstrated that the produced scaffolds facilitated maintenance of the cells' morphology, metabolic activity, and ability to proliferate in vitro. Overall, our results indicate that amine-terminated PEG systems can be used as means to enhance the functionality of collagenous structures.

Syntheses of Click PEG−Dexamethasone Conjugates for the Treatment of Rheumatoid Arthritis

A novel linear multifunctional polyethylene glycol (PEG)-dexamethasone (Dex) conjugate (click PEG-Dex) was synthesized using facile Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (a click reaction). Dex was conjugated to the click PEG via an acid-labile hydrazone bond to allow the drug release in a pathophysiological environment. To evaluate click PEG's potential as a versatile drug delivery platform, the click PEG-Dex conjugates were tested in an adjuvant-induced arthritis (AA) rat model. In vivo optical imaging data confirmed the arthrotropism of the conjugates in the arthritic rats. A long-term treatment study revealed that a single click PEG-Dex conjugate administration provided sustained (>15 days) amelioration of ankle joint inflammation to the AA rats. Treatment with an equivalent dose of dexamethasone phosphate sodium (free Dex) only provided temporal resolution of the arthritis, which recurred upon treatment withdrawal. Further histological and bone mineral density comparison between the ankle joints from both click PEG-Dex and free Dex treatment groups confirmed the superior anti-inflammatory and disease modifying effects of the novel polymer-drug conjugates.

MultiPEGs: High Molecular Weight Multifunctional Poly(ethylene glycol)s Assembled by a Dendrimer‐Like Approach

AbstractNew multifunctional, soluble and biocompatible polymeric systems exhibiting good physicochemical properties and good binding capacity have been obtained by assembly of smaller PEG components, selectively protected, purified and activated, by use of appropriate polyfunctional linkers. A general process for the synthesis of those derivatives was characterized by: a) selective derivatization of a PEG unit with a defined MW with an appropriate protecting group and activation of residual functional groups, and b) multiple condensation reactions of PEG units and linkers to provide multifunctional polyethylene glycol derivatives (MultiPEGs) of the desired size and complex structure. These complex‐structured MultiPEGs have larger numbers of functional groups, and probably better biodegradability, than commercial PEGs of comparable molecular weight. They can be advantageously used as carriers or stabilizers of pharmacologically or biologically active substances, and also as soluble supports for reagents and catalysts in liquid‐phase synthesis reactions. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)

A tissue sealant based on reactive multifunctional polyethylene glycol

A tissue sealant based on reactive multifunctional polyethylene glycol