Stimuli-responsive Electrospun Nanofibers for Controlled Release

It is known that synthetic polymers have been extensively used as scaffolds in the synthesis of nanofibers for drug delivery. During the last years, important researching efforts have been focused on the use of stimuli-responsive systems. This system is automatically responsive to changes in environmental parameters including pH, temperature, light, electrical field, and magnetic field, which can tailor the drug release rate based on the prognostic markers. Most of the recent studies in the area of controlled drug release have been dedicated to the creation of systems for drug encapsulation based on different types of polymer. Creative Biolabs now provides different kinds of stimuli-responsive electrospun nanofibers for our honor clients.

To date, much efforts have been devoted to the development of activation and feedback factors electrospun nanofibers to initiate the release and/or regulate the release rate of drugs over time. Such nanofibers are called smart electrospun nanofibers. This system is automatically responsive to changes in several environmental parameters.

• pH Responsive Electrospun Nanofibers

The pH of human body is regulated by acid-base homeostasis, which keeps the pH of the arterial blood between 7.38 and 7.42. However, many tissues or cell compartments have their own distinctive pH environments for normal functioning. The acidic environment found in tumor tissues can be employed as a way to specifically target the release of antitumor drugs at the tumor in response to the change in pH by the use of nano-formulations sensitive to pH changes. Once nanofibers decorated with targeting module are synthesized by the electrospinning process and loaded with the antitumor drug, treatment may be applied. When the treatment has been inoculated, an internal stimulus such as the low pH present in the tumor tissues, stimulates the release of the drug at the specific site of the tumor, thus applying the treatment on tumor cells.

Fig.1 (a) Schematic of a conventional electrospinning equipment. (b) Schematic illustration of three common methods for preparing stimuli-responsive electrospun nanofibers.¹

Therefore, the pH is one of the most studied stimuli to trigger and modulate the release of drugs. An ideal scenario is that the pH-responsive, drug-loaded electrospun nanofibers release at the characteristic pH of the disease, and when the condition is improved and the pH shifts to the normal value, such nanofibers could reduce the release rate or completely cease the release. Polymers containing amine groups or carboxylic acids are the most widely used pH sensitive polymers. They end up in deprotonation or protonation, associated with changes in morphology and hydrophilicity when placed in different pH environments.

Fig.2 Illustration of the pH-responsive self-assembly and morphological transition of peptide pHly-1 from nanoparticles to nanofibers and the process of treating dental caries by peptide pHly-1.²

• Thermoresponsive Electrospun Nanofibers

Temperature-responsive drug-loaded electrospun nanofibers are made from polymers that undergo abrupt changes in solubility (the affinity of water). This is the result of competition between hydrophilic and hydrophobic moieties on the polymer chain. The balance point is called the lower critical solution temperature (LCST). Among multiple temperature sensitive polymers, poly(N-isopropylacrylamide) (PNIPAAm), poly(N, N-diethylacrylamide) (PDEA), poly(N-vinylcaprolactam) (PVCL), and poly(methyl vinyl ether) (PMVE) have been widely explored as components of thermoresponsive system because their LCSTs are close to normothermia.

• Electric Field Responsive Electrospun Nanofibers

An electric field influences the swelling behavior of electric field responsive polymers. Electric field responsive polymers are mainly classified into the following categories: electroactive polymers, ion-doped conducting polymers, and polymer composites/bends/coatings. Ion transport takes place in conducting polymers during the electro- and/or chemical oxidation and reduction. The reversible intercalation motion of the ions results in a volume change of conducting polymers. The polymeric nanofibers incorporated with carbon nanotubes operating in electrolyte can lead to volume changes because of capacitive charging. Both conducting polymer coated electrospun nanofibers and carbon nanotube encapsulated electrospun nanofibers have been examined for controlled release under electrical stimulation.

• Magnetic Field Responsive Electrospun Nanofibers

Living tissues are magnetically transparent since their compositions are mainly water, which is diamagnetic and negligibly repelled even in a powerful magnetic field. Additionally, the human body is able to tolerate magnetic fields of up to 7 Tesla, while a strong light or heat source usually leads to DNA damage and cell death. In order to generate magnetically responsive fibers, superparamagnetic nanoparticles (SPNs) have been incorporated into polymers during electrospinning.

• Multiple Stimuli Responsive Electrospun Nanofibers

Multi stimuli-responsive electrospun nanofibers that respond to a combination of two or more signals have been developed to extend the broad tunability over the drug delivery. These combined responses can occur at the same time or in a sequential way. For example, dual stimuli-responsive drug-loaded electrospun nanofibers can activate the release of drugs to an infection site whenever the local pH or temperature shifts from the normal value. Multi stimuli-responsive electrospun nanofibers can be a collective body of a few single stimuli-responsive electrospun fibers or can also be made of macromolecules or polymer mixtures/blends or surface coating that respond to multiple stimuli.

Fig.3 Schematic illustration of stimuli-responsive electrospun nanofibers as intelligent drug delivery platform in biomedicine field.¹

Smart electrospun nanofibers offer applications in unique niches such as transdermal drug delivery, oral drug delivery, and vaginal drug delivery etc. Besides, smart nanoparticles and nanofibers can be combined to form a composite/hybrid system for controlled release. Creative Biolabs has devoted much efforts to the development of smart electrospun nanofibers that are responsive to multiple stimuli under normal physiological conditions. If you are interested in our stimuli-responsive electrospun nanofibers for drug targeted delivery and controlled release, please don't hesitate to contact us for more information.

References

1. Chen, Kai, et al. "Stimuli-responsive electrospun nanofibers for drug delivery, cancer therapy, wound dressing, and tissue engineering." Journal of Nanobiotechnology 21.1 (2023): 237.
2. Zhang, Peng, et al. "Dual-sensitive antibacterial peptide nanoparticles prevent dental caries." Theranostics 12.10 (2022): 4818.

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