polymeric nanoparticles or nanopolymer manufactured through the chemical conjugation of active pharmaceutical ingredients and a water‐soluble polymer have been used to develop a polymer‐drug or polymer‐protein conjugate or pro‐drug compounds which are further used in the treatment of a wide range of diseases. The chemical degradation releases the active pharmaceutical ingredients into the bloodstream or the site of disease (Tong et al. 2009). Likewise, various other nanocarrier systems like liposome, SLN, dendrimers, quantum dots, etc., are promisingly used in the development of efficient drug delivery systems for potential management of diseases (Liang et al. 2014; Núñez et al. 2018; Mitragotri and Stayton 2019). The role of such nano‐based drug delivery systems in the treatment of various diseases has been briefly discussed here.
1.3.2.1 Diabetes
Silica nanoparticles have been used in drug delivery applications for years, as they can be adjusted for continuous or triggered drug release (Bharti et al. 2015). Delivery of insulin across intestinal Caco‐2 cells using silica nanoparticles was reported. Silica nanoparticles, due to high surface area and selective absorption, can be extensively used in drug delivery systems (Bharti et al. 2015). Polymeric nanoparticles have been harnessed for targeted drug delivery and protection of nucleic acids. Interleukin (IL)‐10 and IL‐4 entrapped in polymeric nanoparticles were delivered to white blood cells to reduce the T cell response against native islet cells in prediabetic animal models. It was observed that the polymeric nanoparticles were useful in diabetic treatment as it inhibited the development of diabetes in 75% of the animal models (Singh et al. 2019).
1.3.2.2 Cancer
Porous silica nanoparticles have emerged as an efficient delivery system for cancer therapy. Targeted drug therapy requires zero release before reaching the target site (Bharti et al. 2015). Targeted delivery of Doxorubicin (DOX) using silica nanoparticles coated with PEG have been reported. For the study, 120 mg kg−1 of nanoparticles were injected on a weekly basis for a period of three weeks to a KB‐31 xenograft model. The results of the study showed 85% inhibition of tumor by DOX‐loaded silica nanoparticles in comparison to DOX drug. A study reported curcumin‐containing liposomes conjugated with synthetic RNA aptamer (Apt‐CUR‐NPs) to target epithelial cell adhesion molecule (EpCAM) protein which is observed in colorectal adenocarcinoma. The Apt‐CUR‐NPs depicted enhanced bioactivity of curcumin (CUR) after 24 hours compared to free CUR. Apt‐CUR‐NPs also showed increased binding to HT29 colon cancer cells and cellular uptake. Comparative study of in vitro induced cytotoxicity of free CUR and Apt‐CUR‐NPs in HT29 cell line demonstrated more cytotoxicity of Apt‐CUR‐NPs in comparison to totally free CUR (cellular viabilities about 58% and 72%, respectively) (Rabiee et al. 2018).
1.3.2.3 Psoriasis
Psoriasis is a distinctive chronic inflammatory disease with a strong genetic makeup. Srisuk et al. (2012) evaluated permeability of Methotrexate (MTX)‐entrapped deformable liposomes and devised lipid vesicle from phosphatidylcholine (PC) and oleic acid (OA), and compared with MTX‐entrapped conventional liposomes synthesized using PC and cholesterol (CH) by thin‐film hydration method. MTX entrapped in PC: CH was observed to be more stable in size and loading. Although, MTX‐entrapped PC: OA liposomes increased the skin permeability characterized with higher absorption and flux of MTX diffused across or accumulated in the epidermis and dermis layers of porcine skin (Srisuk et al. 2012; Chandra et al. 2018).
Pinto et al. (2014) also developed and assessed the potential of nanostructured lipid carriers (NLCs) loaded with MTX by hot homogenization technique as a novel technique for topical therapy of psoriasis. The assessment of the in vitro skin permeation of MTX in their study showed its capability to go through the skin barrier when loaded within NLCs formulation which confirms the high potential of NLC as carriers for MTX and feasibility for topical delivery.
1.3.2.4 HIV
To deal with HIV progression and prevent development of resistance, a combination of multiple drugs is given which is known as highly active antiretroviral therapy (HAART). Antiretroviral drugs should be able to cross the mucosal epithelial barrier when used orally. It has been reported that nanoparticles conjugated with antiretroviral drugs have the potential to target monocytes and macrophages in vitro. Poly(lactic‐co‐glycolic acid) (PLGA) nanoparticles were entrapped with three antiretroviral drugs, ritonavir, lopinavir, and efavirenz, and analyzed. It was observed that PLGA nanoparticles depicted sustained drug release for over 4 weeks (28 days), whereas the free drugs within 48 hours (2 days) (Rizvi and Saleh 2018). Thus, nanoparticles could be utilized for drug delivery of anti‐HIV drugs.
1.3.2.5 Neurodegenerative Diseases
Nerve growth factor (NGF) is very crucial for the survival of neurons and can be used a potential therapeutic agent for neurodegenerative disorders. NGF could not cross the blood‐brain barrier (BBB) but can be preferably used as a drug delivery vehicle to transport drugs across BBB. Various studies have reported NGF encapsulated in transferring and cereport‐functionalized liposomes improve the permeability across the BBB. Also, resveratrol in combination with lipid core nanocapsules were found to be highly efficient against Aβ‐induced neurotoxicity. The drug delivery system was observed to improve short‐term and long‐term memory (Singh et al. 2019).
1.3.2.6 Blood Pressure (BP) and Hypertension
Polymer nanoparticles like PLGA, poly(lactic acid) (PLA), and chitosan have been used in conjugation with antihypertensive drugs for targeted and controlled drug delivery. A significant and sustained reduction in blood pressure (BP) has been recorded employing nifedipine conjugated with PLGA, PCl nanoparticles. The most important benefit of sustained release of hypertensive drugs is that it regulates BP fluctuations; also, lower doses are required compared to conventional drugs (Singh et al. 2019). Liposomal drug formulations have also been investigated using animal models for hypertension. It was observed that a single intravenous dose of liposomal formulation encapsulated with vasoactive intestinal peptide normalized BP for longer duration compared to non‐encapsulated peptide. Thus, successful conjugation of anti‐hypertensive drugs with nanoparticles increases drug circulation and also prolongs systemic availability of drugs at required concentrations (Singh et al. 2019).
1.3.2.7 Pulmonary Tuberculosis
Mycobacterium tuberculosis (MTB) is the causative agent for pulmonary tuberculosis causing worldwide deaths. It affects all the parts of the body, but lungs are mostly infected due to inhalation of MTB. Drug dosage for the treatment is generally given orally and repeated doses in high concentration are required for the treatment process. However, drug administration through inhalation is more advantageous and requires lower doses. Encapsulated nanoparticles for drug delivery efficiently penetrate the biological membrane and reach the target site. MSNPs were reported to act as a platform for the delivery of anti‐TB drugs. Functionalized MSNPs could be internalized competently and used as controlled drug delivery vehicles (Singh et al. 2019).
1.4 Advantages and Challenges Associated with Nanomaterials Used in Drug Delivery, Diagnosis, and Treatment of Diseases
Nanotechnology is a double‐edged sword. On one edge, it has revolutionized medicine as well as the healthcare system by introducing innovative ways of developing new drug delivery systems or reformulation of existing drugs, as well as new devices for diagnosis, monitoring, and treatment of diseases owing to their enhanced permeability, retention, and therapeutic effects; the other edge showed potential health risks (Patel et al. 2015). As discussed earlier, nanomaterials which are considered as building blocks of nanotechnology possess novel and unique properties such as small size, high surface
