Nanotechnology is the new science dealing with nanometer (nm) size, and nanoparticles (NPs) are one of the nanotechnology building blocks [1,2,3]. Nanotechnology combined with polymers has recently captivated immense interest in many fields including the pharmaceutical industry and medical field. NPs are the nanometer-ranging stable colloidal particles, i.e., from 10 to 1000 nm [4]. They show unusual physical and chemical properties, owing to their smaller size and larger surface area. Nanoparticles can be made from naturally occurring polymers like protein, polysaccharide or synthetic polymer like polystyrene. Nanoparticles made from natural polymers, by comparison, give both mild and easy preparation procedures without using organic solvent and higher shear force. Due to their intrinsic biological properties, chitosan nanoparticles have gained significant interest in the current scenario over the past years.
Chitosan nanoparticles (CNPs) are used in a range of various products and applications, ranging from medicinal, drug delivery, tissue engineering, and food processing to bio-sensing, immobilization of enzymes, fuel cell development, and wastewater treatment [5]. Chitosan [poly(b-1/4)-2-amino-2-deoxy-D-glucopyranose] is a biopolymer which is a chitin derivative, extracted from the shellfish exoskeleton [6,7,8]. Chitosan has properties forming a film, fiber, and micro/nanoparticle, for its abundance, low cost of manufacturing, biodegradability, biocompatibility, reusable, and non-toxic nature. Because of their capacity to provide safety and stability, chitosan nanoparticles were used in the delivery of active components. Recently, extensive research has been carried out on chitosan nanoparticles to target biomolecules including anticancer chemotherapy [9], antibiotics [10], vaccines [11], peptides, genes [12], etc.
Polymers like chitosan nanoparticles are ideal shielding agents and can be used to deliver active ingredients. To date, CNPs ranging from few to several hundred nanometers have been manufactured using chemosynthetic techniques such as microemulsion, oil-water emulsion, spray-drying, precipitation, complex formation of polyelectrolytes, and methods of desolvation [13]. Nevertheless, due to the high solution viscosity and coiled nature of high molecular weight chitosan (HMWC), these synthetic techniques result in the creation of microparticles of more than 1000 nm. The entry of drug-charged particles into cells with pore sizes below 1000 nm in vivo is severely limited. It was calculated that the efficiency of cellular absorption of polymeric particles with a diameter of less than 1000 nm was 2.5–250 times greater than particles exceeding the nanometer scale [14]. Chemosynthetic techniques often rely on stabilizing agents such as polyethylene glycol (PEG), polyvinyl alcohol, and succinate D-alpha-tocopheryl poly (ethylene glycol) [15]. Such additional surface stabilizers significantly improve the half-life of nanoparticles by enhancing the longevity of NPs in the blood, which can induce nanotoxicity [16].
Eventually, regulating the size and shape of nanoparticles by enhancing current physicochemical techniques was seen as a priority for material scientists to reduce, size-oriented limitations of polymeric nanoparticles. In this context, green nanotechnology, a well-established interdisciplinary nanoscience branch, has shown huge potential for creating nanostructures that are strictly within the range of a few nanometers, using biological systems like plants, fungi, and bacteria [17, 18]. Cross-linking chitosan (CS) with sodium tripolyphosphate (TPP) is a moderate, efficient approach for achieving CNPs. The nanoparticles are formed by the ionic gelation method, where electrostatic interaction between positively charged CS and negatively charged TPP molecules are cross-linked to form a chitosan nanoparticle.
Chitosan nanoparticles were loaded with various plants such as Arrabidaea chica [19], Mentha longifolia [20], Leucas aspera [21], and others. The physicochemical properties of chitosan nanoparticles such as size, surface area, cationic composition, effective functional groups, high permeability towards biological membranes, non-toxicity to individuals, cost efficiency, higher encapsulation performance and/or by mixing with other compounds and wide-ranging antifungal and antimicrobial activities have resulted in increased use in biomedical applications [22,23,24,25]. Thus, due to the extensive applications, chitosan polymer was chosen for the present research.
Pterocarpus marsupium plant belongs to the Fabaceae family and because of its diverse biological activities since ancient times it has been used in India and its neighboring countries. All parts of the plant are used as primitive home remedies against various human diseases. This was commonly used in homeopathic medicine, Unani systems, and ayurvedic [26, 27]. It is also commonly referred to as Malabar kino or Indian kino tree or Vijayasar, it is a medium to large deciduous tree which can grow up to 30 m (98 ft.) tall [28, 29]. This is native to India, Nepal, and Srilanka. Heartwood (stem bark) is golden-yellow in color, possessing antidiabetic, astringent, anti-inflammatory, hypertriglyceridemic, cardiotonic, wound healing, hepatoprotective function, and as a potent COX-2 inhibitor [30,31,32,33]. The plant P. marsupium was recognized as a very rich source of flavonoids and polyphenolic substances by earlier researchers [34]. All of P. marsupium functional phytoconstituents were thermostable. An active compound, epicatechin, was detected from the PM bark ethanol extract and the presence of three phenolic compounds pterostilbene, pterosupin, and marsupin as antidiabetic agents in ethylacetate-soluble portions of aqueous extract of PM heartwood was reported [35]. Traditionally different plants have been used as anti-inflammatory agents. In Indian medicine P. marsupium was used from ancient times to treat burns, psoriasis, wounds, odontalgia, etc. [36]. The most significant biologically active ingredients in stem bark were terpenoids, saponins, tannins, alkaloids, flavonoids, and phenolic compounds. Due to various pharmacological activities, the plant Pterocarpus marsupium was taken in the present research.
The current research has been conducted to formulate and establish strategies to increase the therapeutic potential of standardized Pterocarpus marsupium heartwood extract using CNPs as carriers. The parameters have been modified to produce the optimal output of NPs. Introducing nanotechnology to plant extracts has provided a beneficial strategy for herbal medicinal products, taking into account the several features to be offered by nanostructured systems includes increasing solubility, pharmacological activity, bioavailability, safety from toxicity, controlled delivery, and safety from physical and chemical degradation [37, 38]. At present, processes in nanotechnology involving medicinal plants have produced several novel delivery methods, including polymeric nanoparticles. Those made from biocompatible and biodegradable polymers such as chitosan (CS) provide an alternative for sustained drug delivery [39]. These prepared green synthesized chitosan nanoparticles were characterized for size and morphology, drug entrapment efficiency, and drug release studies. These are evaluated for their anti-diabetic and anti-inflammatory activities.