Chitosan/PLGA shell nanoparticles as Tylotoin delivery ...

Introduction

Skin damage is inevitable, and wounds caused by adverse factors, such as surgery and accidents, are common in everyday life, affect health, and even endanger lives [1]. However, wound healing is a complex and highly coordinated process, and the disturbance of any phase may result in incomplete and inadequate recovery of the wound tissue [2], [3]. Current drugs for wound healing have many disadvantages, such as low activity, frequent replacement, and tendency to scarring [4], [5]. Wound scabs are formed when platelets and fibrous proteins coagulate at the injury site and usually appear 2–3 days after the injury [6]. Most wound dressings cannot be used to covered crusts wound [7]. As a result, safe and effective treatments are needed to improve skin wound healing.

Naturally derived, multifunctional, highly active bioactive peptides with antibacterial, pro-migration, anti-inflammatory, and scar-free properties are attracting a lot of attention [8]. Tylotoin, a peptide molecule from the skin of a salamander (Tylototriton verrucosus), has the ability to promote wound healing [9]. Previous studies found that Tylotoin promotes the migration and proliferation of keratinocytes, fibroblasts, and vascular endothelial cells; release of TGF-1 and IL-6; macrophage recruitment; and fibroblast to myofibroblast differentiation. With only 12 amino acid residues and a small molecular weight, Tylotoin can be a novel wound healing drug candidate [10]. However, the wide use of Tylotoin is limited by the characteristics of natural peptides, such as easy degradation and difficulty in transdermal delivery [11]. Hence, delivery carriers should be urgently developed to improve stability, enhance drug bioavailability through long-term sustained release, and overcome the skin barrier function.

Poly (lactic-co-glycolic acid) (PLGA) is a biodegradable polymer with high biosafety, good biocompatibility, and sustained-release properties and is widely used as drug carrier and tissue engineering stent materials for clinical treatment [12], [13]. Previous studies used PLGA nanosheets loaded with human recombinant basic fibroblast growth factor (bFGF) to investigate the release of bFGF and the healing behavior of skin defects on the back of mice [14]. PLGA can be hydrolyzed in vivo to produce lactic acid, and this phenomenon can promote angiogenesis in wound healing [15], [16].

Chitosan (CS) is a semi-processed natural basic polysaccharide with a cationic nature capable of forming complexes with anions [17], [18]. CS is used in a variety of biomedical applications due to its good biocompatibility, biodegradability and safety [19], [20]. In addition, CS has good antibacterial, anti-inflammatory, biological adhesion, and hemostatic properties [21], [22], which can enhance the penetration of macromolecules on mucosal surfaces [23], and can be used as a dressing for the treatment of open wounds. A CS nanoparticle is successfully prepared by ionic gelation and rapidly promotes wound healing by accelerating hemostatic activity [24]. CS provides protection, improves stability, facilitates drug absorption and has significant sustained release of the drug after drug loading [25]. In addition, carboxymethyl CS has been used as a CS derivative to deliver active peptides for wound treatment applications. Previously, we found that the carboxymethyl CS-encapsulated delivery of the antimicrobial peptide OH-30 is effective in promoting scar-free wound healing [26].

In this study, we have prepared CS-PLGA-Tylotoin nanoparticles (CPT NPs) by the double-emulsion (W/O/W) method (Scheme 1A). We believe that CPT NPs have hemostatic, antibacterial, fibroblast migration, and proliferative properties (Scheme 1B). CPT NPs sustained release of Tylotoin is through the disintegration in layers after the topical administration of a single dose. In particular, CPT NPs continue to be released even after the wound has been covered with a scab, thereby achieving reduction in the frequency of administration, overcoming the skin barrier function and increasing drug bioavailability.

Section snippets

Materials

CS (Average MW of 224,000, Degree of Deacetylation ≥95 %) and PLGA (50/50, w/w; MW 15,000) were procured from Aladdin (Shanghai, China) and Jinan Daigang Biomaterial Co., Ltd. (Jinan, China), respectively. Polyvinyl alcohol (PVA, MW 13,000-23,000) was purchased from Acros Organics (Shanghai, China). Tylotoin (KCVRQNNKRVCK) was synthesized by GL Biochem Ltd. (Shanghai, China), and high-performance liquid chromatography (HPLC) and mass spectrometry showed that its purity is 98 %.

Preparation of CPT NPs

NPs were prepared

Preparation and optimization of CPT NPs

Particle size, zeta potential, EE%, and DL% are important physicochemical parameters for the evaluation of NPs. Particle size results showed that as the amount of Tylotoin increased from 0.1 mg to 1.0 mg, the particle size of the prepared CPT NPs increased from 293.47 ± 10.28 nm to 320.87 ± 5.45 nm, whereas the zeta potential increased from 18.50 ± 0.69 mV to 22.63 ± 0.75 mV (Table 1). Results showed that the prepared CPT NPs had uniform particle size (293–320 nm). The particle size of the

Conclusion

In this study, CS and PLGA loaded Tylotoin were used to construct a drug delivery system for CPT NPs with wound healing promoting properties. CPT NPs showed improved drug stability, reduced initial release, cascaded disintegration, and 64.61 % Tylotoin sustained release within 14 days. After modification of PT NPs by CS, CPT NPs exhibited good antibacterial activity, hemostatic properties and biocompatibility. During the wound healing process, the outermost layer of CS stopped the bleeding and

CRediT authorship contribution statement

Yirong Wang: Visualization, Data curation, Writing - original draft, Project administration. Li Guo: Data curation, Software. Jiao Liu: Visualization, Investigation. Xiaofei Huang: Formal analysis. Xinxin Wang: Writing - Reviewing, Editing. Xiaolong Guo: Validation, Supervision. Xinguo You: Investigation, Validation. Wenhui Li: Supervision, Investigation. Lili Li:Validation.Tongyi Sun: Conceptualization, Writing -.

review & editing, Funding acquisition. Yuanyuan Gao: Conceptualization, Writing -

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work is supported by the Youth Innovative Team Development Plan of Universities in Shandong Province (2019KJM003). Prof Y. Gao thanks to the Colleges and Universities Youth Innovation Team Talent Induction Program of Shandong Province "Precision Drug Delivery and Diagnosis and Treatment Application Innovation Team".