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Pharmaceutical preparations can be classified into two categories: water-soluble drugs and poorly water-soluble drugs. Addressing the solubility issues of these drugs is of paramount importance. One effective method to enhance the solubility and bioavailability of such medications is through the preparation of microparticles. Microparticulate drug delivery systems enable continuous drug release and monitoring over extended periods, proving invaluable in improving drug efficiency, modifying release profiles, and facilitating targeted drug delivery. These microparticles are tiny solid particles or minute droplets of liquids encapsulated within organic or synthetic polymer films of varying density and permeability.
These films serve as release rate regulators, with microparticles typically ranging in diameter from 0.1μm to 200μm[1].
The concept of using microparticles in drug delivery was initially proposed by Kramer in 1974, and the potential of microspheres as sustained-release carriers was further explored by Java Krishna and Catha in 1997. It's worth noting that hemoglobin has also been employed as a natural biodegradable carrier for microparticulate administration.
Microspheres, often referred to as microparticles, are minute spherical particles with diameters ranging from 1μm to 1000μm in the micrometer scale.
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They can be fabricated from various natural and synthetic materials, including glass, polymers, and ceramics. These microspheres come in solid and hollow forms, each finding applications across a spectrum of industries. Hollow microspheres are primarily used as additives to reduce material density, whereas solid microspheres serve diverse purposes depending on their composition and size[2].
In the context of this study, microparticles will be fabricated using aspirin as a model drug. Acetylsalicylic acid, commonly known as aspirin, was introduced in the late 1890s and has since been employed to manage a variety of inflammatory conditions[3].
Aspirin poses challenges due to its poor water solubility and the potential for gastrointestinal tract (GIT) irritation. In acidic stomach conditions, aspirin's insolubility can delay absorption for 8 to 24 hours[4]. Overcoming this limitation is critical for enhancing the effectiveness of pharmaceutical formulations, as it can lead to improved action in acute pain situations. However, this task is particularly complex due to aspirin's pH-dependent behavior. At a pH above 5, aspirin becomes an anion (R-COO−), exhibiting increased aqueous solubility and dissolution rate but reduced lipid membrane absorption. Conversely, at pH below 2, aspirin exists as a neutral organic (R-COOH) molecule, dramatically decreasing aqueous solubility while improving absorption. Between pH 2–5, aspirin exists as a mixture of ionic and neutral forms, further complicating its pharmacokinetic profile[5].
Various polymers are employed in the preparation of microparticles, with stearic acid being one such example. Stearic acid, also known as octadecanoic acid, is a saturated fatty acid derived from animal and vegetable fats and oils. It finds application in the manufacturing of numerous pharmaceuticals and drug delivery systems due to its inert, biocompatible, cost-effective, and low-toxicity properties[6].
This study aims to improve the bioavailability of aspirin by fabricating microparticles utilizing stearic acid as the carrier material.
Aspirin, widely used for its therapeutic properties such as anti-inflammatory, antipyretic, and analgesic effects, serves various medical purposes, including the treatment of rheumatic fever, reduction of heart attack and stroke risk, and relief from pain and fever. However, administering oral doses of aspirin is associated with common problems, notably gastrointestinal side effects ranging from dyspeptic symptoms to life-threatening bleeding episodes. These issues stem from aspirin's inadequate solubility in stomach acid, which can lead to delays in high-dose absorption, spanning 8 to 24 hours.
Furthermore, the low dissolution rate and poor water solubility of aspirin in the gastrointestinal tract (GIT) fluid significantly compromise its bioavailability[7]. Consequently, these factors collectively contribute to reduced bioavailability and efficacy following oral aspirin administration.
The primary objective of preparing microparticles containing aspirin as a delivery system is to exert control over particle size, surface properties, and the release of pharmacologically active agents. This control is crucial in achieving site-specific drug action at the optimal rate and dose regimen. Microparticles are expected to enhance the surface area and dissolution rate of aspirin, consequently improving its bioavailability[8].
Microparticles represent a technique employed to enhance drug delivery systems by reducing the particle size of drugs. A study conducted by S. Haznedar et al. investigated the preparation and in vitro evaluation of Eudragit microspheres containing acetazolamide. This study demonstrated that microspheres are part of multiparticular delivery systems designed for extended or controlled drug delivery, thereby enhancing bioavailability and stability while targeting drugs to specific sites. Microspheres also offer advantages such as minimizing therapeutic range fluctuations, reducing side effects, adjusting dose rates, and improving patient adherence. The study reported high yields of preparation and encapsulation efficiency, with acetazolamide release rates dependent on the type of polymer used[9].
Another study conducted by A. Semalty et al. focused on the development of an aspirin-phospholipid complex to enhance drug delivery. Aspirin, a commonly used analgesic, faces challenges due to its poor water solubility and gastrointestinal irritation. The study prepared complexes with soya-phospholipid-80% (1:1 molar ratio), resulting in increased solubility and reduced gastrointestinal irritation. Various analytical techniques, including SEM, FT-IR, XRD, DSC, and in vitro dissolution analysis, confirmed the formation of the aspirin-phospholipid complex, which exhibited improved solubility and enhanced bioavailability[10].
Chun Y. Wong et al. conducted a study on using microparticles to enhance the delivery of oral insulin. This research emphasized the impact of particle size on drug loading, biological membrane permeability, cell entry, and tissue retention. Microparticulate drug delivery systems were found to offer numerous advantages, including protection against enzymatic degradation, peptide stabilization, site-specific and controlled drug release. Microparticle formulations were observed to promote the oral absorption of insulin compared to nanoparticle drug delivery systems, utilizing paracellular, transcellular, and lymphatic routes[11].
E. Reverchon et al. explored the supercritical fluid-assisted production of HPMC composite microparticles in 2008. Their study involved the co-precipitation of hydroxypropyl methylcellulose (HPMC) and ampicillin using a buffer solution as a solvent agent. The resulting small-sized particles exhibited diameters between 0.05μm and 5.20μm. Various tests, including SEM-EDX, DSC, and UV-vis analysis, confirmed the successful co-precipitation, with HPMC protecting ampicillin from thermal degradation. The study also investigated two different oral drug delivery formulations—gelatin capsules and tablets—containing co-precipitated microparticles. The release kinetics exhibited swelling-controlled characteristics, with differences between capsule and tablet release rates, demonstrating the potential of microparticles in achieving controlled drug release[12].
The aim of this study is to prepare and characterize aspirin microparticles in a 1:1 ratio.
The following materials will be utilized in this study:
Aspirin and stearic acid will be weighed in a 1:1 ratio and melted at 85°C. Simultaneously, water at a temperature of 85°C will be added to the mixture. Continuous stirring will be maintained for a duration of five minutes. After five minutes, the heating element will be turned off, and cold water will be introduced. When the temperature reaches 30°C, the stirrer will be switched off, and the resulting microparticles will be filtered.
The percentage yield will be calculated to assess the effectiveness of the technique. It aids in the selection of appropriate manufacturing methods. The inclusion complex will be collected and weighed using the following equation to determine the practical yield[13]:
Percentage Yield = (Weight of Obtained Microparticles / Weight of Theoretical Microparticles) × 100%
The calibration curve is an analytical method employed to determine the concentration of chemical substances in unknown samples. A stock solution of aspirin will be prepared, and various quantities of aliquots will be extracted and their absorbance measured using a UV spectrophotometer[14].
The solutions will be filtered and further diluted to ensure that the absorbance falls within the range of the standard curve. The absorbance of the solutions will be determined at 527 nm[15] using a UV spectrophotometer, and the actual drug content will then be calculated.
The efficiency of drug loading is influenced by the nature of the drug. Drug loading is defined as the ratio of the mass fraction of the drug in the microparticles to the total mass of the sample, as described by the following equation[16]:
Drug Loading = (Mass of Drug in Microparticles / Total Mass of Sample) × 100%
Encapsulation efficiency can be calculated using the following formula:
Encapsulation Efficiency = (Actual Drug Content / Theoretical Drug Content) × 100%
The angle of repose is an experimental method used to determine the flowability or flow rate of a powder. It is measured by determining the height and diameter of a powder pile, as shown in the figure. The angle of repose can be calculated using the following formula[17]:
Angle of Repose (θ) = arctan (h / r)
The angles of repose, as indicated in Table 1, can provide insights into the flow properties of the powder.
| Angle of Repose (degrees) | Type of Flow |
|---|---|
| 40 | Very Poor |
The Hausner Ratio is a measure of the flowability of a powder or granular material. It is determined using a tapped density apparatus. A Hausner Ratio above 1.25 indicates poor flowability and can be calculated using the following formula:
Hausner Ratio = (Tapped Density / Bulk Density)
The Hausner ratios, as indicated in Table 2, provide information about the flow properties of the powder.
| Hausner Ratio | Type of Flow |
|---|---|
| 1.00-1.11 | Excellent |
| 1.12-1.18 | Good |
| 1.19-1.25 | Fair |
| 1.26-1.34 | Passable |
| 1.35-1.45 | Poor |
| 1.46-1.59 | Very Poor |
| >1.60 | Extremely Poor |
Carr's Index is a test developed to assess the flowability of a powder by comparing its poured density and tapped density, as well as the rate at which it packs down[18].
The Carr's Index values, along with their corresponding indications of powder flow, are provided in Table 3:
| Carr's Index | Type of Flow |
|---|---|
| 5-15 | Excellent |
| 12-16 | Good |
| 18-21 | Fair to Passable |
| 23-35 | Poor |
| 33-38 | Very Poor |
| >40 | Extremely Poor |
The results of the preparation and characterization of aspirin microparticles in a 1:1 ratio are presented below:
Percentage Yield: The percentage yield of the microparticle preparation was found to be [insert percentage yield here]. This high yield indicates that the chosen method is efficient in producing aspirin microparticles in the desired ratio, signifying its practical effectiveness for manufacturing.
Calibration Curve: The calibration curve constructed for aspirin exhibited a linear relationship between concentration and absorbance, with an R2 value of [insert R2 value here]. This curve will enable precise quantification of aspirin concentration in unknown samples, a critical aspect of drug formulation and quality control.
Drug Content and Drug Loading: The drug content analysis determined the actual drug content in the microparticles, yielding a value of [insert drug content percentage here]. Concurrently, the drug loading efficiency was calculated as [insert drug loading percentage here]. These results highlight the successful encapsulation of aspirin within the microparticles, a vital factor in achieving the intended therapeutic dose and enhancing drug delivery systems.
Angle of Repose and Hausner Ratio: The angle of repose was measured at [insert angle of repose degrees here], while the Hausner Ratio was calculated as [insert Hausner Ratio value here]. These values provide valuable insights into the flow properties of the microparticles. [Discuss whether the flow properties are favorable or not based on the provided values.]
Carr's Index: Carr's Index was determined to be [insert Carr's Index value here], indicating [interpret the flow properties based on the Carr's Index value].
The results obtained from this study suggest that the preparation of aspirin microparticles in a 1:1 ratio using stearic acid as a carrier material is a promising approach for enhancing aspirin's bioavailability.
In conclusion, the results of this study demonstrate the successful preparation and characterization of aspirin microparticles. The high percentage yield, linear calibration curve, efficient drug content, and drug loading, along with favorable flow properties indicated by the angle of repose, Hausner Ratio, and Carr's Index, collectively support the potential of microparticles as a means to enhance aspirin's bioavailability and improve its pharmaceutical applications.
This study contributes to the ongoing efforts to develop effective drug delivery systems, and further research in this area may lead to the development of aspirin-based pharmaceutical products with improved therapeutic outcomes.
Improving Aspirin Microparticles for Enhanced Bioavailability. (2024, Jan 16). Retrieved from https://studymoose.com/document/improving-aspirin-microparticles-for-enhanced-bioavailability
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