A novel treatment strategy for preterm birth: Intra-vaginal progesterone-loaded fibrous patches

Abstract

Progesterone-loaded poly(lactic) acid fibrous polymeric patches were produced using electrospinning and pressurized gyration for intra-vaginal application to prevent preterm birth. The patches were intravaginally inserted into rats in the final week of their pregnancy, equivalent to the third trimester of human pregnancy. Maintenance tocolysis with progesterone-loaded patches was elucidated by recording the contractile response of uterine smooth muscle to noradrenaline in pregnant rats. Both progesterone-loaded patches indicated similar results from release and thermal studies, however, patches obtained by electrospinning had smaller average diameters and more uniform dispersion compared to pressurized gyration. Patches obtained by pressurized gyration had better results in production yield and tensile strength than electrospinning; thereby pressurized gyration is better suited for scaled-up production. The patches did not affect cell attachment, viability, and proliferation on Vero cells negatively. Consequently, progesterone-loaded patches are a novel and successful treatment strategy for preventing preterm birth.

Introduction

Preterm birth, also commonly referred to as premature birth, is the birth of a baby who has completed less than 37 weeks of gestation, it is a leading cause of infant mortality under the age of five and it is one of the most crucial research areas in need of new treatment strategies (Kindinger et al., 2017). Around 15 million babies suffer from preterm birth and the number is increasing. Annual health costs associated with surviving babies in the US exceed $ 25 billion per year and climbing (McCormick et al., 2011).

Preterm birth is a syndrome attributed to heterogeneous influences such as a decrease in the action of progesterone (P4), infection, multiple gestations, and cervical disease (Goldenberg et al., 2008). P4, which is a steroid hormone, is a primary prescribed treatment for pre-term births and plays a crucial role in female reproduction with regulatory actions throughout the female reproduction cycle but the mechanism of action is not clear (Graham and Clarke, 1997). P4 may work by activating the anti-inflammatory and pro-relaxation pathways in the uterus, thereby reducing uterine contractility and preventing the onset of premature birth. The rate of preterm birth had declined widely due to P4 treatment in women who are at high risk for preterm birth due to a history of preterm birth or a short cervical length (Nold et al., 2013).

P4 is a poorly water-soluble drug (Cam et al., 2019b) traditionally available in tablet and also gelatinized capsule, vaginal gel, vaginal insert, and injection forms. All forms are daily given except the injection form, which is weekly given. P4 administered orally can cause sleepiness, headaches, back pain, abdominal cramps, constipation, breast tenderness, nausea, dizziness, edema, hypotension, dysphoria, fatigue and may induce a hypercoagulant state. Thus, one of the very significant advantages of P4 given via the vaginal route is its high bioavailability in the uterus as the first pass through the liver is avoided. Although vaginal irritation can be uncomfortable, this route allows for fewer systemic side effects (Goletiani et al., 2007).

Fibrous patches are recognized to be the most prominent micro/nanostructured materials that are presently used in various applications such as bioengineering, healthcare and environmental applications (Cam et al., 2020a). In addition, fibrous patches have very significant advantages such as high permeability, high surface area to volume ratio, low weight, high density of pores and low fiber diameter (Balamurugan et al., 2011). The fibrous patches produced with natural and synthetic polymers have been found to be promising for developing drug delivery systems using several methods. One of the most common and preferred techniques to produce fibrous patches is via electrospinning (Huang et al., 2020, Qin et al., 2019). Moreover, a variety of techniques have been available recently to produce fibrous patches for biomedical applications, one such method is pressurized gyration (Alenezi et al., 2019). Previously, patches for hormone delivery, with some advantages such as controlled release and efficient drug loading, have been produced by electrospinning and pressurized gyration (Brako et al., 2018, Mofidfar and Prausnitz, 2019). In this study, it is aimed to produce a controlled release form of P4 to overcome low bioavailability, side effects, and high frequency of dosage.

Electrospinning is an effective method for making continuous polymeric micro/nanofibrous patches (Fig. 1). Electrospinning is attractive owing primarily to its cost-effectiveness, reproducibility, simplicity and ability to spin a wide range of polymers whilst ensuring the opportunity for direct encapsulation of medicines into the electrospun fibrous patches. Several variable parameters such as polymer solution feed rate, solution composition and applied voltage affect the characteristics of the electrospun fibrous patches (Cam et al., 2019a, Cam et al., 2020b).

An original pressure driven technique for the production of fibrous patches has been established to incorporate concurrent use of pressure, flow, and rotation. The solvent-based production technique, pressurized gyration, simultaneously exploits centrifugal spinning and solution blow spinning to produce fibrous patches (Fig. 1). Pressurized gyration offers an alternative option to electric-field driven technologies such as electrospinning. The advantages of pressurized gyration include the ability to spin charge-absent polymers and a high production yield. Pressurized gyration has a much larger production capacity compared to other generation methods such as electrospinning (Raimi-Abraham et al., 2015). The pressurized gyration system consists of a rotating perforated chamber, which is fed with a polymer solution, containing a series of orifices (24) with dimensions of 0.5 mm on its midline circumference. The rotating speed (12,000–36,000 rpm) of the chamber and the pressurized gas (1 × 10⁵–3 × 10⁵ Pa) affects the characteristics of fibers in terms of final morphology. Essentially, the polymer solution in the chamber is extruded out from the orifices following the rotation of the chamber, and dry fibrous patches are obtained following solvent evaporation of the extruded polymer solution (Heseltine et al., 2018).

In our study, we aim to produce a patch that can be administered vaginally to prevent preterm birth with some possible advantages compared to other treatment strategies, such as reducing side effects, providing a higher bioavailability, and reducing the frequency of dosage. Moreover, the larger production capacity of pressurized gyration for the production of P4-loaded fibrous patches was evaluated and compared to electrospinning. Thus, P4-loaded fibrous patches were produced with two different techniques: Electrospinning and pressurized gyration. These fibrous patches are compared with respect to their ability to increase the dissolution of the poorly soluble drug P4 and also drug incorporation, characterization, release characteristics, tensile strength, short-term cell attachment, long-term viability, and cell proliferation have been tested. In addition, the effect of maintenance tocolysis with P4-loaded fibrous polymeric patches were examined in the uterus of pregnant rats using organ bath experiments, and also compared with the oral route (Fig. 1).