Photo-cross-linked biodegradable thermo- and pH-responsive hydrogels for controlled drug release

Enhancement of Antibacterial and Mechanical Properties of Photocurable ε-Poly-l-lysine Hydrogels by Tannic Acid Treatment

In this study, a photocurable hydrogel based on an ε-poly-l-lysine (EPL) composite was fabricated by a grafting reaction using glycidyl methacrylate and then complexed with tannic acid (TA) to improve the mechanical stability and antibacterial performance of the EPL hydrogels. UV-visible spectrophotometry, nuclear magnetic resonance, and Fourier transform infrared spectroscopy were introduced to characterize the chemical construction. The obtained EPLMA hydrogel was immersed into TA solution to induce the forming of the H-bond between EPL and TA, resulting in double networks in the composite hydrogel (EPLMA-TA). Due to the additional hydrogen-bond interaction between TA and EPLMA, the mechanical properties of hydrogels were improved and supported cell growth and proliferation. In addition, the antibacterial properties and antioxidant activities of the EPLMA-TA hydrogels were greatly enhanced due to the addition of TA. All the findings indicate that the EPLMA-TA hydrogels with multiple properties show great potential for biomedicine applications.

pH-Responsive Polypeptide-Based Smart Nano-Carriers for Theranostic Applications

Smart nano-carriers have attained great significance in the biomedical field due to their versatile and interesting designs with different functionalities. The initial stages of the development of nanocarriers mainly focused on the guest loading efficiency, biocompatibility of the host and the circulation time. Later the requirements of less side effects with more efficacy arose by attributing targetability and stimuli-responsive characteristics to nano-carriers along with their bio- compatibility. Researchers are utilizing many stimuli-responsive polymers for the better release of the guest molecules at the targeted sites. Among these, pH-triggered release achieves increasing importance because of the pH variation in different organ and cancer cells of acidic pH. This specific feature is utilized to release the guest molecules more precisely in the targeted site by designing polymers having specific functionality with the pH dependent morphology change characteristics. In this review, we mainly concert on the pH-responsive polypeptides and some interesting nano-carrier designs for the effective theranostic applications. Also, emphasis is made on pharmaceutical application of the different nano-carriers with respect to the organ, tissue and cellular level pH environment.

Multifunctional smart hydrogels: potential in tissue engineering and cancer therapy

In recent years, clinical applications have been proposed for various hydrogel products. Hydrogels can be derived from animal tissues, plant extracts and/or adipose tissue extracellular matrices; each type of hydrogel presents significantly different functional properties and may be used for many different applications, including medical therapies, environmental pollution treatments, and industrial materials. Due to complicated preparation techniques and the complexities associated with the selection of suitable materials, the applications of many host-guest supramolecular polymeric hydrogels are limited. Thus, improvements in the design and construction of smart materials are highly desirable in order to increase the lifetimes of functional materials. Here, we summarize different functional hydrogels and their varied preparation methods and source materials. The multifunctional properties of hydrogels, particularly their unique ability to adapt to certain environmental stimuli, are chiefly based on the incorporation of smart materials. Smart materials may be temperature sensitive, pH sensitive, pH/temperature dual sensitive, photoresponsive or salt responsive and may be used for hydrogel wound repair, hydrogel bone repair, hydrogel drug delivery, cancer therapy, and so on. This review focuses on the recent development of smart hydrogels for tissue engineering applications and describes some of the latest advances in using smart materials to create hydrogels for cancer therapy.

Photo-cross-linked biodegradable hydrogels based on n-arm-poly(ethylene glycol), poly(ε-caprolactone) and/or methacrylic acid for controlled drug release

In this paper, a novel kind of photo-cross-linked biodegradable hydrogels based on n-arm-poly(ethylene glycol) ( n = 2, 3, and 4) and poly(ɛ-caprolactone) was prepared by ultraviolet-initiated free radical polymerization. The resulting n-arm-poly(ethylene glycol)-poly(ɛ-caprolactone) and n-arm-poly(ethylene glycol)-poly(ɛ-caprolactone) acrylate (n-arm-PEG-PCL-AC, macromer) were characterized by proton nuclear magnetic resonance and fourier transform infrared spectra. The influences of arm numbers and concentration of macromer on the properties of hydrogel were researched systematically, and the results showed that the gelation time, equilibrium swelling ratio, in vitro degradation, and drug release rate decreased with the increase of arm numbers and concentration of macromer. The degradation and drug release rate could be controlled by varying the cross-linking density of hydrogel, indicating a potential application as controlled drug delivery system. Cytotoxicity test of hydrogel extracts was conducted using L929 mouse fibroblasts, and the relative growth rate exceeded 75% (cytotoxicity type: class 1) after incubation for 24 h, showing excellent cytocompatibility. In addition, the paper presented a pH-sensitive hydrogel (G4_pH) based on 4-arm-PEG-PCL-AC and acrylic acid, and the influences of pH value on swelling behaviors and in vitro drug release of the pH-sensitive hydrogel were examined. The hydrogels shrank under acidic condition and would swell in neutral or basic medium. The pH-dependent drug release behaviors indicated a promising application of the materials as oral drug delivery vehicles.

Fibrillar gels via the self-assembly of poly(l-glutamate)-based statistical copolymers

The synthesis of smart polypeptide hydrogels from photo-crosslinked self-assembled poly(γ-benzyl-l-glutamate-co-allylglycine) organogels is described.