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    <import namespace="http://fasb.org/us-gaap/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd" />
    <import namespace="http://fasb.org/us-types/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-types-2025.xsd" />
    <import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd" />
    <import namespace="http://xbrl.sec.gov/country/2025" schemaLocation="https://xbrl.sec.gov/country/2025/country-2025.xsd" />
    <import namespace="http://fasb.org/srt/2025" schemaLocation="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd" />
    <import namespace="http://fasb.org/srt-types/2025" schemaLocation="https://xbrl.fasb.org/srt/2025/elts/srt-types-2025.xsd" />
    <element id="PTIX_CommonStockPurchaseWarrantMember" name="CommonStockPurchaseWarrantMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SeriesBConvertiblePreferredStockMember" name="SeriesBConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SeriesCConvertiblePreferredStockMember" name="SeriesCConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SeriesC1ConvertiblePreferredStockMember" name="SeriesC1ConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SeriesDConvertiblePreferredStockMember" name="SeriesDConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SeriesAConvertiblePreferredStockMember" name="SeriesAConvertiblePreferredStockMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_StockPurchaseAgreementMember" name="StockPurchaseAgreementMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ABTIPharmaMember" name="ABTIPharmaMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_PhytanixBioMember" name="PhytanixBioMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_AlterolaAndEmc2Member" name="AlterolaAndEmc2Member" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SeriesAConvertiblePreferredSharesMember" name="SeriesAConvertiblePreferredSharesMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_PhytanixBioIncMember" name="PhytanixBioIncMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SeriesCOnePreferredStockMember" name="SeriesCOnePreferredStockMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_AssembledWorkforceMember" name="AssembledWorkforceMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SecuritiesPurchaseAgreementsMember" name="SecuritiesPurchaseAgreementsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SeriesAPreferredWarrantsMember" name="SeriesAPreferredWarrantsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SeriesBPreferredWarrantsMember" name="SeriesBPreferredWarrantsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_CommonWarrantMember" name="CommonWarrantMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ProtagenicTherapeuticsIncMember" name="ProtagenicTherapeuticsIncMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ABTIPharmaLimitedMember" name="ABTIPharmaLimitedMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_TwoThousandSixteenPlanMember" name="TwoThousandSixteenPlanMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_EmployeesMember" name="EmployeesMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_NonEmployeesMember" name="NonEmployeesMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_TwoThousandSixEquityIncentivePlanMember" name="TwoThousandSixEquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_TwoThousandSixteenEquityIncentivePlanMember" name="TwoThousandSixteenEquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ResearchAgreementsMember" name="ResearchAgreementsMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_AxiomRealTimeMetricsIncMember" name="AxiomRealTimeMetricsIncMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_AccountingAndAuditFees" name="AccountingAndAuditFees" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_WriteOffOfReceivables" name="WriteOffOfReceivables" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_DerivativeGainLossOnDerivativeNetAndFairValueAdjustmentOfWarrants" name="DerivativeGainLossOnDerivativeNetAndFairValueAdjustmentOfWarrants" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ForeignCurrencyExchangeDifferences" name="ForeignCurrencyExchangeDifferences" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_OtherComprehensiveIncomeLossNetUnrealizedLossOnMarketableSecurities" name="OtherComprehensiveIncomeLossNetUnrealizedLossOnMarketableSecurities" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_CashReceivedForFoundersSharesAmount" name="CashReceivedForFoundersSharesAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_StockIssuedDuringPeriodValuePreferredStockToOfficers" name="StockIssuedDuringPeriodValuePreferredStockToOfficers" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_StockIssuedDuringPeriodSharesPreferredStockToOfficers" name="StockIssuedDuringPeriodSharesPreferredStockToOfficers" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_StockIssuedDuringPeriodValueReverseMerger" name="StockIssuedDuringPeriodValueReverseMerger" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_StockIssuedDuringPeriodSharesReverseMerger" name="StockIssuedDuringPeriodSharesReverseMerger" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_StockIssuedDuringPeriodValueBioPurchase" name="StockIssuedDuringPeriodValueBioPurchase" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_StockIssuedDuringPeriodSharesBioPurchase" name="StockIssuedDuringPeriodSharesBioPurchase" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_StockIssuedDuringPeriodValueWarrantExercise" name="StockIssuedDuringPeriodValueWarrantExercise" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_StockIssuedDuringPeriodSharesWarrantExercise" name="StockIssuedDuringPeriodSharesWarrantExercise" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_AdjustmentIncreaseInNotePayableForAcquisitionOfPhytanixBio" name="AdjustmentIncreaseInNotePayableForAcquisitionOfPhytanixBio" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_IncreaseDecreaseInValueAddedTaxReceivable" name="IncreaseDecreaseInValueAddedTaxReceivable" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_NetAssetsAcquiredOfPhytanixBioNetOfCashReceived" name="NetAssetsAcquiredOfPhytanixBioNetOfCashReceived" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_DisclosureLiquidityAndGoingConcernAbstract" name="DisclosureLiquidityAndGoingConcernAbstract" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_LiquidityAndGoingConcernDisclosureTextBlock" name="LiquidityAndGoingConcernDisclosureTextBlock" nillable="true" xbrli:periodType="duration" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_WorkingCapitalDeficit" name="WorkingCapitalDeficit" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ResearchAndDevelopmentCurrent" name="ResearchAndDevelopmentCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_LegalCurrent" name="LegalCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_CompensationCurrent" name="CompensationCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_GeneralAndAdministrativeCurrent" name="GeneralAndAdministrativeCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_AccruedResearchAndDevelopment" name="AccruedResearchAndDevelopment" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_RecognitionOfConversionOptionOnNotesPayable" name="RecognitionOfConversionOptionOnNotesPayable" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice" nillable="true" xbrli:periodType="instant" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageRemainingContractualTerm" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageRemainingContractualTerm" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsInPeriodWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsInPeriodWeightedAverageExercisePrice" nillable="true" xbrli:periodType="duration" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExpirationsInPeriodWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExpirationsInPeriodWeightedAverageExercisePrice" nillable="true" xbrli:periodType="duration" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisedInPeriodWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisedInPeriodWeightedAverageExercisePrice" nillable="true" xbrli:periodType="duration" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquitySharesIssued" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquitySharesIssued" nillable="true" xbrli:periodType="instant" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionsEquityOutstandingWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionsEquityOutstandingWeightedAverageExercisePrice" nillable="true" xbrli:periodType="instant" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsNonOptionsAggregateIntrinsicValueOutstanding" name="SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsNonOptionsAggregateIntrinsicValueOutstanding" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_RoyaltyPaymentPercentage" name="RoyaltyPaymentPercentage" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_UpFrontSubLicenseFeesPercentage" name="UpFrontSubLicenseFeesPercentage" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_RoyaltyPaymentOnBehalfOfSublicenseePercentage" name="RoyaltyPaymentOnBehalfOfSublicenseePercentage" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_InterestOnAmountsOwedUnderLicenseAgreementRate" name="InterestOnAmountsOwedUnderLicenseAgreementRate" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_BidPriceRequirement" name="BidPriceRequirement" nillable="true" xbrli:periodType="instant" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_ClosingBidPrice" name="ClosingBidPrice" nillable="true" xbrli:periodType="instant" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_RemainingSharesOfPublicFloat" name="RemainingSharesOfPublicFloat" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_MinimumBidPrice" name="MinimumBidPrice" nillable="true" xbrli:periodType="instant" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="PTIX_RecognizedDerivativeExpense" name="RecognizedDerivativeExpense" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
</schema>
