INTRODUCTION:

Typically, microparticles are free-flowing powders with sizes between 1 and 1000 μm, composed of both natural and manmade polymers. The microparticulate carrier system called microspheres is being exploited as a revolutionary medicine delivery method these days. The microspheres carry the therapeutic material to the intended site at a rate and concentration that maximizes therapeutic efficacy and minimizes side effects. That being said, there are a few shortcomings. Microspheres are relatively fragile and difficult to make since they denature in a few of weeks¹.

Multiparticulate carriers are employed in the delivery of drugs to specified sites. These days, solid microspheres are employed in many different ways². Numerous contemporary pharmaceuticals suffer from issues like poor stability, high potency, and low solubility; the way these drugs are delivered affects their effectiveness, commercialization potential, and nature.

Consequently, numerous drug delivery methods have been developed to ensure that the therapeutic agent reaches the right part of the body at the right time and in the right quantity, optimizing effectiveness and reducing side effects while simultaneously boosting adherence.

Types of Drug Delivery System are:

1. Liposome

2. Niosome

3. Nanoparticles

4. Microparticles

Figure 1: Microparticles³

Microparticles:

The term "microparticles" refers to polymeric entities with a size between one and one thousand micrometers. They come in two different forms:

Figure 2: Types of Microparticle⁴

1. Microcapsules:

"Microencapsulation is the process of enclosing a material inside a tiny capsule. Microcapsules are tiny spheres with a uniform wall surrounding them. The microcapsule's shell/coating is referred to as the shell/coating, and its core/internal phase as the core/internal phase. The size of microcapsules varies from 1 to 7 mm. Encapsulating solids, liquids, or gases can alter the shape and size of the resulting capsules⁵.

Types of Microcapsules:

1. Mononuclear/Single core.

2. Poly nuclear/Multiple core.

3. Matrix type.

Figure 3: Types of Microcapsules

2. Microspheres:

Microspheres consist of spherical particles with a diameter less than 200 and are in the form of free-flowing powder. It can be injected with a needle with a number of 18 or 20. They are composed of artificial polymers derived from nature or biodegradable proteins. The therapeutic efficacy of a medication can be increased while simultaneously addressing some of the shortcomings of conventional therapy with a well-designed controlled drug delivery system.

Types of Microsphere:

1. Bioadhesive Microsphere

2. Floating Microsphere

3. Radioactive Microsphere

4. Magnetic Microsphere

5. Polymer Microspheres

a. Advantages of Microparticles:

1. "It guards against enzymatic degradation of the medication enclosed."

2. It is easy to put into practice.

3. This technique helps to mask off bad flavors.

4. They help to increase the relative bioavailability of medications.

5. This method makes it possible to precisely administer medication at designated sites.

6. Tiny particles reduce the toxicity of drugs.

7. Microparticles, or desirable physical properties, are also used in the production of amorphous drugs.

8. Local adverse effects of drugs on oral intake, like gastrointestinal pain, are also lessened.

9. By using this method, a sustained-release formulation with a lower drug dose is created, which improves patient compliance and helps to maintain plasma concentration.

10. Gene therapy, vaccinations, and transfection all use pH-activated microparticles.

11. High concentrations of water-soluble medications can be administered via parenteral microparticles without having a significant osmotic effect at the injection site.

12. They can also be kept for a longer amount of time in suspension or as dry particles.

13. For those who are unable to chew, these microparticles are available as tablets with an effervescent disintegration agent⁶.

b. Disadvantages of Microparticles:

Despite their impressive size, the tiny particles have a few disadvantages, which include the following:

1. "Compared to regular formulations, controlled release formulations have higher material and processing costs.

2. The fate of the polymer matrix and its influence on the environment

3. Polymer additives include plasticizers, stabilisers, antioxidants, and fillers.

4. Reproducibility is lacking.

5. The stability of the drug can be impacted by variations in temperature, pH, and the addition of solvents.

6. Aggregation of particles occurs as a result of their tiny size and huge surface area, making physical handling of micro particles in liquid and dry forms problematic.

7. These issues must be resolved before micro particles can be employed in clinical settings⁷.

Method of preparations⁸:

There are various techniques for the preparation of micro particles. Some of them are listed below:

1. Emulsions-solvent evaporation (o/w, w/o, o/o)

2. Phase separation technique (non solvent addition and solvent partitioning)

3. Interfacial polymerization

4. Spray drying

5. Hot melt microencapsulation

6. Solvent/Emulsion extraction process

7. Fluidized bed coating

Evaluation of microparticles:^9,10

1. Particle Size and shape: Scanning electron microscopy (SEM) and conventional light microscopy (LM) are the methods most frequently used to view micro particles.

2. Electron spectroscopy for chemical analysis: Electron spectroscopy for chemical analysis (ESCA) can be used to determine the surface chemistry of the microspheres.

3. Density determination: A multi-volume pycnometer can be used to determine the microparticles' density.

4. Isoelectric point: The isoelectric point can be ascertained by measuring the electrophoretic mobility of microspheres using micro electrophoresis.

5. The angle of contact: To angle of contact is measured to determine the wetting property of a micro particulate carrier.

6. In vitro methods: Release tests are conducted using various appropriate dissolving media for various kinds of microparticles.

7. Drug entrapment efficiency: Drug entrapment efficiency can be calculated using the following equation, % Entrapment = Actual content/Theoretical content x 100.

8. Swelling index: The swelling index of the microsphere was calculated by using the formula, Swelling index= (mass of swollen microspheres – a mass of dry microspheres/mass of dried microspheres) 100.

Application:

1. A variety of products in the pharmaceutical and biotechnology industries, cosmetics, diagnostic tools, biological filtration devices, veterinary and zoological technologies, foods and food additives, flavors, fragrances, paints, detergents, industrial chemicals, packaging, textiles, and materials for the arts and photography are among the items for which microcapsules are used.

2. These microcapsules can be used to provide a consistent and regulated release, lessen the vaporization of volatile oils, shield medications that are susceptible to oxidation, light, or moisture, cover offensive tastes and odors, turn liquids into powders, and separate incompatible materials within a single system.

3. Amoxicillin, ampicillin, bacampicillin, cephalexin, cephradine, chloramphenicol, clarithromycin, erythromycin, potassium pheneticillin, ofloxacin, and ciprofloxacin are examples of encapsulated antibiotics^{11,12,13,14,15.}

4. To create sustained-release formulations, furosemide, chlorothiazide, and sulphonamide were encapsulated, with the advantage of avoiding the short periods of peak diuresis seen with conventional formulations.^16,17

5. Antihypertensives include captopril, nicardipine, dipyridamole, piretanide and propranolol HCl, dihydralazine sulphate, and isosorbide-5-mononitrate (IS-5-MN). IS-5-MN microcapsules were prepared and adjusted in order to maintain the effect and get past the tolerance that had formed in earlier preparations.^18,19

6. Tiny particles packed with air are used in echocardiography and other ultrasonic imaging methods. They are also used as opacifiers or reflectivity enhancers in cosmetics.

7. Solid microspheres are used in the nasal administration of drugs, including insulin, somatostatin, polypeptides, and metoclopramide.

8. Among other ways, pharmaceuticals have been delivered by IV injection, intradermal injection, rectally, orally, intravaginal, inhalational administration, and mursoual delivery using PH-activated microparticles.

9. Medication administration is another use for them. The antigenic epitote of a pathogen or tumor.

10. Gene therapy and cell transfection may benefit from the microscopic particles.11. Enzymes, antibodies, and dyes are employed as stable, robust kits with condensed phase microparticles²⁰.

CONCLUSION:

Microspheres are the most popular drug delivery technology due to their advantages in terms of bioavailability, reduced frequency of dosing, improved stability, sustained and controlled release action, and dissolving rate. The medication is precisely delivered to the target site and maintained at the place of interest with the help of spherical microspheres, all without causing any undesirable side effects. The special polymeric microspheres hold the medication. Membrane, which is situated in the center of the particle. Microspheres are a better option for drug delivery systems (DDS) than many other types. As the tiny replicas of diseased tissues and organs in the body, microspheres will play a major and central role in novel drug delivery in the future by combining a variety of other strategies, particularly in diagnostics, diseased cell sorting, gene and genetic materials, targeted, safe, effective and specific in vitro delivery and supplements.

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Received on 12.04.2024 Modified on 30.05.2024

Asian J. Pharm. Res. 2024; 14(3):285-288.

DOI: 10.52711/2231-5691.2024.00044